【java】Interger 比较相等与否

public static void main(String[] args) {
        Integer a=100,b=100,c=600,d=600;
        boolean equals1 = a.equals(b);
        boolean equals2 = c.equals(d);
        boolean equals3 = false;
        boolean equals4 = false;
        if(a==b){
            equals3=true;
        }
        if(c==d){
            equals4=true;
        }
        System.out.println(equals1);
        System.out.println(equals2);
        System.out.println(equals3);
        System.out.println(equals4);
    }