（面试题）关于Integer的比较以及==和equals的区别

**先上段代码

public class Test03 {

    public static void main(String[] args) {
        Integer f1 = 100, f2 = 100, f3 = 150, f4 = 150;

        System.out.println(f1 == f2);//返回true
        System.out.println(f1.equals(f2));//返回true

        System.out.println(f3 == f4);//返回false
        System.out.println(f3.equals(f4));//返回true
    }
}

public class Test03 {

    public