java中字符串比较的意外结果？

Question

public class HelloWorld {
    public static void main(String[] args) {
        String s1="yes";
        String s2="yes";

        System.out.println("-------The result is-----"+ s1==s2);
        System.out.println("-------The result is-----"+ (s1==s2));    
    }
}

Why the above code produce the output
"false"
-------The result is-----true

Answer 1

First of all, you should not be comparing strings with == , but with equals() .

There's also the issue of operator precedence. This:

"-------The result is-----"+ s1==s2

is the same as:

("-------The result is-----"+ s1) == s2

because + has higher precedence than == .

Answer 2

when you are comparing strings you should change up == to be .equals() due to the fact that .equals() compares the contents of the strings to each other or is used to compare objects. == checks for reference equality or is used to compare primitives. I changed your code below:

System.out.println("-------The result is-----"+ (s1.equals(s2)));

Answer 3

You are comparing the references of s1 and s2 , and since you defined them separately, they don't have the same references. To compare the strings, please use equals or equalsIgnoreCase

Answer 4

'+' > '=='

so

"-------The result is-----"+ s1==s2 becomes

("-------The result is-----"+ s1)==s2 and hence false.