string和string new之间的区别 [英] difference between string and string new

问题描述

字符串s =abc和字符串s =新字符串（abc）之间有什么区别。



我搜索了它，有些人说没有区别，有人说是。



任何人都可以解释我或给这些网站链接。





谢谢。

Hi ,

What is the difference between string s="abc" and string s =new string("abc").

I searched for it,some say no difference some say yes .

can anybody explain me or give links to the sites.


Thanks.

推荐答案

例如：

For Example:

String s = "Marcus";

这是一个字符串文字。

It is a string literal.

String s2 = new String("Marcus");

创建一个新实例，因为你用新的创建了一个字符串运营商。



但是如果你创建了一个新的字符串，例如

String s1 =Marcus



首先它搜索字符串池中是否存在字符串Marcus（在这种情况下，因为它已经存在），现在它只是将它重新分配给s1。

A new instance is created as you have created the string with the new operator.

But again if you have created a new string like
String s1 = "Marcus"

First it searches if the string "Marcus" is there in the string pool,(in this case,as it is already there),now it just reassigns the same to s1.

1-字符串对象池问题



字符串对象是不可变的;这就是说当你说

1- String objects pool issue

String object is immutable; thats mean when you say

String s = "Mohammed";
s += "El-Adawi";

运行时这意味着创建了一个新的字符串Mohammed El-adawi

并分配给引用s

和字符串Mohammed现在是合格的for gc



为什么sun必须这样做？，因为String文字

（之间的任何东西都被编译器重新识别为String literal ）

由编译器放入字符串池中，然后如果compilar再次找到相同的文字，例如

on runtime this means that a new String "Mohammed El-adawi" is created
and assigned to reference s
and String "Mohammed" now is eligable for gc

why sun have to do that ?, because String literals
(any thing between " " is reccognized by compiler as String literal)
are put by compiler in String pool, then if compilar found the same literal again for example

String s = "abc";
String m = "abc"; // compiler now found the same String literal

编译器将有一个abc副本，并将s，m分配给相同的字符串文字，（在运行时）构造并赋予s的一个对象，m）



如果m改变字符串，s将指向错误的东西，这就是为什么String是不可变的。



2-回答你的问题

compiler will have one copy of "abc" and will assign both s,m to the same String literal, (at run time one object constructed and asigned to s,m)

if m change the String, s will point to the wrong thing, thats why String is immutable.

2- answer to your question

String s = "Marcus"; // One String object is built and assigned to s.

String s2 = new String("Marcus");
/* now compiler found "Marcus" in the pool
so it will not create a new object
new operator creates new object contains 
Marcus at runtime
*/


String s3 = new String("Mohammed Not Marcus");
// compiler adds "Mohammed Not Marcus" to String pool but with no 
// reference assignment, and String object created and assigned to S3 // at runtime 

3-另一件事

3- Another thing

String s1 = "abc";
String s2 = "abc"; 
System.out.println(s1 == s2); // true

但

but

String s1 = "abc";
String s2 = new String ("abc");
System.out.println(s1 == s2); // false 

我希望这是有帮助的

I hope that is helpfull

访问链接

很好的解释与数字将明确的疑惑:)

主题： 2.1字符串文字与字符串对象

http://www3.ntu.edu.sg/home/ehchua/programming/java/J3d_String.html [ ^ ]

Happy编码！

：）

visit link
nice explanation with figure that will clear doubts :)
Topic : 2.1 String Literal vs. String Object
http://www3.ntu.edu.sg/home/ehchua/programming/java/J3d_String.html[^]
Happy Coding!
:)

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