String comparasions with == 1

[KillerProgrammer]

In the following code , why case 1 and case 3 returns "Not Equals" and case 2 returns "Equals" . The reference variable in case 1 is not the same from the string "String" in the JVM String Pool ? If not , case 2 should return "Not equals" , don't ? Same for case 3 that , in my way , should be identic to the case 1

public class Test
{
public static void main(String[] args)
{
//case 1
if(" String ".trim() == "String&quot
System.out.println("Equals"
else
System.out.println("Not Equals"

//case 2
if("String".substring(0) == "String&quot
System.out.println("Equals"
else
System.out.println("Not Equals"

//case 3
if(" String ".substring(1,7) == "String&quot
System.out.println("Equals"
else
System.out.println("Not Equals"

}
}

TIA

Thor

 

[palbano]

The bottom line is you should never use '==' on Strings unless you are wanting to compare Object references. Any other behavior you see is likely "undefined' and may change from VM to VM.

To find string equality you must use equals() and equalsIgnoreCase() etc.

-pete

 

[xutopia]

a star for that answer Gary

http://www.xutopia.com

Haran