String 的比较问题。
String s = "yz";
String s1 = "xyz";
String s2 = "x"+"yz";
String s3 = "x"+new String("yz");
String s4=new String("xyz");
String s5 = "x"+s;
System.out.println(s1==s2);true
System.out.println(s1==s3);false
System.out.println(s1==s4);false
System.out.println(s4==s3);false
System.out.println(s2==s5);false
能详细解释下么?