ArrayIndexOutofBounds/NullPointerException in Java

Question

I am a beginner here in Java. So my problem is I am trying to hide all photo components of my window and make some others appear. But the problem is it always throws Exception in thread "AWT-EventQueue-0" java.lang.ArrayIndexOutOfBoundsException: 10 everytime I select an Item using JComboBox.

Here is the code block for the error:

for (cnt1=0; cnt1<10; cnt1++);
        {
            labels1[cnt1].setVisible(true);
        }

        for (cnt2=0; cnt2<10; cnt2++);
        {
            labels2[cnt2].setVisible(false);
        }


        for (cnt3=0; cnt1<10; cnt3++);
        {
            labels3[cnt3].setVisible(false);
        }

        for (cnt4=0; cnt4<10; cnt4++);
        {
            labels4[cnt4].setVisible(false);
        }

        for (cnt5=0; cnt5<10; cnt5++);
        {
            labels5[cnt5].setVisible(false);
        }

can you tell me what seems to be the problem here. I will post the whole code if you requests for it. Thank you in advance.

Edit: I have fixed the errors in my array, but this time,. the compiler gave me this error:

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException

By the way, this is a snippet of the declaration my arrays:

String iconFiles1[] = {"Articuno.png", "Blastoise.png", "Charizard.png", "Kabutops.png", "Mewtwo.png", "Moltres.png", "Omastar.jpg", "Pikachu.jpg", "Venusaur.png", "Zapdos.png"};
String Jlabels1[] = {"Articuno", "Blastoise", "Charizard", "Kabutops", "Mewtwo", "Moltres", "Omastar", "Pikachu", "Venusaur", "Zapdos"};
ImageIcon icons1[] = new ImageIcon[iconFiles1.length];
JLabel labels1[] = new JLabel[Jlabels1.length];

and this is its assignment in the GUI:

for (int cnt1=0; cnt1<labels1.length; cnt1++)
        {
            labels1[cnt1].setVisible(true);
        }

am I doing it right? Answers are appreciated. Again. Thank you.

The semicolon in the first line looks wrong. What is in the labels*-Arrays? — zero0
– zero0, Commented Jul 7, 2013 at 9:18
for better help sooner post an SSCCE, short, runnable, compilable, generating a.m. exception — mKorbel
– mKorbel, Commented Jul 7, 2013 at 9:18
seems u have labels1 upto [9] ... but u r trying to access labels1[10]... ur cnt1 = 10 after the first for loop — Michael Shrestha
– Michael Shrestha, Commented Jul 7, 2013 at 9:20

Steve P. · Accepted Answer · 2013-07-07 09:33:08Z

2

You appear to have incorrect variables in at least one of your for loops (as several other posters have already pointed out).

Nonetheless, the reason you're getting an ArrayIndexOutOfBoundsException is because you have semicolons after all of your for loops, thereby making them do nothing but increment your counter variables. The variables that you're incrementing in your for loops are not locally declared in the for loops themselves, so their scope is whatever function you're currently in (aka they exist outside of the for loops). So when the loops finish incrementing, your counters will be too large (10 in this case)---> hence the ArrayIndexOutOfBoundsException: 10.

edited Jul 7, 2013 at 9:33

answered Jul 7, 2013 at 9:22

Steve P.

14.7k9 gold badges46 silver badges74 bronze badges

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

2 Comments

Steve P. Over a year ago

@SageTheGreat This completely answers your question.

Steve P. Over a year ago

@SageTheGreat Also, since you're new, you should take the tour.

BackSlash · Accepted Answer · 2013-07-07 09:26:10Z

0

First, you have a semicolon after every for statement, which basically tells the compiler to loop without executing code.

for (cnt1=0; cnt1<10; cnt1++);
{
    labels1[cnt1].setVisible(true);
}

Must become

for (cnt1=0; cnt1<10; cnt1++)
{
    labels1[cnt1].setVisible(true);
}

And so on for every loop.

Second: I think this

for(cnt3=0; cnt1<10; cnt3++)

Should become

for(cnt3=0; cnt3<10; cnt3++)

answered Jul 7, 2013 at 9:26

BackSlash

22.3k25 gold badges103 silver badges143 bronze badges

Comments

Steve P. · Accepted Answer · 2013-07-07 09:29:25Z

0

for (cnt1=0; cnt1<10; cnt1++);
  {
     labels1[cnt1].setVisible(true);
  }

You have put semi-colon in first statement. So your loop is iterating 10 times without doing nothing. Value cnt1 when we get out of loop is 11.

Then you try to set 11th element of array labels1[cnt1].setVisible(true);

As you may not be having 11 elements in array you are getting IndexOutofBound. Do like this :

for (cnt1=0; cnt1<10; cnt1++)
  {
     labels1[cnt1].setVisible(true);
  }

edited Jul 7, 2013 at 9:29

Steve P.

14.7k9 gold badges46 silver badges74 bronze badges

answered Jul 7, 2013 at 9:27

shashankaholic

4,1223 gold badges27 silver badges28 bronze badges

Comments

Steve P. · Accepted Answer · 2013-07-07 09:30:40Z

0

I see three things that don't seem to work in your code:

for (cnt1=0; cnt1<10; cnt1++); and all other lines should not end with a semi-colon
for (cnt3=0; cnt1<10; cnt3++); the reference to cnt1 in this line should probably be to cnt3
In general, you should reference the size of your Array, such as:

for (int i = 0; i < labels.length; i++)

This way you are sure you won't reference any value out of the Array's bounds.

edited Jul 7, 2013 at 9:30

Steve P.

14.7k9 gold badges46 silver badges74 bronze badges

answered Jul 7, 2013 at 9:25

Mena

48.6k11 gold badges90 silver badges110 bronze badges

Collectives™ on Stack Overflow

ArrayIndexOutofBounds/NullPointerException in Java

4 Answers 4

2 Comments

Comments

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

4 Answers 4

2 Comments

Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related