Difference between 'equals' and '==' in Java
来源:互联网 发布:java中sublist的用法 编辑:程序博客网 时间:2024/06/03 12:50
Java 中,“equals" 与"=="都可用于比较两个对象是否相等,可是比较的内容完全不同,使用时候要很明确这一点。
看例子:
public class equalsTS { public static void main(String[] args){ String a = "123"; String b = "456"; String c = "123"; String A = new String("ABC"); String C = new String("ABC"); System.out.println(a==b); System.out.println(a==c); System.out.println(A==C); System.out.println(A.equals(C)); }}
返回结果:
falsetruefalsetrue
解释:
- '=='操作符比较的是两个引用(references)是否相等,即比较引用的对象在内存中的location地址是否相同。所以a==b及A==C都是false,而a==c却返回的true,为何呢?这个和JVM的变量存储有直接关系,在JVM中,字符串等原生数据类型(非对象,如int,float,boolean,string等)在JVM中是存放在stack中的,而且在引用复制的时候,JVM会首先去Stack里寻找有没有已经存在的原生数据类型,如果有,将该数据的地址赋值给新的变量即可。所以a==c 会得到true。
- 'equals'方法则用于比较对象的content是否相等,这个就比较简单。两个对象A,C虽然是内存中不同地址的两个对象,但是它们的内容其实是一样的,都是一个为”ABC"的字符串,所以A.equals(C)返回的结果是true
- Difference between 'equals' and '==' in Java
- What’s the difference between ‘.equals()’ and ‘==’?
- Difference between Externalizable and Serializable in Java
- Difference between Vector and ArrayList in java?
- Difference between Comparator and Comparable in Java
- Difference between TreeMap and TreeSet in Java
- Difference between RegularEnumSet and JumboEnumSet in Java
- Difference between Comparator and Comparable in java
- Difference between Stack and Heap in Java
- Difference between ArrayList and Vector In java
- Difference between HashMap and Hashtable in Java
- Difference between Enumeration and Iterator in Java
- Difference between HashSet and HashMap in Java
- Difference between parseInt and valueOf in java?
- Difference between ArrayList and LinkedList in Java
- Difference between ConcurrentHashMap and Collections.synchronizedMap and Hashtable in Java
- Difference between ConcurrentHashMap and Collections.synchronizedMap and Hashtable in Java
- Java - Difference between Stack and Heap memory in Java
- MFC 程序入口和执行流程
- 《python编程入门经典》学习笔记第九章(一)
- 如何使用ckeditor控件实现华丽的富文本呢?
- linux socket的select函数例子
- uva 10391 - Compound Words
- Difference between 'equals' and '==' in Java
- POJ 3278 Catch That Cow bfs
- SQL数据库总结3
- WEB前端开发试题
- 手把手教你把Vim改装成一个IDE编程环境(图文)
- HDU 1787 数论
- 编译ffmpeg for iOS
- 武大集训第三周总结
- 【黑马程序员】Socket 网络编程