I have an issue with returning an array from a method

Question

The program compiles but it gives the following error:

Two
One
Three
Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 3
at testingN.printArray(testingN.java:19)
at testingN.main(testingN.java:10)

I am really new into Java ( and programming ) and I'm stuck with this.

public class testingN 
{
    public static void main(String[] args) 
    {
        String[] names = new String[3];
        names[0] = "Two";
        names[1] = "One";
        names[2] = "Three";
        printArray(names);
    }
    public static String printArray(String[] data) 
    {
        int i;
        for (i = 0; i < data.length; i++) 
        {
          System.out.println(data[i]);
        }
        return data[i];
    }
}

return data[i]; is using index 3, because i is incremented before the loop exits. — jonhopkins
– jonhopkins, Commented Oct 28, 2013 at 18:28
Like @jonhopkins said, if you want to return the last element of the array you should return data[i-1];. That said, a method that prints should be declared as void (not return anything). If you want to implement another functionality you should do it somewhere else... — Nir Alfasi
– Nir Alfasi, Commented Oct 28, 2013 at 18:29
Do you really need to return anything? It seems that you could just make the method void and take out the return statement. — jlars62
– jlars62, Commented Oct 28, 2013 at 18:29
Could you please implement a simple functionality somewhere else (new class or ?) for me just to see an example because I am really getting confused? :( I do not want to use void method, but a return method ! — I i i
– I i i, Commented Oct 28, 2013 at 18:35
To be honest, what I really need to do is to create an array of numbers (input with scanner) and given this array I want to return another array with new numbers(I have to use some formula in the return method to convert the numbers) — I i i
– I i i, Commented Oct 28, 2013 at 18:38

Chill · Accepted Answer · 2013-10-28 18:33:05Z

2

It's because of the way a for loop works.

for (*initialization*; *some boolean condition*; *action to perform each loop*) {
    //...
}

A for loop works as follows:

It begins by running the code in the initialization section. In your case, it sets i = 0
It runs the contents of the loop
It performs the action. In your case i++.
It checks the boolean condition. If it is true, it goes to step 2. Otherwise it exits the loop. In your case the condition is i < data.length.

Since step 3 happens before the condition is checked, your i value is going to be 1 larger than the array size -1. That is, it will be the index exactly one larger than the last index of the array. So return data[i]; gives you an out of bounds exception.

answered Oct 28, 2013 at 18:33

Chill

1,1136 silver badges13 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Hussain Akhtar Wahid 'Ghouri' · Accepted Answer · 2013-10-28 18:56:32Z

0

public class testingN 
{
    public static void main(String[] args) 
    {
        String[] names = new String[3];
        names[0] = "Two";
        names[1] = "One";
        names[2] = "Three";
        printArray(names);
    }
    public static void printArray(String[] data) 
    {
        for (int i = 0; i < data.length; i++) 
        {
          System.out.println(data[i]);
        }
    }
}

answered Oct 28, 2013 at 18:56

Hussain Akhtar Wahid 'Ghouri'

6,6379 gold badges52 silver badges87 bronze badges

Collectives™ on Stack Overflow

I have an issue with returning an array from a method

2 Answers 2

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related