Strings

[amarkirt saroay]

public String testme(){
String s="Fred"; //line 1
s=s+"47"; //line 2
s=s.substring(2,5); //line 3
s=s.toUpperCase(); //line 4
return s.toString();
}
How many string objects will b created when this method is invoked?

Ans was 3.
How ? Are lines 3 and 4 not creating new Strings in the pool?

[Ben Souther]

"amarkirt amarkirt",
Please check your private messages for an important administrative matter.

[Jelle Klap]

public String testme(){
  String s="Fred";      //line 1
  s=s+"47";             //line 2
  s=s.substring(2,5);   //line 3
  s=s.toUpperCase();    //line 4
  return s.toString();  //line 5
}

Line 1: No string will be created, because "Fred" is a compile time literal that will have already been present in the string constant pool.

Line 2: A single new String object will be created for value "Fred47", again "47" itself is a compile time literal (see comment for Line 1).
Total number of new String objects created so far: 1

Line 3: A single new String object will be created by the subString method for value "ed4".
Total number of new String objects created so far: 2

Line 4: A single new String object will be created by the toUpperCase method for value "ED4".
Total number of new String objects created so far: 3

Line 5: The toString method will just return the reference to the String object created at line 4.

Total number of new String objects created per method call: 3

[Nabila Mohammad]

I don't understand
How come ther is not string created for "Fred"
What do you mean by compilte time literal that will be already present.How do you know it's already present in the string constant pool?

Oh Boy!! This question has been coming up so many times and I am still not clear with it!!!

[Jelle Klap]

Well, in the previous code snippet the string literal "Fred" will be added to the per-class constant pool by the compiler (compile-time). So before the testme method is called at run-time the string literal "Fred" will already be present in the constant pool, hence no new String object will be created for literal value "Fred". The same is true for the string literal "47".
[ March 20, 2008: Message edited by: Jelle Klap ]