Logo

Programming-Idioms.org

  • The snippets are under the CC-BY-SA license.
  • Consider printing in landscape mode
  • or not printing at all, and keeping a bookmark.
Java Go
1
Print a literal string on standard output
System.out.println("Hello World");
fmt.Println("Hello World")
2
Loop to execute some code a constant number of times
for(int i=0;i<10;i++)
  System.out.println("Hello");
Alternative implementation:
System.out.print("Hello\n".repeat(10));
for i := 0; i < 10; i++ {
	fmt.Println("Hello")
}
3
Like a function which doesn't return any value, thus has only side effects (e.g. Print to standard output)
void finish(String name){
  System.out.println("My job here is done. Goodbye " + name);
}
func finish(name string) {
  fmt.Println("My job here is done. Good bye " + name)
}
4
int square(int x){
  return x*x;
}
func square(x int) int {
  return x*x
}
5
Declare a container type for two floating-point numbers x and y
class Point{
  double x;
  double y;
}
type Point struct {
    x, y float64
}
6
Do something with each item x of an array-like collection items, regardless indexes.
for (Item x: items) {
    doSomething(x);
}
Alternative implementation:
for(int i=0;i<items.length;i++){
	doSomething( items[i] );
}
Alternative implementation:
items.stream().forEach(item -> doSomething(item));
for _, x := range items {
    doSomething(x)
}
7
Print each index i with its value x from an array-like collection items
for (int i = 0; i < items.length; i++) {
    T x = items[i];
    System.out.printf("Item %d = %s%n", i, x);
}
Alternative implementation:
for (int i = 0; i < items.size(); i++) {
    T x = items.get(i);
    System.out.printf("Item %d = %s%n", i, x);
}
for i, x := range items {
    fmt.Printf("Item %d = %v \n", i, x)
}
8
Create a new map object x, and provide some (key, value) pairs as initial content.
Map<String,Integer> x = new HashMap<>();
x.put("one", 1);
x.put("two", 2);
Alternative implementation:
final Map<String, Integer> x = new HashMap<String, Integer>() {{
    put("one", 1);
    put("two", 2);
    put("three", 3);
}};
x := map[string]int {"one": 1, "two": 2}
9
The structure must be recursive because left child and right child are binary trees too. A node has access to children nodes, but not to its parent.
class BinTree<T extends Comparable<T>>{
   T value;
   BinTree<T> left;
   BinTree<T> right;
}
Alternative implementation:
interface Tree<T>{
    boolean search(T x);
}
class Nil<T extends Comparable<? super T>> implements Tree<T>{
    public boolean search(T x) { return false; }
}
class Node<T extends Comparable<? super T>> implements Tree<T> {
 T item;  Tree<T> left; Tree<T> right;
 public Node(T i, Tree<T> l, Tree<T> r) {
     item=i;  left=l;  right=r; }
 public boolean search(T x) {
     int cmp = x.compareTo(item);
     return cmp==0 || (cmp<0 && left.search(x)) || (cmp>0 && right.search(x));
 }
type BinTree struct {
	Value valueType
	Left *BinTree
	Right *BinTree
}
10
Generate a random permutation of the elements of list x
Collections.shuffle(x);
for i := range x {
	j := rand.Intn(i + 1)
	x[i], x[j] = x[j], x[i]
}
Alternative implementation:
y := make([]T, len(x))
perm := rand.Perm(len(x))
for i, v := range perm {
	y[v] = x[i]
}
Alternative implementation:
rand.Shuffle(len(x), func(i, j int) {
	x[i], x[j] = x[j], x[i]
})
Alternative implementation:
for i := len(x) - 1; i > 0; i-- {
	j := rand.Intn(i + 1)
	x[i], x[j] = x[j], x[i]
}
11
List x must be non-empty.
x.get((int)(Math.random()*x.size()))
Alternative implementation:
x.get(ThreadLocalRandom.current().nextInt(0, x.size()))
x[rand.Intn(len(x))]
Alternative implementation:
func pickT(x []T) T {
	return x[rand.Intn(len(x))]
}
12
Check if list contains a value x.
list is an iterable finite container.
boolean contains(int[] list, int x){
  for(int y:list)
    if( y==x )
      return true;
  return false;
}
Alternative implementation:
boolean <T> contains(T[] list, T x){
  if( x==null){
    for(T y:list)
      if( y==null )
        return true;
  }else{
    for(T y:list)
      if( x.equals(y) )
        return true;
  }
  return false;
}
Alternative implementation:
list.contains(x)
func Contains(list []T, x T) bool {
	for _, item := range list {
		if item == x {
			return true
		}
	}
	return false
}
13
Access each key k with its value x from an associative array mymap, and print them.
for (Map.Entry<Object, Object> entry : mymap.entrySet()) {
    Object k = entry.getKey();
    Object x = entry.getValue();
    System.out.println("Key=" + k + ", Value=" + x);
}
Alternative implementation:
mymap.forEach((k,x) -> System.out.println("Key=" + k + ", Value=" + x));
for k, x := range mymap {
  fmt.Println("Key =", k, ", Value =", x)
}
14
Pick a random number greater than or equals to a, strictly inferior to b. Precondition : a < b.
double pick(double a, double b){
	return a + (Math.random() * (b-a));
}
func pick(a, b  float64)  float64 {
	return a + (rand.Float64() * (b-a))
}
15
Pick a random integer greater than or equals to a, inferior or equals to b. Precondition : a < b.
int pick(int a, int b){
	return a + new Random().nextInt(b - a + 1);
}
func pick(a,b int) int {
	return a + rand.Intn(b-a+1)
}
16
Call a function f on every node of binary tree bt, in depth-first infix order
void dfs(BinTree bt) {
	if (bt.left != null) {
		dfs(bt.left);
        }
	f(bt);
	if (bt.right != null) {
		dfs(bt.right);
        }
}
Alternative implementation:
class BinTree {
	// ...

	void dfs() {
		if( left != null )
			left.dfs();
		f(this);
		if( right != null )
			right.dfs();
	}
}
Alternative implementation:
class BinTree<T> {
	// ...

	void dfs(Consumer<BinTree<T>> f) {
		if( left != null )
			left.dfs(f);
		f.accept(this);
		if( right != null )
			right.dfs(f);
	}
}
func (bt *BinTree) Dfs(f func(*BinTree)) {
	if bt == nil {
		return
	}
	bt.Left.Dfs(f)
	f(bt)
	bt.Right.Dfs(f)
}
17
The structure must be recursive. A node may have zero or more children. A node has access to children nodes, but not to its parent.
class Tree<K,V> {
  K key;
  V deco;
  List<Tree<K,V>> children = new ArrayList<>();
}
type Tree struct {
	Key keyType
	Deco valueType
	Children []*Tree
}
18
Call a function f on every node of a tree, in depth-first prefix order
func (t *Tree) Dfs(f func(*Tree)) {
	if t == nil {
		return
	}
	f(t)
	for _, child := range t.Children {
		child.Dfs(f)
	}
}
19
Reverse the order of the elements of list x.
This may reverse "in-place" and destroy the original ordering.
static <T> void reverse(List<T> x){
	int n = x.size();
	for(int i=0;i<n/2;i++){
		T tmp = x.get(i);
		x.set(i, x.get(n-i-1));
		x.set(n-i-1, tmp);
	}
}
Alternative implementation:
Collections.reverse(x);
Alternative implementation:
Collections.reverse(x);
for i, j := 0, len(x)-1; i < j; i, j = i+1, j-1 {
	x[i], x[j] = x[j], x[i]
}
20
Implement a function search which looks for item x in a 2D matrix m.
Return indices i, j of the matching cell.
Think of the most idiomatic way in the language to return the two values at the same time.
static class Position{
	int i;
	int j;
}

Position search(int[][] m, int x){
	for(int i=0;i<m.length;i++)
		for(int j=0;j<m[i].length;j++)
			if(m[i][j] == x){
				Position pos= new Position();
				pos.i = i;
				pos.j = j;
				return pos;
			}
	return null;
}
func search(m [][]int, x int) (bool, int, int) {
	for i := range m {
		for j, v := range m[i] {
			if v == x {
				return true, i, j
			}
		}
	}
	return false, 0, 0
}
21
Swap values of variables a and b
T tmp = a;
a = b;
b = tmp;
a, b = b, a
22
Extract integer value i from its string representation s (in radix 10)
int i = Integer.parseInt(s);
Alternative implementation:
int i = new Integer(s).intValue();
i, err  := strconv.Atoi(s) 
Alternative implementation:
i, err := strconv.ParseInt(s, 10, 0)
23
Given real number x, create its string representation s with 2 decimal digits following the dot.
String s = String.format("%.2f", x);
s := fmt.Sprintf("%.2f", x)
24
Declare a new string s and initialize it with the literal value "ネコ" (which means "cat" in japanese)
String s = "ネコ";
s := "ネコ"
25
Share the string value "Alan" with an existing running process which will then display "Hello, Alan"
https://gist.github.com/f7c174c53efaba4d8575
ch <- "Alan"
26
Declare and initialize a matrix x having m rows and n columns, containing real numbers.
double[][] x = new double[m][n];
const m, n = 3, 4
var x [m][n]float64
Alternative implementation:
func make2D(m, n int) [][]float64 {
	buf := make([]float64, m*n)

	x := make([][]float64, m)
	for i := range x {
		x[i] = buf[:n:n]
		buf = buf[n:]
	}
	return x
}
27
Declare and initialize a 3D array x, having dimensions boundaries m, n, p, and containing real numbers.
double[][][] x = new double[m][n][p];
const m, n, p = 2, 2, 3
var x [m][n][p]float64
Alternative implementation:
func make3D(m, n, p int) [][][]float64 {
	buf := make([]float64, m*n*p)

	x := make([][][]float64, m)
	for i := range x {
		x[i] = make([][]float64, n)
		for j := range x[i] {
			x[i][j] = buf[:p:p]
			buf = buf[p:]
		}
	}
	return x
}
28
Sort elements of array-like collection items in ascending order of x.p, where p is a field of the type Item of the objects in items.
Arrays.sort(items, new Comparator<Item>(){
	public int compare(Item a, Item b){
		return a.p - b.p;
	}
});
Alternative implementation:
Collections.sort(items, new Comparator<Item>(){
	@Override
	public int compare(Item a, Item b){
		return a.p - b.p;
	}
});
Alternative implementation:
items.stream().sorted(Comparator.comparing(x -> x.p))
type ItemPSorter []Item
func (s ItemPSorter) Len() int{ return len(s) }
func (s ItemPSorter) Less(i,j int) bool{ return s[i].p<s[j].p }
func (s ItemPSorter) Swap(i,j int) { s[i],s[j] = s[j],s[i] }

func sortItems(items []Item){
	sorter := ItemPSorter(items)
	sort.Sort(sorter)
}
Alternative implementation:
less := func(i, j int) bool {
	return items[i].p < items[j].p
}
sort.Slice(items, less)
29
Remove i-th item from list items.
This will alter the original list or return a new list, depending on which is more idiomatic.
Note that in most languages, the smallest valid value for i is 0.
items.remove(i);
items = append(items[:i], items[i+1:]...)
Alternative implementation:
copy(items[i:], items[i+1:])
items[len(items)-1] = nil
items = items[:len(items)-1]
30
Launch the concurrent execution of procedure f with parameter i from 1 to 1000.
Tasks are independent and f(i) doesn't return any value.
Tasks need not run all at the same time, so you may use a pool.
final ExecutorService executor = Executors.newFixedThreadPool(NB_THREADS);
for (int i = 1; i <= 1000; i++) {
  executor.submit(() -> f(i));
}
executor.shutdown();
wg := sync.WaitGroup{}
wg.Add(1000)
for i := 1; i <= 1000; i++ {
	go func(j int) {
          f(j)
          wg.Done()
        }(i)
}
wg.Wait()
31
Create recursive function f which returns the factorial of non-negative integer i, calculated from f(i-1)
int f(int i){
	if(i==0)
		return 1;
	else
		return i * f(i-1);
} 
func f(i int) int {
  if i == 0 {
    return 1
  }
  return i * f(i-1)
}
32
Create function exp which calculates (fast) the value x power n.
x and n are non-negative integers.
int exp(int x, int n){
	if(n==0)
		return 1;
	if(n==1)
		return x;
	if(n%2==0)
		return exp(x*x, n/2);
	else
		return x * exp(x*x, (n-1)/2);
}
func exp(x, n int) int {
	switch {
	case n == 0:
		return 1
	case n == 1:
		return x
	case n%2 == 0:
		return exp(x*x, n/2)
	default:
		return x * exp(x*x, (n-1)/2)
	}
}
33
Assign variable x the new value f(x), making sure that no other thread may modify x between the read and the write.
synchronized(lock){
  x = f(x);
}
var lock sync.RWMutex

lock.Lock()
x = f(x)
lock.Unlock()
34
Declare and initialize a set x containing objects of type T.
Set<T> x = new HashSet<T>();
Alternative implementation:
Set<T> x = new HashSet<T>();
x.add(a);
x.add(b);
x := make(map[T]bool)
Alternative implementation:
x := make(map[T]struct{})
35
Implement a function compose (A -> C) with parameters f (A -> B) and g (B -> C), which returns composition function g ∘ f
public <A,B,C> Function<A,C> compose(Function<A,B> f, Function<B,C> g){
   return x -> g.apply(f.apply(x));
}
Alternative implementation:
Function<Integer, Integer> addOne = i-> i + 1;
Function<Integer, String> toString = i-> i.toString();
Function<Integer, String> printIncremented = toString.compose(addOne);
func compose(f func(A) B, g func(B) C) func(A) C {
	return func(x A) C {
		return g(f(x))
	}
}
36
Implement a function compose which returns composition function g ∘ f for any functions f and g having exactly 1 parameter.
    default <V> Function<V, R> compose(Function<? super V, ? extends T> before) {
        Objects.requireNonNull(before);
        return (V v) -> apply(before.apply(v));
    }
func composeIntFuncs(f func(int) int, g func(int) int) func(int) int {
	return func(x int) int {
		return g(f(x))
	}
}
37
Transform a function that takes multiple arguments into a function for which some of the arguments are preset.
IntBinaryOperator simpleAdd = (a, b) -> a + b;
IntFunction<IntUnaryOperator> curriedAdd = a -> b -> a + b;
System.out.println(simpleAdd.applyAsInt(4, 5));
System.out.println(curriedAdd.apply(4).applyAsInt(5));
type PayFactory func(Company, *Employee, *Employee) Payroll

type CustomPayFactory func(*Employee) Payroll

func CurryPayFactory(pf PayFactory,company Company, boss *Employee) CustomPayFactory {
	return func(e *Employee) Payroll {
		return pf(company, boss, e)
	}
}
38
Find substring t consisting in characters i (included) to j (excluded) of string s.
Character indices start at 0 unless specified otherwise.
Make sure that multibyte characters are properly handled.
String t = s.substring(i,j);
t := string([]rune(s)[i:j])
39
Set boolean ok to true if string word is contained in string s as a substring, or to false otherwise.
boolean ok = s.contains(word);
ok := strings.Contains(s, word)
40
Declare a Graph data structure in which each Vertex has a collection of its neighbouring vertices.
class Graph{
  List<Vertex> vertices;

  static class Vertex{
    int id;
    List<Vertex> neighbours;
  }
}
Alternative implementation:
class Graph{
  Set<Vertex> vertices;

  static class Vertex{
    int id;
    Set<Vertex> neighbours;
  }
}
type Vertex struct{
	Id int
	Label string
	Neighbours map[*Vertex]bool
}

type Graph []*Vertex
41
Create string t containing the same characters as string s, in reverse order.
Original string s must remain unaltered. Each character must be handled correctly regardless its number of bytes in memory.
String t = new StringBuilder(s).reverse().toString();
runes := []rune(s)
for i, j := 0, len(runes)-1; i < j; i, j = i+1, j-1 {
   runes[i], runes[j] = runes[j], runes[i]
}
t := string(runes)
42
Print each item v of list a which in not contained in list b.
For this, write an outer loop to iterate on a and an inner loop to iterate on b.
mainloop: for(int v:a){
	for(int w:b){
		if(v==w)
			continue mainloop;
	}
	System.out.println(v);
}
mainloop:
	for _, v := range a {
		for _, w := range b {
			if v == w {
				continue mainloop
			}
		}
		fmt.Println(v)
	}
43
Look for a negative value v in 2D integer matrix m. Print it and stop searching.
mainloop: for(int i=0;i<m.length;i++)
	for(int j=0;j<m[i].length;j++)
		if(m[i][j]<0){
			System.out.println(m[i][j]);
			break mainloop;
		}
mainloop:
	for i, line := range m {
		for _, v := range line {
			if v < 0 {
				fmt.Println(v)
				break mainloop
			}
		}
	}
44
Insert element x at position i in list s. Further elements must be shifted to the right.
s.add(i, x);
s = append(s, 0)
copy(s[i+1:], s[i:])
s[i] = x
45
Sleep for 5 seconds in current thread, before proceeding with next instructions.
Thread.sleep(5000);
Alternative implementation:
TimeUnit.SECONDS.sleep(5);
time.Sleep(5 * time.Second)
46
Create string t consisting of the 5 first characters of string s.
Make sure that multibyte characters are properly handled.
String t = s.substring(0,5);
t := string([]rune(s)[:5])
47
Create string t consisting in the 5 last characters of string s.
Make sure that multibyte characters are properly handled.
int n = s.length();
String t = s.substring(n-5,n);
t := string([]rune(s)[len([]rune(s))-5:])
48
Assign to variable s a string literal consisting in several lines of text, including newlines.
String s = "This is a very long string which needs \n" +
           "to wrap across multiple lines because \n" +
           "otherwise my code is unreadable.";
Alternative implementation:
String s = """
This is a very long string which needs
to wrap across multiple lines because
otherwise my code is unreadable.
""";
s := `Huey
Dewey
Louie`
49
Build list chunks consisting in substrings of input string s, separated by one or more space characters.
String[] chunks = s.split("\\s+");
chunks := strings.Split(s, " ")
Alternative implementation:
chunks := strings.Fields(s)
50
Write a loop which has no end clause.
for(;;){
	// Do something
}
Alternative implementation:
while(true) {
	// Do something	
}
for {
	// Do something
}
51
Determine whether map m contains an entry for key k
m.containsKey(k)
_, ok := m[k]
52
Determine whether map m contains an entry with value v, for some key.
m.containsValue(v)
func containsValue(m map[K]T, v T) bool {
	for _, x := range m {
		if x == v {
			return true
		}
	}
	return false
}
53
Concatenate elements of string list x joined by the separator ", " to create a single string y.
String y = String.join(", ", x);
y := strings.Join(x, ", ")
54
Calculate the sum s of integer list x.
int s = 0;
for (int i : x) {
  s += i;
}
s := 0
for _, v := range x {
	s += v
}
55
Create the string representation s (in radix 10) of integer value i.
String s=((Integer)i).toString();
Alternative implementation:
String s = Integer.toString(i);
Alternative implementation:
String s = String.valueOf(i);
Alternative implementation:
String s = "" + i;
s := strconv.Itoa(i)
Alternative implementation:
s := strconv.FormatInt(i, 10)
Alternative implementation:
s := fmt.Sprintf("%d", i)
56
Fork-join : launch the concurrent execution of procedure f with parameter i from 1 to 1000.
Tasks are independent and f(i) doesn't return any value.
Tasks need not run all at the same time, so you may use a pool.
Wait for the completion of the 1000 tasks and then print "Finished".
class Task implements Runnable {
	int i;
	Task(int i) {
		this.i = i;
	}
	@Override
	public void run() {
		f(i);
	}
}

ExecutorService executor = Executors.newFixedThreadPool(4);
for (int i = 1; i <= 1000; i++) {
	Task task = new Task(i);
	executor.submit(task);
}
executor.awaitTermination(10L, TimeUnit.MINUTES);
System.out.println("Finished");
Alternative implementation:
ExecutorService executor = Executors.newFixedThreadPool(4);
for (int i = 1; i <= 1000; i++) {
	Task task = new Task(i);
	executor.submit(() -> f(i));
}
executor.awaitTermination(10L, TimeUnit.MINUTES);
System.out.println("Finished");
var wg sync.WaitGroup
wg.Add(1000)
for i := 1; i <= 1000; i++ {
	go func(i int) {
		f(i)
		wg.Done()
	}(i)
}
wg.Wait()
fmt.Println("Finished")
57
Create list y containing items from list x satisfying predicate p. Respect original ordering. Don't modify x in-place.
var y = x.stream().filter(p).collect(Collectors.toList());
y := make([]T, 0, len(x))
for _, v := range x{
	if p(v){
		y = append(y, v)
	}
}
58
Create string lines from the content of the file with filename f.
byte[] encoded = Files.readAllBytes(Paths.get(f));
String lines = new String(encoded, StandardCharsets.UTF_8);
b, err := ioutil.ReadFile(f)
if err != nil {
	// Handle error...
}
lines := string(b)
59
Print the message "x is negative" to standard error (stderr), with integer x value substitution (e.g. "-2 is negative").
System.err.format("%d is negative\n",x);
fmt.Fprintln(os.Stderr, x, "is negative")
60
Assign to x the string value of the first command line parameter, after the program name.
String x = args[0];
x := os.Args[1]
61
Assign to variable d the current date/time value, in the most standard type.
Instant d = Instant.now();
var d time.Time = time.Now()
62
Set i to the position of string y inside string x, if exists.
int i = x.indexOf(y);
i := strings.Index(x, y)
63
Assign to x2 the value of string x with all occurrences of y replaced by z.
Assume occurrences of y are not overlapping.
String x2 = x.replace(y, z);
x2 := strings.Replace(x, y, z, -1)
64
Assign to x the value 3^247
BigInteger x = new BigInteger("3", 10).pow(247);
x := new(big.Int)
x.Exp(big.NewInt(3), big.NewInt(247), nil)
65
From real value x in [0,1], create its percentage string representation s with one digit after decimal point. E.g. 0.15625 -> "15.6%"
String s = new DecimalFormat("0.0%").format(x);
s := fmt.Sprintf("%.1f%%", 100.0*x)
66
Calculate the result z of x power n, where x is a big integer and n is a positive integer.
BigInteger z = x.pow(n);
nb := big.NewInt(int64(n))
var z big.Int
z.Exp(x, nb, nil)
67
Calculate binom(n, k) = n! / (k! * (n-k)!). Use an integer type able to handle huge numbers.
static BigInteger binom(int N, int K) {
    BigInteger ret = BigInteger.ONE;
    for (int k = 0; k < K; k++) {
        ret = ret.multiply(BigInteger.valueOf(N-k))
                 .divide(BigInteger.valueOf(k+1));
    }
    return ret;
}
z := new(big.Int)
z.Binomial(n, k)
68
Create an object x to store n bits (n being potentially large).
BitSet x = new BitSet(n);
var x *big.Int = new(big.Int)
Alternative implementation:
x := make([]bool, n)
Alternative implementation:
x := make([]uint64, (n+63)/64)
69
Use seed s to initialize a random generator.

If s is constant, the generator output will be the same each time the program runs. If s is based on the current value of the system clock, the generator output will be different each time.
Random r = new Random(s);
rand.Seed(s)
Alternative implementation:
r := rand.New(rand.NewSource(s))
70
Get the current datetime and provide it as a seed to a random generator. The generator sequence will be different at each run.
Random rand = new Random(System.currentTimeMillis());
rand.Seed(time.Now().UnixNano())
Alternative implementation:
r := rand.New(rand.NewSource(time.Now().UnixNano()))
71
Basic implementation of the Echo program: Print all arguments except the program name, separated by space, followed by newline.
The idiom demonstrates how to skip the first argument if necessary, concatenate arguments as strings, append newline and print it to stdout.
public class Echo {
    public static void main(final String... args) {
        out.println(join(" ", args));
    }
}
func main() {
    fmt.Println(strings.Join(os.Args[1:], " "))
}
73
Create a factory named fact for any sub class of Parent and taking exactly one string str as constructor parameter.
type ParentFactory func(string) Parent

var fact ParentFactory = func(str string) Parent {
	return Parent{
		name: str,
	}
}
74
Compute the greatest common divisor x of big integers a and b. Use an integer type able to handle huge numbers.
BigInteger x = a.gcd(b);
x.GCD(nil, nil, a, b)
75
Compute the least common multiple x of big integers a and b. Use an integer type able to handle huge numbers.
BigInteger a = new BigInteger("123456789");
BigInteger b = new BigInteger("987654321");
BigInteger x = a.multiply(b).divide(a.gcd(b));
gcd.GCD(nil, nil, a, b)
x.Div(a, gcd).Mul(x, b)
76
Create the string s of integer x written in base 2.

E.g. 13 -> "1101"
String s = Integer.toBinaryString(x);
s := strconv.FormatInt(x, 2)
Alternative implementation:
s := fmt.Sprintf("%b", x)
77
Declare a complex x and initialize it with value (3i - 2). Then multiply it by i.
Complex x = new Complex(-2.0, 3.0);
x = x.multiply(Complex.I);
x := 3i - 2
x *= 1i
78
Execute a block once, then execute it again as long as boolean condition c is true.
do {
	someThing();
	someOtherThing();
} while(c);
for{
   someThing()
   someOtherThing()
   if !c {
     break
   }
}
Alternative implementation:
for done := false; !done; {
	someThing()
	someOtherThing()
	done = !c()
}
79
Declare floating point number y and initialize it with the value of integer x .
float y = x;
y := float64(x)
80
Declare integer y and initialize it with the value of floating point number x . Ignore non-integer digits of x .
Make sure to truncate towards zero: a negative x must yield the closest greater integer (not lesser).
int y = (int)x;
y := int(x)
81
Declare integer y and initialize it with the rounded value of floating point number x .
Ties (when the fractional part of x is exactly .5) must be rounded up (to positive infinity).
long y = Math.round(x);
y := int(math.Floor(x + 0.5))
82
Find how many times string s contains substring t.
Specify if overlapping occurrences are counted.
int count = StringUtils.countMatches(s, t);
x := strings.Count(s, t)
83
Declare regular expression r matching strings "http", "htttp", "httttp", etc.
Pattern r = Pattern.compile("htt+p");
r := regexp.MustCompile("htt+p")
84
Count number c of 1s in the integer i in base 2.

E.g. i=6 → c=2
int c = Integer.bitCount(i);
func PopCountUInt64(i uint64) (c int) {
	i -= (i >> 1) & 0x5555555555555555
	i = (i>>2)&0x3333333333333333 + i&0x3333333333333333
	i += i >> 4
	i &= 0x0f0f0f0f0f0f0f0f
	i *= 0x0101010101010101
	return int(i >> 56)
}

func PopCountUInt32(i uint32) (n int) {
	i -= (i >> 1) & 0x55555555
	i = (i>>2)&0x33333333 + i&0x33333333
	i += i >> 4
	i &= 0x0f0f0f0f
	i *= 0x01010101
	return int(i >> 24)
}
Alternative implementation:
c := bits.OnesCount(i)
85
Write boolean function addingWillOverflow which takes two integers x, y and return true if (x+y) overflows.

An overflow may be above the max positive value, or below the min negative value.
public boolean addingWillOverflow(int x, int y){
    boolean willOverFlow = false;
    if(x > 0 && y > 0){
        if(y > (Integer.MAX_VALUE - x)){
            willOverFlow = true;
        }
    }
    if(x < 0 && y < 0){
       if(y < (Integer.MIN_VALUE - x)){
           willOverFlow = true;
       }
    }
    return willOverFlow;
}
func willAddOverflow(a, b int64) bool {
	return a > math.MaxInt64 - b
}
86
Write boolean function multiplyWillOverflow which takes two integers x, y and return true if (x*y) overflows.

An overflow may be above the max positive value, or below the min negative value.
static boolean multiplyWillOverflow(int x, int y) {
	return Integer.MAX_VALUE/x < y;
}
func multiplyWillOverflow(x, y uint64) bool {
   if x <= 1 || y <= 1 {
     return false
   }
   d := x * y
   return d/y != x
}
87
Exit immediatly.
If some extra cleanup work is executed by the program runtime (not by the OS itself), describe it.
System.exit(0);
os.Exit(0)
88
Create a new bytes buffer buf of size 1,000,000.
byte[] buf = new byte[1000000];
buf := make([]byte, 1000000)
89
You've detected that the integer value of argument x passed to the current function is invalid. Write the idiomatic way to abort the function execution and signal the problem.
throw new IllegalArgumentException("Invalid value for x:" + x);
return nil, fmt.Errorf("invalid value for x: %v", x)
90
Expose a read-only integer x to the outside world while being writable inside a structure or a class Foo.
type Foo struct {
	x int
}

func (f *Foo) X() int {
	return f.x
}
91
Read from file data.json and write its content into object x.
Assume the JSON data is suitable for the type of x.
buffer, err := ioutil.ReadFile("data.json")
if err != nil {
	return err
}
err = json.Unmarshal(buffer, &x)
if err != nil {
	return err
}
Alternative implementation:
r, err := os.Open(filename)
if err != nil {
	return err
}
decoder := json.NewDecoder(r)
err = decoder.Decode(&x)
if err != nil {
	return err
}
92
Write content of object x into file data.json.
buffer, err := json.MarshalIndent(x, "", "  ")
if err != nil {
	return err
}
err = ioutil.WriteFile("data.json", buffer, 0644)
93
Implement procedure control which receives one parameter f, and runs f.
static void control(Runnable f) {
    f.run();
}
func control(f func()) {
	f()
}
94
Print the name of the type of x. Explain if it is a static type or dynamic type.

This may not make sense in all languages.
System.out.println(((Object)x).getClass().getName());
fmt.Println(reflect.TypeOf(x))
Alternative implementation:
fmt.Printf("%T", x)
95
Assign to variable x the length (number of bytes) of the local file at path.
long x = new File(path).length();
info, err := os.Stat(path)
if err != nil {
	return err
}
x := info.Size()
96
Set boolean b to true if string s starts with prefix prefix, false otherwise.
boolean b = s.startsWith(prefix);
b := strings.HasPrefix(s, prefix)
97
Set boolean b to true if string s ends with string suffix, false otherwise.
boolean b = s.endsWith(suffix);
b := strings.HasSuffix(s, suffix)
98
Convert a timestamp ts (number of seconds in epoch-time) to a date with time d. E.g. 0 -> 1970-01-01 00:00:00
Date date = new Date(numberOfSecondsSinceEpoch  * 1000);
d := time.Unix(ts, 0)
99
Assign to string x the value of fields (year, month, day) of date d, in format YYYY-MM-DD.
String x = new SimpleDateFormat("yyyy-MM-dd").format(d);
Alternative implementation:
String x = String.format("%1$tY-%1$tm-%1$td", d)
x := d.Format("2006-01-02")
100
Sort elements of array-like collection items, using a comparator c.
Arrays.sort(items, c);
Alternative implementation:
Collections.sort(items, c);
type ItemCSorter []Item
func (s ItemCSorter) Len() int           { return len(s) }
func (s ItemCSorter) Less(i, j int) bool { return c(s[i], s[j]) }
func (s ItemCSorter) Swap(i, j int)      { s[i], s[j] = s[j], s[i] }

func sortItems(items []Item) {
	sorter := ItemCSorter(items)
	sort.Sort(sorter)
}
Alternative implementation:
type ItemsSorter struct {
	items []Item
	c     func(x, y Item) bool
}

func (s ItemsSorter) Len() int           { return len(s.items) }
func (s ItemsSorter) Less(i, j int) bool { return s.c(s.items[i], s.items[j]) }
func (s ItemsSorter) Swap(i, j int)      { s.items[i], s.items[j] = s.items[j], s.items[i] }

func sortItems(items []Item, c func(x, y Item) bool) {
	sorter := ItemsSorter{
		items,
		c,
	}
	sort.Sort(sorter)
}
Alternative implementation:
sort.Slice(items, func(i, j int) bool {
	return c(items[i], items[j])
})
101
Make an HTTP request with method GET to URL u, then store the body of the response in string s.
res, err := http.Get(u)
if err != nil {
	return err
}
buffer, err := ioutil.ReadAll(res.Body)
res.Body.Close()
if err != nil {
	return err
}
s := string(buffer)
102
Make an HTTP request with method GET to URL u, then store the body of the response in file result.txt. Try to save the data as it arrives if possible, without having all its content in memory at once.
resp, err := http.Get(u)
if err != nil {
	return err
}
defer resp.Body.Close()
if resp.StatusCode != 200 {
	return fmt.Errorf("Status: %v", resp.Status)
}
out, err := os.Create("result.txt")
if err != nil {
	return err
}
defer out.Close()
_, err = io.Copy(out, resp.Body)
if err != nil {
	return err
}
103
Read from file data.xml and write its content into object x.
Assume the XML data is suitable for the type of x.
buffer, err := ioutil.ReadFile("data.xml")
if err != nil {
	return err
}
err = xml.Unmarshal(buffer, &x)
if err != nil {
	return err
}
104
Write content of object x into file data.xml.
buffer, err := xml.MarshalIndent(x, "", "  ")
if err != nil {
	return err
}
err = ioutil.WriteFile("data.xml", buffer, 0644)
105
Assign to string s the name of the currently executing program (but not its full path).
String s = System.getProperty("sun.java.command");
path := os.Args[0]
s = filepath.Base(path)
106
Assign to string dir the path of the working directory.
(This is not necessarily the folder containing the executable itself)
String path = this.getClass().getClassLoader().getResource("").getPath();
dir, err := os.Getwd()
107
Assign to string dir the path of the folder containing the currently running executable.
(This is not necessarily the working directory, though.)
programPath := os.Args[0]
absolutePath, err := filepath.Abs(programPath)
if err != nil {
	return err
}
dir := filepath.Dir(absolutePath)
109
Set n to the number of bytes of a variable t (of type T).
var t T
tType := reflect.TypeOf(t)
n := tType.Size()
110
Set boolean blank to true if string s is empty, or null, or contains only whitespace ; false otherwise.
boolean blank = StringUtils.isBlank(s);
Alternative implementation:
boolean blank = s==null || s.trim().isEmpty();
Alternative implementation:
boolean blank = s==null || s.isBlank();
blank := strings.TrimSpace(s) == ""
111
From current process, run program x with command-line parameters "a", "b".
err := exec.Command("x", "a", "b").Run()
112
Print each key k with its value x from an associative array mymap, in ascending order of k.
SortedMap<K, V> mymap = new TreeMap<>();
...
for(Map.Entry<K, V> e: mymap.entrySet())
	System.out.println("Key=" + e.getKey() + ", Value=" + e.getValue());
Alternative implementation:
List<K> keys = new ArrayList<>(mymap.keySet());
Collections.sort(keys);
for(K k: keys)
	System.out.println("Key=" + k + ", Value=" + mymap.get(k));
Alternative implementation:
var map = Map.of("a", 1, "d", 4, "c", 3, "b", 2);
new TreeMap<>(map).entrySet().forEach(System.out::println);
Alternative implementation:
mymap.entrySet().stream().sorted(Entry.comparingByKey()).forEach(System.out::println);
keys := make([]string, 0, len(mymap))
for k := range mymap {
	keys = append(keys, k)
}
sort.Strings(keys)

for _, k := range keys {
	x := mymap[k]
	fmt.Println("Key =", k, ", Value =", x)
}
113
Print each key k with its value x from an associative array mymap, in ascending order of x.
Note that multiple entries may exist for the same value x.
type entry struct {
	key   string
	value int
}

type entries []entry
func (list entries) Len() int { return len(list) }
func (list entries) Less(i, j int) bool { return list[i].value < list[j].value }
func (list entries) Swap(i, j int) { list[i], list[j] = list[j], list[i] }

entries := make(entries, 0, len(mymap))
for k, x := range mymap {
	entries = append(entries, entry{key: k, values: x})
}
sort.Sort(entries)

for _, e := range entries {
	fmt.Println("Key =", e.key, ", Value =", e.value)
}
Alternative implementation:
type entry struct {
	key   string
	value int
}

entries := make([]entry, 0, len(mymap))
for k, x := range mymap {
	entries = append(entries, entry{key: k, value: x})
}
sort.Slice(entries, func(i, j int) bool {
	return entries[i].value < entries[j].value
})

for _, e := range entries {
	fmt.Println("Key =", e.key, ", Value =", e.value)
}
114
Set boolean b to true if objects x and y contain the same values, recursively comparing all referenced elements in x and y.
Tell if the code correctly handles recursive types.
b := reflect.DeepEqual(x, y)
115
Set boolean b to true if date d1 is strictly before date d2 ; false otherwise.
boolean before = (d1.compareTo(d2) == -1);
b := d1.Before(d2)
116
Remove all occurrences of string w from string s1, and store the result in s2.
String s2 = s1.replace(w, "");
s2 := strings.Replace(s1, w, "", -1)
117
Set n to the number of elements of list x.
int n = x.size();
Alternative implementation:
int n = x.length;
n := len(x)
118
Create set y from list x.
x may contain duplicates. y is unordered and has no repeated values.
Set<T> y = new HashSet<>(x);
Alternative implementation:
Set<T> y = new HashSet<T>(x);
y := make(map[T]struct{}, len(x))
for _, v := range x {
	y[v] = struct{}{}
}
119
Remove duplicates from list x.
Explain if original order is preserved.
Set<T> uniques = new HashSet<>(x);
x.clear();
x.addAll(uniques);
Alternative implementation:
x = new ArrayList<T>(new HashSet<T>(x));
Alternative implementation:
final HashSet<T> seen = new HashSet<T>();
final Iterator<T> listIt = x.iterator();
while (listIt.hasNext()) {
  final T curr = listIt.next();
  if (seen.contains(curr)) {
    listIt.remove();
  } else {
    seen.add(curr);
  }
}
y := make(map[T]struct{}, len(x))
for _, v := range x {
	y[v] = struct{}{}
}
x2 := make([]T, 0, len(y))
for _, v := range x {
	if _, ok := y[v]; ok {
		x2 = append(x2, v)
		delete(y, v)
	}
}
x = x2
Alternative implementation:
seen := make(map[T]bool)
j := 0
for _, v := range x {
	if !seen[v] {
		x[j] = v
		j++
		seen[v] = true
	}
}
x = x[:j]
Alternative implementation:
seen := make(map[T]bool)
j := 0
for _, v := range x {
	if !seen[v] {
		x[j] = v
		j++
		seen[v] = true
	}
}
for i := j; i < len(x); i++ {
	x[i] = nil
}
x = x[:j]
120
Read an integer value from the standard input into variable n
Scanner in = new Scanner(System.in);
n = in.nextInt();
_, err := fmt.Scan(&n)
Alternative implementation:
_, err := fmt.Scanf("%d", &n)
121
Listen UDP traffic on port p and read 1024 bytes into buffer b.
int len = 1024;
int p = 8888;
byte[] b = new byte[len];
try (DatagramSocket socket = new DatagramSocket(p)) {
  DatagramPacket packet = new DatagramPacket(b, len);
  socket.receive(packet);
}
ServerAddr,err := net.ResolveUDPAddr("udp",p)
if err != nil {
	return err
}
ServerConn, err := net.ListenUDP("udp", ServerAddr)
if err != nil {
	return err
}
defer ServerConn.Close()
n,addr,err := ServerConn.ReadFromUDP(b[:1024])
if err != nil {
	return err
}
if n<1024 {
	return fmt.Errorf("Only %d bytes could be read.", n)
}
122
Create an enumerated type Suit with 4 possible values SPADES, HEARTS, DIAMONDS, CLUBS.
enum Suit{
  SPADES,
  HEARTS,
  DIAMONDS,
  CLUBS;
}
type Suit int

const (
  Spades Suit = iota
  Hearts
  Diamonds
  Clubs
)
123
Verify that predicate isConsistent returns true, otherwise report assertion violation.
Explain if the assertion is executed even in production environment or not.
assert isConsistent() : "State consistency violated";
if !isConsistent() {
	panic("State consistency violated")
}
124
Write function binarySearch which returns the index of an element having value x in sorted array a, or -1 if no such element.
static int binarySearch(final int[] arr, final int key) {
    final int index = Arrays.binarySearch(arr, key);
    return index < 0 ? - 1 : index;
}
func binarySearch(a []T, x T) int {
	imin, imax := 0, len(a)-1
	for imin <= imax {
		imid := (imin + imax) / 2
		switch {
		case a[imid] == x:
			return imid
		case a[imid] < x:
			imin = imid + 1
		default:
			imax = imid - 1
		}
	}
	return -1
}
Alternative implementation:
func binarySearch(a []int, x int) int {
	i := sort.SearchInts(a, x)
	if i < len(a) && a[i] == x {
		return i
	}
	return -1
}
Alternative implementation:
func binarySearch(a []T, x T) int {
	f := func(i int) bool { return a[i] >= x }
	i := sort.Search(len(a), f)
	if i < len(a) && a[i] == x {
		return i
	}
	return -1
}
125
measure the duration t, in nano seconds, of a call to the function foo. Print this duration.
t1 := time.Now()
foo()
t := time.Since(t1)
ns := int64(t / time.Nanosecond)
fmt.Printf("%dns\n", ns)
Alternative implementation:
t1 := time.Now()
foo()
t := time.Since(t1)
ns := t.Nanoseconds()
fmt.Printf("%dns\n", ns)
126
Write a function foo that returns a string and a boolean value.
static Object[] returnAnything() {
    return new Object[]{"a string", true};
}

public static void main (String[] args) {
    Object[] array = returnAnything();
    System.out.println(array[0]);
    System.out.println(array[1]);
}
func foo() (string, bool) {
	return "Too good to be", true
}
128
Call a function f on every node of a tree, in breadth-first prefix order
static void breadthFirstSearch(Node root, Consumer<Node> f) {
    Queue<Node> queue = new LinkedList<>();
    queue.offer(root);

    while(!queue.isEmpty()) {
        Node polled = queue.poll();
        f.accept(polled);
        polled.children.forEach(a -> queue.offer(a));
    }
}
     
func (root *Tree) Bfs(f func(*Tree)) {
	if root == nil {
		return
	}
	queue := []*Tree{root}
	for len(queue) > 0 {
		t := queue[0]
		queue = queue[1:]
		f(t)
		queue = append(queue, t.Children...)
	}
}
129
Call a function f on every vertex accessible from vertex start, in breadth-first prefix order
func (start *Vertex) Bfs(f func(*Vertex)) {
	queue := []*Vertex{start}
	seen := map[*Vertex]bool{start: true}
	for len(queue) > 0 {
		v := queue[0]
		queue = queue[1:]
		f(v)
		for next, isEdge := range v.Neighbours {
			if isEdge && !seen[next] {
				queue = append(queue, next)
				seen[next] = true
			}
		}
	}
}
130
Call a function f on every vertex accessible for vertex v, in depth-first prefix order
func (v *Vertex) Dfs(f func(*Vertex), seen map[*Vertex]bool) {
	seen[v] = true
	f(v)
	for next, isEdge := range v.Neighbours {
		if isEdge && !seen[next] {
			next.Dfs(f, seen)
		}
	}
}
131
Execute f1 if condition c1 is true, or else f2 if condition c2 is true, or else f3 if condition c3 is true.
Don't evaluate a condition when a previous condition was true.
if (c1) {
   f1();
} else if (c2) {
   f2();
} else if (c3) { 
   f3();
}
switch {
case c1:
	f1()
case c2:
	f2()
case c3:
	f3()
}
132
Run procedure f, and return the duration of the execution of f.
long clock(Runnable f) {
    long t0 = System.currentTimeMillis();
    f.run();
    long t1 = System.currentTimeMillis();
    return t1 - t0;
}
func clock(f func()) time.Duration {
	t := time.Now()
	f()
	return time.Since(t)
}
133
Set boolean ok to true if string word is contained in string s as a substring, even if the case doesn't match, or to false otherwise.
ok = s.toLowerCase().contains(word.toLowerCase());
lowerS, lowerWord := strings.ToLower(s), strings.ToLower(word)
ok := strings.Contains(lowerS, lowerWord)
134
Declare and initialize a new list items, containing 3 elements a, b, c.
List<T> items = new ArrayList<>();
items.add(a);
items.add(b);
items.add(c);
Alternative implementation:
List<T> items = Arrays.asList(a, b, c);
Alternative implementation:
var items = List.of(a, b, c);
items := []T{a, b, c}
135
Remove at most 1 item from list items, having value x.
This will alter the original list or return a new list, depending on which is more idiomatic.
If there are several occurrences of x in items, remove only one of them. If x is absent, keep items unchanged.
items.stream().findFirst().filter(item -> "x".equals(item)).ifPresent(removeIndex -> items.remove(removeIndex));
for i, y := range items {
	if y == x {
		items = append(items[:i], items[i+1:]...)
		break
	}
}
Alternative implementation:
for i, y := range items {
	if y == x {
		copy(items[i:], items[i+1:])
		items[len(items)-1] = nil
		items = items[:len(items)-1]
		break
	}
}
136
Remove all occurrences of value x from list items.
This will alter the original list or return a new list, depending on which is more idiomatic.
items.removeAll(Collections.singleton(x));
items2 := make([]T, 0, len(items))
for _, v := range items {
	if v != x {
		items2 = append(items2, v)
	}
}
Alternative implementation:
j := 0
for i, v := range items {
	if v != x {
		items[j] = items[i]
		j++
	}
}
items = items[:j]
Alternative implementation:
j := 0
for i, v := range items {
	if v != x {
		items[j] = items[i]
		j++
	}
}
for k := j; k < len(items); k++ {
	items[k] = nil
}
items = items[:j]
137
Set boolean b to true if string s contains only characters in range '0'..'9', false otherwise.
boolean b = s.matches("[0-9]*");
b := true
for _, c := range s {
	if c < '0' || c > '9' {
		b = false
		break
	}
}
Alternative implementation:
isNotDigit := func(c rune) bool { return c < '0' || c > '9' }
b := strings.IndexFunc(s, isNotDigit) == -1
138
Create a new temporary file on filesystem.
tmpfile, err := ioutil.TempFile("", "")
139
Create a new temporary folder on filesystem, for writing.
dir, err := ioutil.TempDir("", "")
140
Delete from map m the entry having key k.

Explain what happens if k is not an existing key in m.
map.remove(k);
delete(m, k)
141
Iterate in sequence over the elements of the list items1 then items2. For each iteration print the element.
items1.forEach(System.out::println);
items2.forEach(System.out::println);
Alternative implementation:
for (String item : items1) {
	System.out.println(item);
}
for (String item : items2) {
	System.out.println(item);
}
Alternative implementation:
Stream.concat(
	items1.stream(), 
	items2.stream()
).forEach(System.out::println);
for _, v := range items1 {
	fmt.Println(v)
}
for _, v := range items2 {
	fmt.Println(v)
}
142
Assign to string s the hexadecimal representation (base 16) of integer x.

E.g. 999 -> "3e7"
String s = Integer.toHexString(x);
s := strconv.FormatInt(x, 16)
Alternative implementation:
s := fmt.Sprintf("%x", x)
143
Iterate alternatively over the elements of the list items1 and items2. For each iteration, print the element.

Explain what happens if items1 and items2 have different size.
Iterator<String> iter1 = items1.iterator();
Iterator<String> iter2 = items2.iterator();
while (iter1.hasNext() || iter2.hasNext()) {
	if (iter1.hasNext()) {
		System.out.println(iter1.next());
	}
	if (iter2.hasNext()) {
		System.out.println(iter2.next());
	}
}
Alternative implementation:
IntStream.range(0, Math.max(items1.size(), items2.size()))
	.boxed()
	.flatMap(idx -> Stream.of(
		items1.size() > idx ? items1.get(idx) : null,
		items2.size() > idx ? items2.get(idx) : null
	))
	.filter(Objects::nonNull)
	.forEach(System.out::println);
for i := 0; i < len(items1) || i < len(items2); i++ {
	if i < len(items1) {
		fmt.Println(items1[i])
	}
	if i < len(items2) {
		fmt.Println(items2[i])
	}
}
144
Set boolean b to true if file at path fp exists on filesystem; false otherwise.

Beware that you should never do this and then in the next instruction assume the result is still valid, this is a race condition on any multitasking OS.
boolean b = new File(fb).exists();
_, err := os.Stat(fp)
b := !os.IsNotExist(err)
145
Print message msg, prepended by current date and time.

Explain what behavior is idiomatic: to stdout or stderr, and what the date format is.
Logger LOGGER = Logger.getLogger(MyClass.class.getName());

LOGGER.info(msg);
log.Println(msg)
146
Extract floating point value f from its string representation s
String floatString = "14.5";
float x = Float.parseFloat(floatString);
double y = Double.parseFloat(floatString);
f, err := strconv.ParseFloat(s, 64)
147
Create string t from string s, keeping only ASCII characters
String t = s.replaceAll("[^\\x00-\\x7F]", "");
re := regexp.MustCompile("[[:^ascii:]]")
t := re.ReplaceAllLiteralString(s, "")
Alternative implementation:
t := strings.Map(func(r rune) rune {
	if r > unicode.MaxASCII {
		return -1
	}
	return r
}, s)
148
Read a list of integer numbers from the standard input, until EOF.
var ints []int
s := bufio.NewScanner(os.Stdin)
s.Split(bufio.ScanWords)
for s.Scan() {
	i, err := strconv.Atoi(s.Text())
	if err == nil {
		ints = append(ints, i)
	}
}
if err := s.Err(); err != nil {
	return err
}
149
As an exception, this content is not under license CC BY-SA 3.0 like the rest of this website.
 
 
150
Remove last character from string p, if this character is a slash /.
if (p.endsWith("/")) {
    p = p.substring(0, p.length() - 1);
}
Alternative implementation:
p = p.replaceAll("/$", "");
p = strings.TrimSuffix(p, "/")
151
Remove last character from string p, if this character is the file path separator of current platform.

Note that this also transforms unix root path "/" into the empty string!
sep := fmt.Sprintf("%c", os.PathSeparator)
p = strings.TrimSuffix(p, sep)
Alternative implementation:
sep := fmt.Sprintf("%c", filepath.Separator)
p = strings.TrimSuffix(p, sep)
152
Create string s containing only the character c.
String s = String.valueOf(c);
Alternative implementation:
String s = Character.toString(c);
Alternative implementation:
String s = c + "";
Alternative implementation:
String s = = new Character(c).toString();
s := fmt.Sprintf("%c", c)
153
Create string t as the concatenation of string s and integer i.
String t = s + i;
t := fmt.Sprintf("%s%d", s, i)
154
Find color c, the average between colors c1, c2.

c, c1, c2 are strings of hex color codes: 7 chars, beginning with a number sign # .
Assume linear computations, ignore gamma corrections.
String r1 = c1.substring(1,3);
String g1 = c1.substring(3,5);
String b1 = c1.substring(5,7);

String r2 = c2.substring(1,3);
String g2 = c2.substring(3,5);
String b2 = c2.substring(5,7);

String r = String.format("%02X", (Integer.parseInt(r1, 16)+Integer.parseInt(r2, 16))/2 );
String g = String.format("%02X", (Integer.parseInt(g1, 16)+Integer.parseInt(g2, 16))/2 );
String b = String.format("%02X", (Integer.parseInt(b1, 16)+Integer.parseInt(b2, 16))/2 );

String c = "#" + r + g + b;
Alternative implementation:
StringBuilder sb = new StringBuilder("#");
for(int i=0;i<3;i++) {
  String sub1 = c1.substring(1+2*i,3+2*i);
  String sub2 = c2.substring(1+2*i,3+2*i);
  int v1 = Integer.parseInt(sub1, 16);
  int v2 = Integer.parseInt(sub2, 16);
  int v = (v1 + v2)/2;
  String sub = String.format("%02X", v);
  sb.append(sub);
}
String c = sb.toString();
r1, _ := strconv.ParseInt(c1[1:3], 16, 0)
r2, _ := strconv.ParseInt(c2[1:3], 16, 0)
r := (r1 + r2) / 2

g1, _ := strconv.ParseInt(c1[3:5], 16, 0)
g2, _ := strconv.ParseInt(c2[3:5], 16, 0)
g := (g1 + g2) / 2

b1, _ := strconv.ParseInt(c1[5:7], 16, 0)
b2, _ := strconv.ParseInt(c2[5:7], 16, 0)
b := (b1 + b2) / 2

c := fmt.Sprintf("#%02X%02X%02X", r, g, b)
Alternative implementation:
var buf [7]byte
buf[0] = '#'
for i := 0; i < 3; i++ {
	sub1 := c1[1+2*i : 3+2*i]
	sub2 := c2[1+2*i : 3+2*i]
	v1, _ := strconv.ParseInt(sub1, 16, 0)
	v2, _ := strconv.ParseInt(sub2, 16, 0)
	v := (v1 + v2) / 2
	sub := fmt.Sprintf("%02X", v)
	copy(buf[1+2*i:3+2*i], sub)
}
c := string(buf[:])
155
Delete from filesystem the file having path filepath.
new File(filepath).delete();
err := os.Remove(filepath)
156
Assign to string s the value of integer i in 3 decimal digits. Pad with zeros if i < 100. Keep all digits if i1000.
String s = String.format("%03d", i);
s := fmt.Sprintf("%03d", i)
157
Initialize a constant planet with string value "Earth".
static final String planet = "Earth";
const planet = "Earth"
158
Create a new list y from randomly picking exactly k elements from list x.

It is assumed that x has at least k elements.
Each element must have same probability to be picked.
Each element from x must be picked at most once.
Explain if the original ordering is preserved or not.
y := make([]T, k)
perm := rand.Perm(len(x))
for i, v := range perm[:k] {
	y[i] = x[v]
}
159
Define a Trie data structure, where entries have an associated value.
(Not all nodes are entries)
type Trie struct {
	c        rune
	children map[rune]*Trie
	isEntry  bool
	value    V
}
160
Execute f32() if platform is 32-bit, or f64() if platform is 64-bit.
This can be either a compile-time condition (depending on target) or a runtime detection.
switch(System.getProperty("sun.arch.data.model")) {
  case "64": 
    f64(); 
    break;
  case "32":
    f32();
    break;
}
if strconv.IntSize==32 {
	f32()
}
if strconv.IntSize==64 {
	f64()
}
161
Multiply all the elements of the list elements by a constant c
elements.stream().map(e -> e*c).collect(Collectors.toList())
for i := range elements {
	elements[i] *= c
}
162
execute bat if b is a program option and fox if f is a program option.
var b = flag.Bool("b", false, "Do bat")
var f = flag.Bool("f", false, "Do fox")

func main() {
	flag.Parse()
	if *b {
		bar()
	}
	if *f {
		fox()
	}
}
163
Print all the list elements, two by two, assuming list length is even.
for(int i = 0; i < list.length; i += 2) {
  System.out.println(list[i] + ", " + list[i + 1]);
}
for i := 0; i+1 < len(list); i += 2 {
	fmt.Println(list[i], list[i+1])
}
164
Open the URL s in the default browser.
Set boolean b to indicate whether the operation was successful.
b := open.Start(s) == nil
Alternative implementation:
func openbrowser(url string) {
	var err error

	switch runtime.GOOS {
	case "linux":
		err = exec.Command("xdg-open", url).Start()
	case "windows":
		err = exec.Command("rundll32", "url.dll,FileProtocolHandler", url).Start()
	case "darwin":
		err = exec.Command("open", url).Start()
	default:
		err = fmt.Errorf("unsupported platform")
	}
	if err != nil {
		log.Fatal(err)
	}

}
165
Assign to variable x the last element of list items.
int x = items[items.length - 1];
x := items[len(items)-1]
166
Create list ab containing all the elements of list a, followed by all elements of list b.
var ab = new ArrayList<>(a);
ab.addAll(b);
ab := append(a, b...)
Alternative implementation:
var ab []T
ab = append(append(ab, a...), b...)
Alternative implementation:
ab := make([]T, len(a)+len(b))
copy(ab, a)
copy(ab[len(a):], b)
167
Create string t consisting of string s with its prefix p removed (if s starts with p).
String t = s.replaceFirst("^" + p, "");
t := strings.TrimPrefix(s, p)
168
Create string t consisting of string s with its suffix w removed (if s ends with w).
t := strings.TrimSuffix(s, w)
169
Assign to integer n the number of characters of string s.
Make sure that multibyte characters are properly handled.
n can be different from the number of bytes of s.
int n = s.length();
n := utf8.RuneCountInString(s)
170
Set n to the number of elements stored in mymap.

This is not always equal to the map capacity.
int n = mymap.size();
n := len(mymap)
171
Append element x to the list s.
List<String> stringList = new ArrayList<>();
stringList.add("hello")
s = append(s, x)
172
Insert value v for key k in map m.
m.put(k, v);
m[k] = v
173
Number will be formatted with a comma separator between every group of thousands.
String.format("%,d", 1000000);
p := message.NewPrinter(language.English)
s := p.Sprintf("%d\n", 1000)
Alternative implementation:
n := strconv.Itoa(23489)
s := thousands.Separate(n, "en")
174
Make a HTTP request with method POST to URL u
response, err := http.Post(u, contentType, body)
Alternative implementation:
response, err := http.PostForm(u, formValues)
175
From array a of n bytes, build the equivalent hex string s of 2n digits.
Each byte (256 possible values) is encoded as two hexadecimal characters (16 possible values per digit).
s := hex.EncodeToString(a)
176
From hex string s of 2n digits, build the equivalent array a of n bytes.
Each pair of hexadecimal characters (16 possible values per digit) is decoded into one byte (256 possible values).
a, err := hex.DecodeString(s)
if err != nil {
	log.Fatal(err)
}
177
Construct a list L that contains all filenames that have the extension ".jpg" , ".jpeg" or ".png" in directory D and all it's subdirectories.
L := []string{}
err := filepath.Walk(D, func(path string, info os.FileInfo, err error) error {
	if err != nil {
		fmt.Printf("failure accessing a path %q: %v\n", path, err)
		return err
	}
	for _, ext := range []string{".jpg", ".jpeg", ".png"} {
		if strings.HasSuffix(path, ext) {
			L = append(L, path)
			break
		}
	}
	return nil
})
178
Set boolean b to true if if the point with coordinates (x,y) is inside the rectangle with coordinates (x1,y1,x2,y2) , or to false otherwise.
Describe if the edges are considered to be inside the rectangle.
p := image.Pt(x, y)
r := image.Rect(x1, y1, x2, y2)
b := p.In(r)
179
Return the center c of the rectangle with coördinates(x1,y1,x2,y2)