String s1 = “abc”;
   String s2 = new String(“abc”);
   System.out.println(s1==s2);
   String s3 = “你好吗”;
   String s4 =”你”;
   String s5 =”好吗”;
   System.out.println(s3==(s4+s5))  

a)true true
b)false true
c)true flase
d)false false

==比较引用数据类型比较的是地址值；d