关于Integer比较问题

public class Test {
    public static void main(String[] args) {
        Integer a=127;
        Integer b=127;
        System.out.println(a==b);
        System.out.println(a.equals(b));
        Integer c=128;
        Integer d=128;
        System.out.println(c==d);
        System.out.println(c.equals(d));
        Integer e=0;
        Integer f=null;
        System.out.println(e==f);
        System.out.println(e.equals(f));
    }
}