Array Index Out OfBounds Help (Java)

Question

This Java program does a simple computation and it is suppose to output the numerical value of 123+1

(The output should be 124.) (Ignore the last "+" string.)

I got an error inside the if statement:

Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 4

I did a printout for arrayz[i-1] and arrayz[i+1] and it seems to printout 123 and 1 receptively, which is correct. So, I'm not sure what's wrong.

        String math = "123+1+";
        String arrayz[]={"123","+","1","+"};
        double total =0.0;

        int i=0;
        while(i<=(math.length()-1))        //don't bother with the last char
        {       i++;
            if(arrayz[i].equals("+"))
            {
                total = Double.parseDouble((String)arrayz[i-1]) + Double.parseDouble((String)arrayz[i+1]);

            }

        }

        System.out.println(total);

Increment i at the end of the loop, not the beginning.

Radiodef
– Radiodef

2013-12-28 06:13:36 +00:00
Commented Dec 28, 2013 at 6:13 — Radiodef
– Radiodef, Commented Dec 28, 2013 at 6:13

Suresh Atta · Accepted Answer · 2013-12-28 06:12:16Z

3

   while(i<=(math.length()-1))

math length is 6 and and in side loop your array length is 4

You might want to write

 while(i<=(arrayz.length-1))

edited Dec 28, 2013 at 6:12

answered Dec 28, 2013 at 6:06

Suresh Atta

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Comments

Christian Tapia · Accepted Answer · 2013-12-28 06:26:10Z

1

Since you are using the index i with the array arrayz, you must use arrayz.length instead of math.length()

Edit

This should work:

public static void main(String[] args)
{
    String math = "123+1+";
    String arrayz[] = { "123", "+", "1", "+" };
    double total = 0.0;

    int i = 0;

    // arrayz.length - 2 -> because you are accessing "arrayz[i + 1]", 
    // arrayz.length - 1 would be OK if the maximum index you were using were "arrayz[i] "
    while (i <= (arrayz.length - 2)) //don't bother with the last char
    {           
        if (arrayz[i].equals("+")) {
            total = Double.parseDouble((String) arrayz[i - 1]) + Double.parseDouble((String) arrayz[i + 1]);
        }
        i++; // Increment at the end of the loop
    }

    System.out.println(total);
}

edited Dec 28, 2013 at 6:26

answered Dec 28, 2013 at 6:06

Christian Tapia

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6 Comments

Christian Tapia Over a year ago

Try using length without ()

Christian Tapia Over a year ago

No way! What's the error? You may increment (i++) after all the computations, in other words, at the end of the loop. You could use a for loop to avoid this.

Jonathan Lam Over a year ago

it works when I do while(i<=(arrayz.length-3)) but it doesn't look efficient.

Christian Tapia Over a year ago

What happen is that you are accessing with the index i+1, you must correct this too.

Jonathan Lam Over a year ago

yup, I put the i++ after the if statement. I'm still getting the ArrayIndexOutOfBoundsException error

|

Yagnesh Agola · Accepted Answer · 2013-12-28 06:34:22Z

1

You are looping over the string math, at the same time accessing elements of arrayz inside your loop, and thinking that they have the same elements and the same length.
What I suggest you, is to use instead of math String (you can omit it in this case but I assume you can't in general for some criteria), you can use an array of type String, so that 123 in your example would be the first element arrayz[0].

edited Dec 28, 2013 at 6:34

Yagnesh Agola

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answered Dec 28, 2013 at 6:28

Curcuma_

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