how to know when a String went to the string constant pool

[Jeane Lindford]

hi all
how to know when a String went to the string constant pool
for example

public class BoomBox2 {

   public static void main(String[] args) {
      new BoomBox2().go(args);
   }

   void go(String[] args) {
      if (args[0].equals("x"))
         System.out.print("x ");
      if (args[0] == "x")
         System.out.println("x2 ");
   }

}

if I pass "new BoomBox2().go(new String[]{"x"});" both SOP are executed
but if I execute this code via commandline like

java BoomBox2 x

only the first SOP are executed
why in this second invocation the x passed via command line arg does not went to the string constant pool?
how do I know that a String comparison via == will return true or false?
thanks

[Ikpefua Jacob-Obinyan]

Hello Jeane, to the best of my knowledge the second invocation

java BoomBox2 x

returns an array containing a new String object;

{new String("x")}

when you use the new keyword to create a string, the object resides in the heap, which off course has a different "address" from the string-constant-pool, hence the strings reference variable refers to that object in the heap, and NOT the string-constant-pool.
The == returns true if both references refers to the SAME object.
The equals() method returns true if and ONLY if the reference variable type and object types are equal. java implemented the equals() method in Strings and Wrapper classes in such a way that it returns true if the reference AND object types are MEANINGFULLY equal eg;

String s = new String("x");
String s2 = new String("x");
System.out.println(s.equals(s2));

Output

true

HTH

Regards

Ikpefua

[Chandella Montero]

Hi Jeanne,

I don't know how you are meant to know either, I was asking the same question as you. When you pass a String via the command line, then a new String is created (or it looks like it). Is this ALWAYS? It is because it is?

[Ikpefua Jacob-Obinyan]

Hello Guys, I found a link that explains in full details EVERYTHING you need to know about Strings, String-Constant-Pool etc... Take your time and read carefully: STRINGS, LITERALLY

[Chandella Montero]

Voilà:

Strings created at run-time will always be distinct from those created from String Literals.

Cheers once again, Ikpefua .

[Ruobo Wang]

this thread's info helped a lot , thank you!