What is the identity method of the Function interface in Java?

identity is a static method of the Function interface that always returns the input argument.

Syntax

static <T> Function<T, T> identity()

Parameters

The method has no parameters.

Return value

The method returns a function that always returns its input argument.

Code

import java.util.function.Function;
public class Main {
    public static void main(String[] args){
        Function<Integer, Integer> identity = Function.identity();
        int arg = 1;
        System.out.printf("(%s == identity.apply(%s)) = %s", arg, arg, (arg == identity.apply(arg)));
    }
}

Explanation

  • Line 1 - We import the Function interface.
  • Line 6 - We define an identity function using the identity() method.
  • Line 7 - We define an integer called arg.
  • Line 8 - We check whether arg and the value returned are equal. We do this by using the apply() method passing arg as an argument are equal.

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