在 Java 中，如何访问整数数组的 ArrayList

Question

Here's my code:

    // create an arraylist of type integer array
    ArrayList<int[]> timesTables = new ArrayList<>();

    // add data
    timesTables.add(new int[]{42, 17, 81});
    timesTables.add(new int[]{1, 2, 3});
    timesTables.add(new int[]{1000, 2000, 3000});

    // this does not work        
    Log.i("Status ", timesTables.get((0)[0]).toString());

I know the mistake here has something to do with the way I'm attempting to reference the data with (0)[0], but I can't figure out the correct syntax. I know that this works:

    Log.i("Status ", timesTables.get(0).toString());

But this only gives the array address (I think) and not the values of an array nor an individual value in one array, which is what I'm attempting.

Secondary question: I attempted to look at the documentation to answer this question myself, but as a beginner, I was unsure where to look. I didn't know which website I should be using or which piece of code I should be looking up (get, int[], etc..).

Thanks in advance for your help.

Answer 1

What you are creating is a list of int primitive arrays .

So, use the List's get() method to obtain by index which array to use, followed by the index of the target entry in the obtained array.

timesTables.get(0)[0]

You can't use toString as the value you wish to print is an int primitive type .

So for your specific question you can do as next:

 Log.i("Status", Integer.toString(timesTables.get(0)[0]));

To clarify a bit your doubts, in a more verbose way, the above is the same as doing next:

 int[] array = timesTables.get(0); // Get by index an array from the list
 int value = array[0]; // Get by index an int value from the obtained array
 Log.i("Status", Integer.toString(value));

Answer 2

You can't put an index of nothing, so you should write the name of the array you're trying to access when you write (0) .

// create an arraylist of type integer array
    ArrayList<int[]> timesTables = new ArrayList<>();

    // add data
    timesTables.add(new int[]{42, 17, 81});
    timesTables.add(new int[]{1, 2, 3});
    timesTables.add(new int[]{1000, 2000, 3000});

    // this does not work        
    Log.i("Status ", Integer.toString(timesTables.get(0)[0]));

Answer 3

You are correct in that this prints the object reference of the int array.

Log.i("Status ", timesTables.get(0).toString());

If you want to print the contents of the array instead, use Arrays.toString(...) , eg:

Log.i("Status ", Arrays.toString(timesTables.get(0)));