F - Prime Path POJ - 3126 JAVA

import java.math.BigInteger;
import java.util.ArrayDeque;
import java.util.Arrays;
import java.util.HashSet;
import java.util.LinkedList;
import java.util.Queue;
import java.util.Scanner;
import java.util.Set;

import javax.swing.text.GapContent;

public class Main
{

	public static void main(String args[])
	{
		Scanner sc = new Scanner(System.in);
		while (sc.hasNext())
		{
			int a = sc.nextInt();
			while (a-- > 0)
			{
				int tt = sc.nextInt();
				int yy = sc.nextInt();
				boolean x[] = new boolean[10005];
				int y[] = new int[10005];
				es(x, y);

				Queue<sb> queue = new LinkedList<sb>();
				int f[] = new int[4];

				f[0] = tt / 1000;
				f[1] = (tt / 100) % 10;
				f[2] = (tt % 100) / 10;
				f[3] = tt % 10;

				sb xx = new sb(f, 0, tt, "");
				y[tt] = 0;
				queue.offer(xx);
				boolean hh = false;

				while (!queue.isEmpty())
				{
					sb nodeSb = queue.poll();
					int g[] = nodeSb.x;
					int gg = nodeSb.step;
					StringBuilder ok = new StringBuilder();
					for (int i = 0; i < g.length; i++)
					{
						ok.append(g[i]);
					}
					int ssb = Integer.valueOf(ok.toString());
					if (ssb == yy)
					{
						hh = true;
						System.out.println(gg);
					//	System.out.println(nodeSb.f);
						;
						break;
					}
					int nb[] = new int[4];
					for (int i = 0; i < 4; i++)
					{
						for (int j = 0; j < nb.length; j++)
						{
							nb[j] = g[j];
						}
						for (int j = 0; j < 10; j++)
						{
							nb[i] = j;

							StringBuilder nnb = new StringBuilder();
							for (int k = 0; k < nb.length; k++)
							{

								nnb.append(nb[k]);
							}
							int ip = Integer.valueOf(nnb.toString());
							if (y[ip] == 1 && ip >= 1000)
							{

								sb vv = new sb(nb, gg + 1, ip, nodeSb.f);
								queue.offer(vv);
								y[ip] = 0;
							}
						}
					}

				}
				if (hh == false)
				{
					System.out.println("impossible");
				}

			}

		}
	}

	public static void es(boolean x[], int y[])
	{
		int xx = 0;
		for (int i = 2; i < x.length; i++)
		{

			if (x[i] == false)
			{
				y[i] = 1;

			}
			for (int j = 1; j < y.length && (i * j < y.length); j++)
			{
				x[j * i] = true;
			}
		}

	}

}

class sb
{
	int step;
	int x[] = new int[4];
	int ip;
	String f = "";

	public sb(int x[], int step, int ip, String sb)
	{
		for (int i = 0; i < x.length; i++)
		{
			this.x[i] = x[i];
		}
		this.step = step;
		this.f = sb + " " + ip;

	}

}