如何访问对象数组的数组元素？

Question

public class arrayOfArrays{ 
       public Object[] array1;
       public int size;           

       arrayOfArrays(){
            array1 = new Object[10];
            array1[0] = new arrayOfInts();
   }
}

class arrayOfInts{
      public Integer[] array2;
      public int size;

      arrayOfInts(){
         array2 = new Integer[10]; 
    }
}

I am trying to create a 2d array of some sort that has varying length of the arrays that are contained within it. For example, array1[0] will have an array of Ints that has a length of 3. array1[1] will have an array of Ints of length 5. and so on.

If I want to access elements of array2 from within my arrayOfArrays class. How would I accomplish that?

I have tried: array1[this.size].array2[size] = x; However, this gives me an error. Do I need to cast the second array? Any help would be appreciated. Cheers

Answer 1

I don't really understand why you creates those classes.

You can simply store any kind of things in an Object array.

Object[] array1 = new Object[ 5 ];
Random rd = new Random();

for( int i = 0; i<5; i++ )
  array1[ i ] = new int[ rd.nextInt( 5 ) + 1 ];

System.out.println( Arrays.deepToString( array1 ) );

Here i've created 5 int array with random size.

The problem is that you have to cast the result of array1[i] into an int[] as far as you define it as an Object[]

int[] o1 = ( int[] ) array1[ 1 ];
System.out.println( o1 );

A simpler solution would probably be to use a list on Integer arrays. This way there is non needs to cast.

List<Integer[]> list1 = new ArrayList<>();

for( int i = 0; i<5; i++ )
  list1.add( new Integer[ rd.nextInt( 5 ) + 1 ] );

for( Integer[] array : list1 )
  for( int i=0;i<array.length;i++)
    array[i] = rd.nextInt( 100 );

System.out.println(  Arrays.deepToString( list1.toArray() ) );