/* package whatever; // don't place package name! */
 
import java.util.*;
import java.util.function.*;
import java.lang.*;
import java.io.*;
 
/* Name of the class has to be "Main" only if the class is public. */
class Ideone
{
 
	@FunctionalInterface
    interface UnaryOperator<T> extends Function<T, T> {
        static UnaryOperator<Object> IDENTITY_FUNCTION = (k -> k);
        static <T> UnaryOperator<T> identity() {
            return (UnaryOperator)IDENTITY_FUNCTION;
        }
    }
 
	public static void main (String[] args) throws java.lang.Exception
	{
		UnaryOperator<String> sameString = UnaryOperator.identity();
		UnaryOperator<Integer> sameInt = UnaryOperator.identity();
		System.out.println(sameString.apply("hello, world!"));
		System.out.println(sameInt.apply(123));
	}
}
 

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