Breadth First Search (BFS) in java

Breadth-First Search:

Breadth-First Search (BFS) is a searching algorithm that searches the destination from root or source and explores all the neighbor nodes first, before moving to the next level neighbors. The animation will make this more clear.

To learn Breadth-First Search (BFS) more deeply, you can download Breadth-First Search in the PowerPoint slide.

The following code is to implement Breadth-First Search (BFS) in java
:

import java.io.*;
import java.util.*;
 public class Bfs {
 public static int WHITE=1,GRAY=2,BLACK=3,inf=31000,NIL=-1;
 public int num_v,num_e;
 public Queue<integer>q=new LinkedList<integer>();
 public int adj[][]=new int[20][20];
 public int color[]=new int[20];
 public int d[]=new int[20];
 public int p[]=new int[20];
  public void initialization() {
     int k,j;
     for(k=0;k<20;k++)
     {
         for(j=0;j<20;j++)
         {
             adj[k][j]=0;
         }
     }
 }
 public void build_adj_matrix() {
     int i,a,b;
     Scanner g=new Scanner(System.in);
     num_v=g.nextInt();
     num_e=g.nextInt();
     for(i=1;i<=num_e;i++)
     {
         a=g.nextInt();
         b=g.nextInt();
         adj[a][b]=1;
         adj[b][a]=1;
     }
 }
 public void BFS(int s) {
     int i,u,v;
     for(i=1;i<=num_v;i++)
     {
         color[i]=WHITE;
         d[i]=inf;
         p[i]=NIL;
     }
     color[s]=GRAY;
     d[s]=0;
     p[s]=NIL;
     q.add(s);
     while(!q.isEmpty())
     {
         u=q.peek();
         q.poll();
         for(v=1;v<=num_v;v++)
         {
             if(adj[u][v]==1)
             {
                 if(color[v]==WHITE)
                 {
                     color[v]=GRAY;
                     d[v]=d[u]+1;
                     p[v]=u;
                     q.add(v);
                 }
             }
         }
         color[u]=BLACK;
     }
 }
 public void distance_output() {
     int i;
     System.out.println("Shortest path from Source vertex");
     for(i=1;i<=num_v;i++)
     {
         System.out.println("to node "+i+" is "+d[i]);
     }
 }
  public void path_print(int s, int v) {
     if(v==s)
         System.out.print(s);
     else if(p[v]==NIL)
         System.out.println("No path from "+s+" to "+v+"exists");
     else
     {
         path_print(s,p[v]);
         System.out.print(v);
     }
 }
      /**      * @param args the command line arguments      */
     public static void main(String[] args) {
         // TODO code application logic here
         int source, destination;
         Bfs g=new Bfs();
         g.initialization();
         g.build_adj_matrix();
         Scanner m=new Scanner(System.in);
         source=m.nextInt();
         //Scanner 
n=new Scanner(System.in);
         destination=m.nextInt();
         g.BFS(source);
         g.distance_output();
         g.path_print(source, destination);
     }
 }

You can practice Breadth-First Search (BFS) from here.
For more algorithm implementation, visit here...

Breadth First Search (BFS) in java