Help me in solving AOJ19 problem

My issue

i want solution i tried many times please provide me accurate solution

My code

import java.util.*;
import java.text.DecimalFormat;

class Codechef
	public static void main (String[] args)
	     DecimalFormat decimalFormat = new DecimalFormat("0.0000000000");

		Scanner read = new Scanner(;
		int t = read.nextInt();
		for(int i=0; i<t; i++)
		    ArrayList<Integer> face = new ArrayList<Integer>();
		    int n = read.nextInt();
		    int a = read.nextInt();
		    int b = read.nextInt();
		    // Update the code below to solve this problem

		  //  ArrayList<Integer> a=new ArrayList<Integer>();
		    for(int j=0;j<n;j++)
		     int c1=1;
		     for(int k=0;k<n-1;k++)
		         if(face.get(k)==a && face.get(k+1)==b)
		          // for(int j=0 , k=n-1; j<=n-1 && k>=1 ;j++,k--)
		          // System.out.println(j+" "+k);
		       System.out.println( decimalFormat.format((double)(c1*c1)/(n*n)));

Learning course: Solve Programming problems using Java
Problem Link: CodeChef: Practical coding for everyone