Create an array of ArrayList elements

Question

I want to create an array that contains ArrayList elements.

I\'ve tried

ArrayList name[] = new ArrayList()[];
         


        

Answer 1

I know this is a bit old but I am going to respond to this anyway for future views.

If you really want an ArrayList[] structure, you can simply create a class that extends ArrayList and make an array of that class:

public class StringArrayList extends ArrayList{}

And in your implementation:

ArrayList name[] = new StringArrayList[9];

Here is a sample:

package testspace.arrays;

import java.util.List;

public class TestStringArray {

    public static void main(String[] args) {
        List[] arr = new StringArrayList[10];
        for(int i = 0; i < arr.length; i++){
            // CANNOT use generic 'new ArrayList()'
            arr[i] = new StringArrayList(); 
            for(int j = 0; j < arr.length; j++){
                arr[i].add("list item #(" + j + "|" + i + ")");
            }
        }

        StringBuilder sb = new StringBuilder();
        for(final List list : arr){
            for(final String str : list){
                sb.append(str + " ");
            }
            sb.append("\n");
        }
        System.out.println(sb.toString());
    }

}

NOTE You will get a runtime error if you use this instead : arr[i] = new ArrayList()