java.lang中String"="和"equals()"函数解析

　　java.lang是java语言的基础包。String类为lang包中的一个基础类。本文主要讨论 "="和"equals()"方法对String的不同判断结果。

"=" .VS. "equals()" :

　　"="判断的是两个String类型的引用是否指向同一个对象，如果是，那么表达式结果为true，如果不是，那么表达式结果为false;

　　"equals"判断的是两个String类型的引用所指向对象的值，如果相等，那么返回结果为true，如果不相等，那么返回结果为false;

下面是我的一段简单的实验程序。

 1 package BasicKnowledge.Testlang;
 2 
 3 public class StringTest {
 4     public static void main(String args[])
 5     {
 6         String str1;
 7         str1 = new String("Str");
 8         String str2 = new String("Str");
 9         
10         
11         
12         String str3;
13         str3 = str1;
14         String equal = "The two strings are equal with";
15         String notEqual = "The two strings are not equal";
16         
17         String stat2 = "str1 and str2 are two different objects but they have the same value";
18         if(equalSign(str1,str2))
19         {
20             System.out.println(stat2+";"+equal+" '=' sign");
21         }else System.out.println(stat2+";"+notEqual+" '=' sign");
22         
23         if(equalFunction(str1,str2))
24         {
25             System.out.println(stat2+";"+equal+ " 'equal()' function");
26         }else System.out.println(stat2+";"+notEqual+" 'equal()' fuction");
27         
28         str3 = str1;
29         String stat = "str3 shares the same reference with str1";
30         
31         if(equalSign(str1,str3))
32         {
33             System.out.println(stat+";"+equal+" '=' sign");
34         }else System.out.println(stat+";"+notEqual+" '=' sign");
35         
36         if(equalFunction(str1,str3))
37         {
38             System.out.println(stat+";"+equal+ " 'equal()' function");
39         }else System.out.println(stat+";"+notEqual+" 'equal()' fuction");
40     }
41     
42     static  boolean equalSign(String a, String b)//在静态方法中,是不能访问非静态成员,所以这里用static来形容
43     {
44         boolean backValue = true;
45         if(a == b)
46         {
47             backValue = true;
48         }else backValue = false;
49         return backValue;
50     }
51     
52     static  boolean equalFunction(String a, String b)
53     {
54         boolean backValue = true;
55         if(a.equals(b))
56         {
57             backValue = true;
58         }else backValue = false;
59         return backValue;
60     }
61 
62 }

编译和运行结果如下：

str1 and str2 are two different objects but they have the same value;The two strings are not equal '=' sign
str1 and str2 are two different objects but they have the same value;The two strings are equal with 'equal()' function
str3 shares the same reference with str1;The two strings are equal with '=' sign
str3 shares the same reference with str1;The two strings are equal with 'equal()' function

 

posted @ 2014-04-17 14:00  马七风  阅读(624)  评论(0)  编辑  收藏  举报