check if a number is integer or not in java

/**
 * @author lautturi.com
 * Java example: check if a number is of type integer
 */

import java.util.*;

public class Lautturi {

	public static void main(String[] args) throws ParseException {
		
		int x = 123;
		if (x == (int)x)
		{
		   // Number is integer
			System.out.println("x is a integer");
		}
		double y = 123.0;
		if (y == (int)y)
		{
		   // Number is integer
			System.out.println("y is a integer");
		}

		double d = 123.5;
		if (d == (int)d)
		{
		   // Number is integer
			System.out.println("d is a integer");
		}
		String z = "123";
		if (z == (int)z) // Comile Error : Cannot cast from String to int
		{
		   // Number is integer
			System.out.println("z is a integer");
		}
		
	}
}

output:

x is a integer
y is a integer