traversing a 2-dimensional array in java

Question

i watch in a tutorial that i can traverse an array of object in this way:

     Animals[] an = new Animals[2];

         for (Animals a:an){
                 .
                 .
         }

But now i want to traverse a 2 dimensional array and when i use this code i have a problem(says:incompatible types required:appl1.Animals foundLappl1.Animals[]). when i use this code

   Animals[][] an = new Animals[2][2];

      for (Animals a:an){
             .
             .
       }

Does anyone knows how can i overcome this problems. Thank you in advance for your help.

Jon Newmuis · Accepted Answer · 2012-01-29 22:22:45Z

You will need to use nested loops, as follows:

Animals[][] an = new Animals[2][2];

for (Animals[] inner : an) {
    for (Animals a : inner) {
        // Execute code on "Animals" object a
    }
}

Why does this work?

Look at your first example (reposted here for convenience):

Animals[] an = new Animals[2];

for (Animals a : an) {
    // Do stuff here.
}

This works because an is an array of Animals objects. The for loop iterates through each Animals object, performing some action on them one-by-one.

Now look at my answer posted above (again, reposted here for context):

Animals[][] an = new Animals[2][2];

for (Animals[] inner : an) {
    for (Animals a : inner) {
        // Execute code on "Animals" object a
    }
}

This works because an is an array of Animals[] objects. The first for loop iterates through each Animals[]. At that point, you have an array of Animals objects, so you can use the same solution as above: a single for loop to iterate through each of the Animals object and perform some action on them one-by-one.

Joni · Accepted Answer · 2012-01-29 22:16:05Z

4

A two-dimensional array is really an array of arrays. You need nested loops: the outer loop goes through the array of arrays, and the inner loop goes through the elements of each individual array.

Animals[][] ann = new Animals[2][2];

for (Animals[] an:ann){
    for (Animals a:an){
         .
         .
    }
}

edited Jan 29, 2012 at 22:16

answered Jan 29, 2012 at 22:14

Joni

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1 Comment

Louis Wasserman Over a year ago

This is correct. You can't do this with a single loop...not without difficulty.

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