字符串是常量；它们的值在创建之后不能更改。字符串缓冲区支持可变的字符串。因为 String 对象是不可变的，所以可以共享。
帮助文档这说 值 创建之后 不能改变 啥意思啊
String a="1";
String b ="2";
a=b;
System.out.println(a);
输出之后 还是2 a的值 变了 请问 怎么理解啊
------解决方案--------------------------------------------------------
String a="1";
String b ="2";
String c = a;//a和c都是指向同一个对象
a=b;
//看看c的值是否改变，如果c的值改变，表示String是可变的
System.out.println(a);
如果这个不理解，看这个例子
public class Bean {
public int num;
}
-----------
Bean a = new Bean();
Bean c = a;
a.num = 9;
//下面看看c.num有没有变
------解决方案--------------------------------------------------------
嗯，我表述的有问题，导致你理解错了，我说的final 不是说final class就不能修改了，而是具体类的构造属性的修饰final,这里面的char value[] ,offset等给你看一下String的源码
- Java code
public final class String implements java.io.Serializable, Comparable<String>, CharSequence{ /** The value is used for character storage. */ private final char value[]; /** The offset is the first index of the storage that is used. */ private final int offset; /** The count is the number of characters in the String. */ private final int count; public String(String original) { int size = original.count; char[] originalValue = original.value; char[] v; if (originalValue.length > size) { // The array representing the String is bigger than the new // String itself. Perhaps this constructor is being called // in order to trim the baggage, so make a copy of the array. int off = original.offset; v = Arrays.copyOfRange(originalValue, off, off+size); } else { // The array representing the String is the same // size as the String, so no point in making a copy. v = originalValue; } this.offset = 0; this.count = size; this.value = v; }}