String s1 = "hello";
String s2 = "hello";
String s3 = "he" + "llo";
String s4 = "hel" + new String ("lo");
String s5 = new String ("hello");
String s6 = s5.intern(); //拿到s5对应的常量地址
String s7 = "h";
String s8 = "ello";
String s9 = s7 + s8;
String s10 = "h"+"ello";System.out.println(s1 == s2); //true
System.out.println(s1 == s3); //true
System.out.println(s1 == s4); //false
System.out.println(s1 == s5); //false
System.out.println(s4 == s5); //false
System.out.println(s1 == s6); //true
System.out.println(s1 == s9); //false 编译阶段，s7 s8都是变量，jvm不会做优化，会在堆里分配内存
System.out.println(s1 == s10); //true 编译阶段就处理成hello//jvm利用享元模式对String的优化，编译阶段对所能看到的放到常量池中，运行阶段直接使用Integer a =Integer.valueOf(100);
Integer b = 100;Integer c =Integer.valueOf(1000);
Integer d = 1000;System.out.println(a == b); //true
System.out.println(c == d); //false//Integer的valueof方法里在-128到127中有享元模式实现的缓存池，其外的都是调用new
//Long的valueof也是-128到127