What is the wrong if i compare string using == operator in java instead of equals() method

Question

As I know

== is used to compare references. .equals() is used to compare content.

There is a string pool is available in java. For example I created a string as follows

String s ="ABC"; then address for this is suppose 12345

When I use same string i.e "ABC" same string will share in both places. That means addresses for both strings are same.

== is for compare references .In this case address for both strings are same.Then why I need to go for equals() method.Please correct me if I am wrong.

public class StringComparison {

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

    if(s1 == s2)
        System.out.println("BOTH ARE  == ");
    else
        System.out.println("BOTH ARE != ");


    String s3 = new String("test");
    String s4 = new String("test");

    if(s3 == s4)
        System.out.println("BOTH ARE  == ");
    else
        System.out.println("BOTH ARE != ");

  }
}

OUTPUT:
BOTH ARE  == 
BOTH ARE !=

But the reference link says new String("test") == new String("test") ==> false

I don't think that `String` object is sharing the same reference, only that it's contents points to that address...so the `String` objects are all different/unique references — MadProgrammer, Sep 26 '13 at 04:52
@MadProgrammer: If `==` is true (which it is sometimes) then the two `String`s do indeed share the same reference (i.e. are the same object). — Thilo, Sep 26 '13 at 04:54
@devnull thank u so much.This is what i am looking for.But because of bad keyword formatting i did not find that link — java developer 2222, Sep 26 '13 at 04:57
@javadeveloper2222 No, they basically mean the same thing... — MadProgrammer, Sep 26 '13 at 05:00
@Thilo I would suggest that they are the same Object then, by that extension, they have to have the same content but `new String("Hello") == new String("Hello")` would be `false` as I understand the question, it's more about why `"Hello" == "Hello"` would be false if the text "Hello" has being interned into the String pool — MadProgrammer, Sep 26 '13 at 05:01
@java developer 2222 - please check whether the question exists in SOF before posting.. — TheLostMind, Sep 26 '13 at 05:10
@MadProgrammer all these people are fast to mark this as duplicate.But no one has the dare to answer it. — java developer 2222, Sep 26 '13 at 05:10
@javadeveloper2222 I thought it was a duplicate at first, but I think it goes a little deeper then why we use `equals` — MadProgrammer, Sep 26 '13 at 05:12
This will have something to with how the compiler to deals with `"test"` as opposed to `new String("test")`. I don't have the knowledge to be 100% correct, but I would surmise that the compiler is producing it's own optimisation in such a way that `"test"` becomes the same object reference, whereas `new String("test")` has to, by it's nature, create a new object each time... — MadProgrammer, Sep 26 '13 at 05:14
This link would give a good explanation for it. http://www.thejavageek.com/2013/07/27/string-comparison-with-equals-and-assignment-operator/ — Prasad Kharkar, Sep 26 '13 at 05:32
@PrasadKharkar String aName = new String("prasad"); is different with String aName = "prasad"; — java developer 2222, Sep 26 '13 at 05:43
aName = "prasad" is in string constant pool and new String("prasad") creates a new String object. — Prasad Kharkar, Sep 26 '13 at 06:10

What is the wrong if i compare string using == operator in java instead of equals() method

0 Answers0