intern()方法和前面说的equals()方法关系密切，从public native String intern()看出，它是Java的本地方法，我们先来看看Java文档里的描述：
Returns a canonical representation for the string object.A pool of strings, initially empty, is maintained privately by the
class String.When the intern method is invoked, if the pool already contains a
string equal to this String object as determined by
theequals(Object) method, then the string from the pool is
returned. Otherwise, this String object is added to the
pool and a reference to this String object is returned.
It follows that for any two strings s and t,
s.intern()==t.intern() is true if and only if s.equals(t) is true.
All literal strings and string-valued constant expressions are interned.
@return a string that has the same contents as this string, but is
guaranteed to be from a pool of unique strings.
意思就是说，返回字符串一个规范的表示。进一步解释：有两个字符串s和t，s.equals(t),则s.intern()==t.intern().
举个例子：
public class StringTest {
public static void main(String[] args) {
String s = new String("abc");
String s1 = "abc";
String s2 = "abc";
String s3 = s.intern();
System.out.println(s == s1);//false
System.out.println(s == s2);//false
System.out.println(s == s3);//false
System.out.println(s1 == s3);//true
}
}
输出结果如注释所示，前两个结果前面已经说的很清楚了，现在拿最后一个说明，首先看看s3 = s.intern()这句，当调用s.intern()这句的时候，先去字符串常量池中找，是否有abc这个串，如果没有，则新增，同时返回引用，如果有，则返回已经存在的引用，此处s1和s2都指向常量池中的abc对象，所以此处是存在的，调用s.intern()后，s3和s1、s2指向同一个对象，所以s1==s3返回的是true。intern()做到了一个很不寻常的行为：在运行期动态的在方法区创建对象，一般只有像new关键字可以在运行期在堆上面创建对象，所以此处比较特殊。属于及时编译的概念。
一般常见的字符串处理函数就这些，其它的还有很多，就不一一列举。