String intern
char[] c = new char[]{'a','b'};
String str3 = new String(c);
str3.intern();// 先调用一次intern()
String str5 = new String(c);
System.out.println(str5.equals(str3));// true
System.out.println(str5 == str3);// false
System.out.println(str5.intern() == str3); // false ?这儿为什么是false