Thread: Java String Pool - Beginner Question

Hi.

I have a question about string pool.
There is a code:

public static void main(String[] args) {
        String s1 = new String("ABC");
        String s2 = new String("ABC");
        String s3 = "ABC";
        String s4 = "ABC";
        final String s5 = "AB";
        String s6 = "C";
 
        System.out.println(s1 == s2);
        System.out.println(s2 == s3);
        System.out.println(s3 == s4);
        System.out.println(s4 == s5 + s6);
        System.out.println(s4 == s5 + "C");
}

General rules as I understand are that literals (like "ABC") go to String Poll, objects (like new String()) go to Java Heap.
In this way,
first println has "false"
2 - "false"
3 - "true"
4 - "false", because object plus literal goes Java Heap
5 - "true"

I have question for you about fifth println.
If I removed word final, I would get result false.

Why? How do strings behave in fifth line?
What exactly word final does?
As I know final variables go to something special memory space. For example global cache. I am not sure.

OK
Can you please explain me about fifth println with final and without final?
I will thankful for doc references, because I couldn't find anything.

Sorry, I have never studied the implementation of String pools. I think that any code that relies on knowing what String is in the pool and what String in not in the pool is weak/bad code. You should always use the equals method to compare String objects.

Take a look in the java specs: http://docs.oracle.com/javase/specs/