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Idiom #22 Convert string to integer

Extract the integer value i from its string representation s (in radix 10)

Turning the string \"123\" into the integer value 123 
Integer i = s.toInteger()

While all the Java examples work in Groovy, too, you can also use the toInteger() method that Groovy adds to all CharSequences. It throws a NumberFormatException if the string is not a number.
const i = +s
let i = parseInt(s, 10)

parseInt(string, radix);
The radix is an integer between 2 and 36.
const i = Number(s);
val i = s.toIntOrNull()

i is null if s can not be converted to an integer
val i = s.toInt()
let i = s.parse::<i32>().unwrap();

This panics if s is not a valid number.
s is parsed to 32-bits signed integer here (change number type if needed).
let i: i32 = s.parse().unwrap_or(0);

This explicitly sets the value to 0 if it can't be parsed to an integer.
let i = match s.parse::<i32>() {
  Ok(i) => i,
  Err(_e) => -1,
};

s is parsed to 32-bits signed integer here (change number type if needed).
-1 is used here as a fallback value, but any error handling instructions can be used.
int i = Integer.parseInt(s);

Throws NumberFormatException if s does not contain a parsable integer
int i = new Integer(s).intValue();

Throws NumberFormatException if s does not contain a parsable integer
int i = s.chars()
     .map(x -> x - '0')
     .reduce((a, b) -> (a * 10) + b)
     .getAsInt();
Integer i = Integer.valueOf(s, 10);

The second argument in the valueOf method denotes the radix (or base)
i = int(s)
I : Integer := Integer'Value (s);
New implementation...
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programming-idioms.org 
Integer i = s.toInteger()
const i = +s
let i = parseInt(s, 10)
const i = Number(s);
val i = s.toIntOrNull()
val i = s.toInt()
let i = s.parse::<i32>().unwrap();
let i: i32 = s.parse().unwrap_or(0);
let i = match s.parse::<i32>() {
  Ok(i) => i,
  Err(_e) => -1,
};
int i = Integer.parseInt(s);
int i = new Integer(s).intValue();
int i = s.chars()
     .map(x -> x - '0')
     .reduce((a, b) -> (a * 10) + b)
     .getAsInt();
Integer i = Integer.valueOf(s, 10);
i = int(s)
I : Integer := Integer'Value (s);
int i = atoi(s);
i = (int)strtol(s, (char **)NULL, 10);
(def i (Integer. s))
(def i (Integer/parseInt s))
std::string s("123");
int i;
std::from_chars(s.data(), s.data() + s.size(), i, 10);
std::stringstream ss(str);
int i;
ss >> i;
int i = std::atoi(s);
int i = std::stoi(s);
long i = Convert.ToInt64(s);
int i = int.Parse(s);
auto i = s.to!int;
var i = int.parse(s);
i = String.to_integer(s)
I = list_to_integer(S).
read (unit=s,fmt=*) i
i, err := strconv.ParseInt(s, 10, 0)
i, err  := strconv.Atoi(s) 
let i = read s :: Integer
(setf i (parse-integer s))
i = tonumber(s)
int i=s.intValue
$i = intval($s, 10);
i := StrToInt(S);
my $i = $s + 0;

i = s.to_i
s.toInt
(define i (string->number s))
i := s asInteger.
Dim myint As Integer = CInt(("123"))