blocks|key|1663911|text|通常，这表示某人在初始化时不喜欢声明的新风格C%2B%2B。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1663912|在C语言时代，在内部作用域中定义自动变量并不被认为是一种好的形式；C%2B%2B消除了解析器的限制，并对其进行了扩展。|1663913|所以你可以看到代码中有|1663914|int+q;
for(q=0;q<MAX;q%2B%2B){
++++String+s;
++++int+ix;
++++//+other+stuff
++++s+=+new+String("Hello,+there!");
++++//+do+something+with+s
}|code-block|syntax|javascript|1663915|在极端情况下，所有的声明可能都在函数的顶部，而不是在封闭的作用域中，比如这里的for循环。|offset|length|style|CODE|1663916|不过，通常情况下，这会导致字符串ctor被调用一次，并丢弃生成的字符串。(正是为了避免这种情况，Stroustrup才允许在代码中的任何位置进行声明。)所以你是对的，它是不必要的，充其量也是糟糕的风格，甚至可能是糟糕的。|1663917|entityMap^0|0|0|0|0|13|3|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|V|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|W|8|@]|9|@]|A|$]]|$1|F|3|G|5|H|7|X|8|@]|9|@]|A|$I|J]]|$1|K|3|L|5|6|7|Y|8|@$M|Z|N|10|O|P]]|9|@]|A|$]]|$1|Q|3|R|5|6|7|11|8|@]|9|@]|A|$]]|$1|S|3|-4|5|6|7|12|8|@]|9|@]|A|$]]]|T|$]]

Generally, this indicates someone who isn't comfortable with the new-fashioned C++ style of declaring when initialized. 

Back in the C days, it wasn't considered good form to define auto variables in an inner scope; C++ eliminated the parser restriction, and Java extended that.

So you see code that has

<pre><code>int q;
for(q=0;q&lt;MAX;q++){
 String s;
 int ix;
 // other stuff
 s = new String("Hello, there!");
 // do something with s
}
</code></pre>

In the extreme case, all the declarations may be at the top of a function, and not in enclosed scopes like the <code>for</code> loop here.

IN general, though, the effect of this is to cause a String ctor to be called once, and the resulting String thrown away. (The desire to avoid this is just what led Stroustrup to allow declarations anywhere in the code.) So you are correct that it's unnecessary and bad style at best, and possibly actually bad.

blocks|key|1449041|text|我发现它唯一有用的时候是在声明锁变量时：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1449042|private+final+String+lock+=+new+String("Database+lock");

....

synchronized(lock)
{
++++//+do+something
}|code-block|syntax|javascript|1449043|在这种情况下，像Eclipse这样的调试工具将在列出线程当前持有或等待的锁时显示该字符串。你必须使用"new+String"，即分配一个新的String对象，因为否则共享的string文本可能会在其他一些不相关的代码中被锁定。|1449044|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

The only time I have found this useful is in declaring lock variables:

<pre><code>private final String lock = new String("Database lock");

....

synchronized(lock)
{
 // do something
}
</code></pre>

In this case, debugging tools like Eclipse will show the string when listing what locks a thread currently holds or is waiting for. You have to use "new String", i.e. allocate a new String object, because otherwise a shared string literal could possibly be locked in some other unrelated code.

blocks|key|1449088|text|有两种方法可以在Java中创建字符串。下面是两种方法的示例:+1)声明一个String类型的变量(Java中的一个类)，并将其赋给一个应该放在双引号中的值。这将在内存的字符串池区域中创建一个字符串。例如:+String+str+=+"JAVA"；|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1449089|2)使用String类的构造函数，传入一个字符串(双引号内)作为参数。例如:+String+s=+new+String("+JAVA+")；这将在主内存中创建一个新的字符串JAVA，如果该字符串尚未出现在字符串池中，还会在字符串池中创建该字符串。|1449090|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|F|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|G|8|@]|9|@]|A|$]]|$1|D|3|-4|5|6|7|H|8|@]|9|@]|A|$]]]|E|$]]

There are two ways in which Strings can be created in Java. Following are the examples for both the ways:
1) Declare a variable of type String(a class in Java) and assign it to a value which should be put between double quotes. This will create a string in the string pool area of memory.
eg: String str = "JAVA";

2)Use the constructor of String class and pass a string(within double quotes) as an argument.
eg: String s = new String("JAVA");
This will create a new string JAVA in the main memory and also in the string pool if this string is not already present in string pool.

blocks|key|1664050|text|Software+Monkey和Ruggs描述的这个构造器的唯一实用工具似乎已经从JDK7中消失了。在类String中不再有offset字段，子字符串始终使用|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1664051|Arrays.copyOfRange(char[]+original,+int+from,+int+to)+|code-block|syntax|javascript|1664052|若要修剪副本的字符数组，请执行以下操作。|1664053|entityMap^0|1Q|6|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@$9|P|A|Q|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|R|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|S|8|@]|D|@]|E|$]]|$1|M|3|-4|5|6|7|T|8|@]|D|@]|E|$]]]|N|$]]

The sole utility for this constructor described by Software Monkey and Ruggs seems to have disappeared from JDK7.
There is no longer an <code>offset</code> field in class String, and substring always use

<pre><code>Arrays.copyOfRange(char[] original, int from, int to) 
</code></pre>

to trim the char array for the copy.

While looking at online code samples, I have sometimes come across an assignment of a String constant to a String object via the use of the new operator.

For example:

<pre><code>String s;
...
s = new String("Hello World");
</code></pre>

This, of course, compared to

<pre><code>s = "Hello World";
</code></pre>

I'm not familiar with this syntax and have no idea what the purpose or effect would be. 
Since String constants typically get stored in the constant pool and then in whatever representation the JVM has for dealing with String constants, would anything even be allocated on the heap?

What is the purpose of the expression "new String(...)" in Java?

Eclipse

Java

在查看在线代码示例时，我有时会遇到通过使用new运算符将字符串常量赋值给String对象的情况。例如：String s;...s = new String("Hello World");当然，这与s = "Hello World";我不熟悉这个语法，也不知道它的目的和效果是什么。由于字符串常量通常存储在常量池中，然后以...

问表达式"new String(...)“的用途是什么？在Java中？
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