自动装箱与拆箱

 1 public static void main(String[] args) {
 2         Integer a = 1;
 3         Integer b = 2;
 4         Integer c = 3;
 5         Integer d = 3;
 6         Integer e = 321;
 7         Integer f = 321;
 8         Long g = 3L;
 9         System.out.println(c == d);
10         System.out.println(e == f);
11         System.out.println(c == (a+b));
12         System.out.println(c.equals(a+b));
13         System.out.println(g == (a+b));
14         System.out.println(g.equals(a+b));
15     }