Exception

[Vrushank Shukla]

class Propagate {
    public static void main(String[] args) {
	try {
	    //System.out.println(reverse(""));
 	    reverse("");
	}
	finally {
	    System.out.println("Program has completed");
	}
    }
    static String reverse(String s) {
	String reverseStr = "";
	for(int i = s.length() - 1; i >= 0; --i) {
	    reverseStr += s.charAt(i);
	}
	return reverseStr;
    }
}

Now, if the String length is 0, then reverse() method will throw an exception. But i didn't get any exception, the program compile and run fine. Why??

[Ankit Dan]

Which exception you were expecting?

[Vrushank Shukla]

I think it would be StringIndexOutOfBound.

[Ankit Dan]

From docs

public class StringIndexOutOfBoundsException extends IndexOutOfBoundsException

Thrown by String methods to indicate that an index is either negative or greater than the size of the string. For some methods such as the charAt method, this exception also is thrown when the index is equal to the size of the string.

But in your case there is no such condition and it is fine if you have a zero length string. Using s.charAt(2) will definitely throw a StringIndexOutOfBoundsException

Hope this helps

Ankit

[Shashank Gollapudi]

Vrushank Shukla wrote:

class Propagate {
    public static void main(String[] args) {
	try {
	    //System.out.println(reverse(""));
 	    reverse("");
	}
	finally {
	    System.out.println("Program has completed");
	}
    }
    static String reverse(String s) {
	String reverseStr = "";
	for(int i = s.length() - 1; i >= 0; --i) {
	    reverseStr += s.charAt(i);
	}
	return reverseStr;
    }
}

Now, if the String length is 0, then reverse() method will throw an exception. But i didn't get any exception, the program compile and run fine. Why??

Your code will not cause an exception because it never enters into the loop at all.
the length of the string that you sent is 0
so the value of i is set to -1 ( length of string - 1) which is 0 - 1
then it checks for condition i >=0 , where it fails and never enters inside the loop
Now it goes to the return statement directly

Hope this helps in getting why the exception dint occur.

[Vrushank Shukla]

Yes Shashank I got it. Thank you very much.

[Vrushank Shukla]

And yes Jeff i will mind it. Thank you.