i++和++i的作用和区别

package constxiong.interview;

/**
 * 测试 ++i 和 i++
 * @author ConstXiong
 * @date 2019-10-17 13:44:05
 */
public class TestAdd {

    public static void main(String[] args) {
        int a = 3;
        int b = a++;
        System.out.println("a=" + a);
        System.out.println("b=" + b);
        
        int x = 3;
        int y = ++x;
        System.out.println("x=" + x);
        System.out.println("y=" + y);
    }
    
}

a=4
b=3
x=4
y=4