Array Out of Bounds Exception with Hashmap Java

Question

I'm trying to put together a hashmap with a char array as the value and a string as the key. I'm trying to print out the Keys and Values but keep getting an array out of bounds exception. I'm not sure what the problem is. (Also I might be trying to print out the map incorrectly; I'm kind of just going off other posts). Can someone help me out with the logic of this. Thanks for any help. Here is my code:

public class MapExample {

     public static void main(String[] args) {

       Map<String,char[]> mp=new HashMap<String, char[]>();

       char[] words = new char[2];
       words[0] = 'a';
       words[1] = 'b';
       words[2] = 'c';

       mp.put("1", words);
       mp.put("2", words);
       mp.put("3", words);

       Set s=mp.entrySet();
       Iterator it=s.iterator();

        while(it.hasNext())
        {           
            Map.Entry m =(Map.Entry)it.next();
            int key=(Integer)m.getKey();
            String value=(String)m.getValue();

            System.out.println("Key :"+key+"  Value :"+value);
        }
    }
}

Reimeus · Accepted Answer · 2013-06-14 15:14:23Z

7

Arrays are zero based. Increase the array size of words so that you can assign an element at index 2

char[] words = new char[3];

answered Jun 14, 2013 at 15:14

Reimeus

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4 Comments

David Over a year ago

Ok, but now I get java.lang.String cannot be cast to java.lang.Integer as an error, any ideas?

thejh Over a year ago

@dave: If you have another question, please post another question instead of discussing in the comments.

Reimeus Over a year ago

@dave your key is a String rather then an Integer, hence the CCE. Use Integer as a key instead

David Over a year ago

@Reimeus fixed those problems. thanks. Although it produced another type of error - which I guess I'll post in a different question

fge · Accepted Answer · 2013-06-14 15:14:51Z

6

   char[] words = new char[2];
   words[0] = 'a';
   words[1] = 'b';
   words[2] = 'c'; <-- HERE

You create a two elements array but put three items in it.

Arrays in Java have a fixed size which cannot be modified once they are initialized.

And then:

String value=(String)m.getValue();

This won't work: a char[] is not a String!

You have to:

String value = new String((char[]) m.getValue());

But you should you your map's .entrySet(), really.

answered Jun 14, 2013 at 15:14

fge

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Comments

thejh · Accepted Answer · 2013-06-14 15:16:15Z

3

new char[2] does not mean "make a new array with indexes that go up to 2". It means "make a new array that can hold 2 values", and as array indexes start at 0, the indexes go from 0 to 1.

answered Jun 14, 2013 at 15:16

thejh

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Comments

Bourne · Accepted Answer · 2013-06-14 15:15:35Z

1

words[2] is the culprit here! The array words is or size 2. So you can only have Words[0] and words[1]

answered Jun 14, 2013 at 15:15

Bourne

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Comments

arshajii · Accepted Answer · 2013-06-14 15:16:29Z

1

The integer argument used when we create a new array is not the highest index that should be available in that array but rather the actual size of the array. Therefore, as others have said, you would want

char[] words = new char[3];

to create an array capable of holding three elements.

answered Jun 14, 2013 at 15:16

arshajii

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