2d array list in java code example

Example 1: 2d arraylist in java

int vertexCount = 3;
ArrayList<ArrayList<Integer>> graph = new ArrayList<>(vertexCount);
//Next, we'll initialize each element of ArrayList with another ArrayList:

for(int i=0; i < vertexCount; i++) {
    graph.add(new ArrayList());
}

Example 2: 2d array java

//Length
int[][]arr= new int [filas][columnas];
arr.length=filas;

        int[][] a = {
            {1, 2, 3}, 
            {4, 5, 6, 9}, 
            {7}, 
        };
      
        // calculate the length of each row
        System.out.println("Length of row 1: " + a[0].length);
        System.out.println("Length of row 2: " + a[1].length);
        System.out.println("Length of row 3: " + a[2].length);
    }

Example 3: creating a 2d arraylist in java

List<List<String>> listOfLists = new ArrayList<List<String>>(size); 
for(int i=0; i<size; i++) {
	listOfLists.add(new ArrayList<String>());
}