Exception error for character array

Question

I am trying to write a program that display's the user's input in reverse. I know that there are better ways to do this but let me make a long story short by saying my teacher is not the most understanding of individuals that being said here's what I got so far:

public static void main(String[] args) 
{
    String input;
    int len;

    input = JOptionPane.showInputDialog(null, "Please enter a string value: ");
    len = input.length();
    char[] txt = new char[len];
    for (int i = 0; i <= len; i++)
    {
        txt[i] = input.charAt(i);
    }
    for (int j = len; j >= 0; j--)
    {
        System.out.print(txt[j]);
    }
}

The error I keep receiving is as follows:

Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 7 at program.main(program.java:28)

It points to the line:

System.out.print(txt[j]);

I understand that the error is saying that I have exceeded the limits of the array I'm just not seeing how. Any help or input will be greatly appreciated. Thank You.

possible duplicate of [What causes a java.lang.ArrayIndexOutOfBoundsException and how do I prevent it?](http://stackoverflow.com/questions/5554734/what-causes-a-java-lang-arrayindexoutofboundsexception-and-how-do-i-prevent-it) — njzk2, Nov 03 '14 at 22:04
As a side note, given the error you receive, I understand your teacher insisting on you getting this to work. Were I a teacher, I would expect a student to fully understand loops before starting to take shortcuts. — njzk2, Nov 03 '14 at 22:06

score 3 · Answer 1 · answered Nov 03 '14 at 22:02

3

Replace

for (int i = 0; i <= len; i++)

with

for (int i = 0; i < len; i++)

And

for (int j = len; j >= 0; j--) {

with

for (int j = len-1; j >= 0; j--) {

Array indexes are zero-based, and end at array length - 1.

answered Nov 03 '14 at 22:02

M A

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I knew it was something simple. Just a little burned out, I guess. Thanks for the help. – Altros Nov 03 '14 at 22:06

score 2 · Answer 2 · answered Nov 03 '14 at 22:03

2

Please change the looping condition in your for 1st loop !

i <= len

to

i < len

It goes from 0 ... n-1

Also you need to change initialization condition in 2nd loop

int j = len

to

int j = len-1

It goes from n-1 ... 0

answered Nov 03 '14 at 22:03

StackFlowed

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score 1 · Answer 3 · edited Nov 03 '14 at 23:28

1

Iterate over the array from (length-1) to 0. Array [length] is resulting in the IndexOutOfBoundsException.

Example code:

for (int i = 0; i < len; i++){
    txt[i] = input.charAt(i);
}
for (int j = len-1; j >= 0; j--){
    System.out.print(txt[j]);
}

edited Nov 03 '14 at 23:28

Rolf ツ

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answered Nov 03 '14 at 22:04

proko

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Exception error for character array

3 Answers3