自动装箱的陷阱

 1 class TestAuto{
 2     public static void main(String[] args){
 3         int i = 1;
 4         Integer a = 1;
 5         Integer b = 2;
 6         Integer c = 3;
 7         Integer d = 3;
 8         Integer e = 321;
 9         Integer f = 321;
10         Long g = 3L;
11         System.out.println(i == a);//true
12         System.out.println(c == d);//true
13         System.out.println(e == f);//false
14         System.out.println(c == (a + b));//true
15         System.out.println(c.equals(a + b));//true
16         System.out.println(g == (a + b));//true
17         System.out.println(g.equals(a + b));//false
18     }
19 }