当我在 Java 中创建一个新的 String 时，它是用 null 还是用“”初始化？
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When I create a new String in Java, is it initialized with null or with " "?
提问by
Here's my test code:
这是我的测试代码：
String foo = new String();
System.out.println(foo);
The output is blank and a new line is written. Since I'm new to Java, I don't know whether it made a " " string, or nulls are handled as blank lines.
输出为空白并写入一个新行。由于我是 Java 新手，我不知道它是否制作了 " " 字符串，或者空值被视为空行。
采纳答案by Chris Dennett
The string is initialised with no characters, or "" internally.
该字符串在内部初始化时没有字符或 ""。
public String() {
this.offset = 0;
this.count = 0;
this.value = new char[0];
}
The above source is taken from the Java source code. As the other poster pointed out, references can either be null or point to an object, if you create a String object and get a reference to point to it, that reference will not be null.
以上源码取自Java源代码。正如另一位海报指出的那样，引用可以为空或指向一个对象，如果您创建一个 String 对象并获得指向它的引用，则该引用不会为空。
回答by DJClayworth
"null" is a value for a variable, not a value for a String. "foo" can have null value, but an actual String cannot. What you have done is create a new empty String (as the documentation for the constructor says) and assigned it to foo.
“null”是变量的值，而不是字符串的值。“foo”可以有空值，但实际的字符串不能。您所做的是创建一个新的空字符串（如构造函数的文档所述）并将其分配给 foo。
回答by Jay
new String() creates a String of length zero. If you simply said "String foo;" as a member variable, it would be initialized to null. If you say "String foo;" as a function variable, it is undefined, and will give a compile error if you try to use it without assigning a value.
new String() 创建一个长度为零的字符串。如果你只是说“String foo;” 作为成员变量，它会被初始化为 null。如果你说“String foo;” 作为函数变量，它是未定义的，如果您尝试使用它而不赋值，则会出现编译错误。
回答by someguy
A new line is printed because you called the println() method, which prints a line after printing whatever argument you passed. new String() will return "".
打印新行是因为您调用了 println() 方法，该方法在打印您传递的任何参数后打印一行。new String() 将返回 ""。
回答by OscarRyz
It is initialized with ""( empty string )
它用""（空字符串）初始化
public class StringTest {
public static void main( String [] args ) {
System.out.println( "".equals(new String()));
}
}
prints:
印刷：
true
