In this code why a new String object is created, than not using println(copyTo)?

[Varuna Seneviratna]

char[] copyFrom = { 'd', 'e', 'c', 'a', 'f', 'f', 'e',
    'i', 'n', 'a', 't', 'e', 'd' };
        char[] copyTo = new char[7];
 
        System.arraycopy(copyFrom, 2, copyTo, 0, 7);
        System.out.println(new String(copyTo));

In this code why a new String object is created, than not using println(copyTo)?.What is the difference?

Varuna

[Gautam Sathe]

Hello!

println() method which is a memebr of PrintStream class can take both char array as well as String object as a parameter. So whether you use char array (in this case copyTo) or String object the output is same. The only difference is the type of parameter passed to the println method.

Gautam.

[Varuna Seneviratna]

Gautam!

What was in my mind was what made anybody without straightly using copyTo in the println(), create a String object.This was from the Sun java Tutorials.


Varuna

[Campbell Ritchie]

The real problem is that arrays don't have overridden toString() methods. Have a look at the Object class, Java Language Specification about arrays, and the )]String class constructor.

Now work out what that Java Tutorial method would print if you didn't create the new String! Try it with
System.out.println(new String(copyTo));
and
System.out.println(copyTo);
The idea of that example is to show you how the arraycopy method works, so they miss out the bit about new String!

[Campbell Ritchie]

If one of my links doesn't work, copy and paste this:

http://java.sun.com/javase/6/docs/api/java/lang/String.html#String(char[])

[Ernest Friedman-Hill]

Actually, it would print the same thing. There's an overloaded version of println() that accepts a char[] argument and prints the characters as if they were a String.

The reason the code makes a copy of some -- not all! -- of the characters is because it is demonstrating how the System.arraycopy() method is used.

The reason that the programmer creates the new String is harder to imagine. The overloaded println(char[]) has been present since the very first JDK release. Perhaps the coder was simply new to Java? Nobody's perfect, even Sun Micro employees.

[Campbell Ritchie]

Yes, I see what you mean; I had expected to get the [C@ab123456 format! It is a bit pointless creating a new String object.