String Methods

[rahul V kumar]

Can anyone whats going behind the scenes for the followig code snippets
Q1)
******************************************
if(" String ".trim() == "String")
System.out.println("Equal");
else
System.out.println("Not Equal");
Answer is "Not Equal"
******************************************
Q2)
******************************************
if("String".substring(0,6) == "String")
System.out.println("Equal");
else
System.out.println("Not Equal");
Answer is "Equal"
******************************************
Q3)
******************************************
if("String".replace('g','G') == "String".replace('g','G'))
System.out.println("Equal");
else
System.out.println("Not Equal");
Answer is "Not Equal"
******************************************
Q4)
**********************************************
if("String".replace('t','t') == "String")
System.out.println("Equal");
else
System.out.println("Not Equal");
Answer is "Equal"
********************************************
Thanks

[Corey McGlone]

Strings are immutable. That means that they can never be changed. Because of this, most of the methods of the String class behave a certain way - if the result of the method is a different String than the original, they create a brand new String object and return it. If the result is the same, however, rather than creating a useless object, the method simply returns the original String that was passed as an argument back.
I hope that helps,
Corey

[rahul V kumar]

Thanks. That was really helpful.

[Robbie kyodo]

String s1 = "ABC";
String s2 = new String (s1);
String s3 = new String (s1);
if (s2 == s3) // return false why ??
s2.trim() == s2.toUpperCase() // true why ??
can u explain using below diagram ?
s2 -> s1 -> "ABC"
s3 ->

[Rajinder Yadav]

Read what Corey said earlier
s1 is created on constant string constant pool
s2 and s3 are created on the heap
s1 -> "ABC"
s2 -> "ABC"
s3 -> "ABC"