String s1 = "coder";
String s2 = "coder";
String s3 = "coder" + s2;
**String s4 = "coder" + "coder";
String s5 = s1 + s2; **
System.out.println(s3 == s4);
System.out.println(s3 == s5);
System.out.println(s4 == "codercoder");
按道理说 + 号底层使用了stringbuilfer 拼接字符串,最后tostring()创建了一个新的string对象,s4 s5 不都是应该指向堆内存吗,为啥指向了字符串对象了??