1 package cn.itcast.p2.wrapper.demo;
2
3 public class WrapperDemo2 {
4
5 public static void main(String[] args) {
6 // TODO Auto-generated method stub
7 int num = 4;
8 num = num + 5;
9 Integer i = 4;//i = new Integer(4);自动装箱(简化书写)
10 i = i + 6;//i = new Integer(i.intValue()+6); //i.intValue()自动拆箱
11 //Integer i = null 引用数据类型多了个空**
12 //i = i + 6 拆箱会出现异常 自动装箱和拆箱要进行间断性操作
13 show(55);
14
15 Integer a = new Integer(127);
16 Integer b = new Integer(127);
17 System.out.println(a==b);//false
18 System.out.println(a.equals(b));//true
19 Integer xInteger = 127; //true //jdk1.5以后，自动装箱，如果装箱的是一个字节，那么该数据会被共享不会重新开辟空间
20 Integer yInteger = 127;//true
21 Integer xInteger2 = 128;//false //装箱超过一个字节，重新开辟空间
22 Integer yInteger2 = 128;//true
23 System.out.println(xInteger==yInteger);
24 System.out.println(xInteger.equals(yInteger));
25
26 }
27 public static void show(Object a) {//Object a = new Integer(55)
28 System.out.println("a="+a);
29 }
30
31 }
