trim() method in String

[Yea Mua]

Hi all,

Here is a tricky question from abhilash's quiz:

" String ".trim() == "String" returns false
"String".trim() == "String" returns true
" String ".trim() == " String ".trim() returns false
"String".trim() == "String".trim() returns true

One more Q:

"String".toUpperCase() == "STRING" returns false

Any idea on what happened behind the scene?

Thanks!

[Seetharaman Venkatasamy]

that is because " String ".trim() returns new String("String"); and "String".trim() returns *this* object;i.e, the same "String".

[Muneeswaran Balasubramanian]

Added with Seetharaman,

By performing the operations like trim,toUpperCase,toLowerCase etc,change the state of the String,it returns the new String object.Otherwise it returs the same string object like this.So it returns true.
Ex:

System.out.println("RAM".toUpperCase() == "RAM");//true
System.out.println("Ram".toUpperCase() == "RAM");//false

Hope this helps.

[Javin Paul]

how about substring() method , does it return the same String object if we specify begin and end index such that it return whole string ?

[Seetharaman Venkatasamy]

Javin Paul wrote:how about substring() method , does it return the same String object if we specify begin and end index such that it return whole string ?

Yes, it returns the same this string! why cant you test this?

[Javin Paul]

just thought to put you in front of guru and benefit to others, not had my IDE opened thanks anyway

[Yea Mua]

Hi Muneeswaran and Seetharaman,

Thanks for the response, and I believe you guys must work for the exam team

Regarding this problem, I have a follow-up question upon your answers.

In my opinion, Java utilizes a String pool that virtually only one instance of String could exist. Strings with same value just means their reference all point to the only one instance. So how could a new String (after state change by applying trim,toUpperCase,toLowerCase etc) be created provided one has already lived there?

Thanks!

Muneeswaran Balasubramanian wrote:Added with Seetharaman,

By performing the operations like trim,toUpperCase,toLowerCase etc,change the state of the String,it returns the new String object.Otherwise it returs the same string object like this.So it returns true.
Ex:

System.out.println("RAM".toUpperCase() == "RAM");//true
System.out.println("Ram".toUpperCase() == "RAM");//false

Hope this helps.

[Yea Mua]

Call for a complete answer guys ~~