Adjacency-list-representation-of-graph-in-java.java

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;


class Edge {
	int src;
	int dest;
	public Edge(int src,int dest) {
		this.src = src;
		this.dest = dest;
	}
}


class Graph {
	
	private ArrayList<ArrayList<Integer>> graph;

	public Graph() {

		// List of graph edges as per above diagram
		List<Edge> edges = Arrays.asList(
							new Edge(1, 0), 
							new Edge(2,1),
							new Edge(3,4), 
							new Edge(4,0)
						);
		
		graph = new ArrayList<ArrayList<Integer>>();

		for(int i=0;i<4;i++) {
			graph.add(i,new ArrayList<Integer>());
		}
		
		// adding the vertex to the graph
		for(int i=0;i<edges.size();i++) {
			Edge e = edges.get(i);
			graph.get(e.src).add(e.dest);
		}

	}
	
}