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Programming-Idioms

  • Ruby
  • Java

Idiom #89 Handle invalid argument

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);

IllegalArgumentException is a RuntimeException, thus it needn't be declared in the function signature.
Other standard exceptions cover possible cases: NullPointerException, etc.
It is the caller's responsibility to provide valid input, or catch the possible exceptions.
<T> void f(T x) throws Exception {
    if (x != value) throw new Exception();
}
<T> void f(T x) {
    Objects.requireNonNull(x);
}
void f(int x) {
    Objects.checkIndex(x, 123);
}
raise ArgumentError, "invalid value #{x}."

The error-message will automatically be enriched with filename, methodname and linenumber.
enum {
    E_OK,
    E_OUT_OF_RANGE
};

int square(int x, int *result) {
    if (x > 1073741823) {
        return E_OUT_OF_RANGE;
    }
    *result = x*x;
    return E_OK;
}
New implementation...
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programming-idioms.org 
throw new IllegalArgumentException("Invalid value for x:" + x);
<T> void f(T x) throws Exception {
    if (x != value) throw new Exception();
}
<T> void f(T x) {
    Objects.requireNonNull(x);
}
void f(int x) {
    Objects.checkIndex(x, 123);
}
raise ArgumentError, "invalid value #{x}."
enum {
    E_OK,
    E_OUT_OF_RANGE
};

int square(int x, int *result) {
    if (x > 1073741823) {
        return E_OUT_OF_RANGE;
    }
    *result = x*x;
    return E_OK;
}
throw domain_error("oops!");
throw new ArgumentException(nameof(×));
throw new Exception("invalid value for x (%s) in '%s'".format(x, __PRETTY_FUNCTION__));
void foo(int x)
in
{
    assert(x != 0, "wrong value for x");
}
body
{
    // function
}
error(badarg).
  if (x > largest_value) error stop "Illegal value in function."
return nil, fmt.Errorf("invalid value for x: %v", x)
throw new IllegalArgumentException("Invalid value for x: $x")
sqrt' :: Int -> Either String Int
sqrt' x | x < 0 = Left "Invalid argument"
sqrt' x         = Right (sqrt x)
throw new Error('x is invalid');
return nil, "Invalid argument x"
error("Invalid argument x")
throw new \InvalidArgumentException($x . ' is invalid.');
Raise EInvalidArgument.CreatFmt('Invalid value: %d',[x]);
die "Invalid argument $x";
raise ValueError("x is invalid")
enum CustomError { InvalidAnswer }

fn do_stuff(x: i32) -> Result<i32, CustomError> {
    if x != 42 {
        Err(CustomError::InvalidAnswer)
    } else {
        Ok(x)
    }
}