String equality

[Ramesh Sahu]

import java.io.*;
class StringTest {

public static void main(String args[]) throws IOException{
System.out.println("s12"==((" s12 ".trim())));
System.out.println( "String" == "String".replace('t','t') );


}
}

running the above code gives output as
false
true

How String pool used by the JVM works in the above two statements?

[ramesh maredu]

trim method internally uses substring() method which returns new string.

replace(char oldChar, char newChar)

implementation of this class returns same string if oldChar is equal to newChar.

[Ramesh Sahu]

Thanks Ramesh
I got that

[Madhukar Ojha]

Originally posted by Ramesh Sahu:
import java.io.*;
class StringTest {

public static void main(String args[]) throws IOException{
System.out.println("s12"==((" s12 ".trim())));
System.out.println( "String" == "String".replace('t','t') );


}
}

You should always remember that
Besides String literals and compile time constant expressions
all String objects are created at run-time same as other objects.

   
   System.out.println("s12"==((" s12 ".trim())));
 

When you say " s12 ".trim() then " s12 " object goes String pool
whereas string created on " s12 ".trim() invocation is created at
run-time hence distinct.

Hence "12"==((" s12 ".trim()))
returns false

When you invoke replace() , it returns same object reference if both
arguments are same.

    "String" == "String".replace('t','t')

Since both arguments are same hence replace method returns same reference
hence it returns true.

[Seetharaman Venkatasamy]

Originally posted by Ramesh Sahu:
System.out.println("s12"==((" s12 ".trim())));
System.out.println( "String" == "String".replace('t','t') );

Hello,

1. "s12" and " s12 " is different---- so,false

2. "String".replace('t','t') is nothing but "String"---so,true

Hope This Helps