本章提到的關於==的部分，一個完整的實驗如下：

 1 class Test {    
 2     public static void main(String[] args) {
 3         Integer i = new Integer(47);
 4         Integer j = new Integer(47);
 5         Integer i1 = 47;
 6         Integer j1 = 47;
 7         int i2 = new Integer(47);
 8         int j2 = new Integer(47);
 
 9         int i3 = 47;
10         int j3 = 47;
11         
12         System.out.println( i == j ); //false
13         System.out.println( i1 == j1 ); //true
14         System.out.println( i2 == j2 ); //true
15         System.out.println( i3 == j3 ); //true
16         System.out.println( i1 == j2 ); //true
17
 
         System.out.println( i1 == j3 ); //true
18         System.out.println( i2 == j3 ); //true
19         
20         String s = new String("java");
21         String s1 = new String("java");
22         String s2 = "java";
23         String s3 = "java";
24         System.out.println( s == s1 ); //false
 
25         System.out.println( s2 == s3 ); //true
26     }
27 }

Java編程思想讀書筆記_第三章