Several alternatives to implementing list arrays in Java

In Java, it is forbidden List<Integer>a[] to define this list array structure.
However, there are some other ways to implement a list array.

First, use node to list Wrap it up.

public class GenericArray {static class Node {    public ArrayList<Integer> x;    public Node() {        x = new ArrayList<Integer>();    }}public static void main(String[] args) {    Node[] a = new Node[10];    for (int i = 0; i < a.length; i++) {        a[i] = new Node();        for (int j = 0; j < i; j++) {            a[i].x.add(j);        }    }    for (int i = 0; i < a.length; i++) {        for (int j = 0; j < a[i].x.size(); j++) {            System.out.print(a[i].x.get(j));        }        System.out.println();    }}}

Second, let node inherit List<Integer>

static class nodenode extends ArrayList<Integer> {}public static void main(String[] args) {    nodenode[] a = new nodenode[10];    for (int i = 0; i < 10; i++) {        a[i] = new nodenode();        for (int j = 0; j < i; j++) {            a[i].add(j);        }    }    for (int i = 0; i < a.length; i++) {        for (Integer j : a[i]) {            System.out.print(j + " ");        }        System.out.println();    }}

Third, the use List<List<>>Structure

Slightly

Several alternatives to implementing list arrays in Java