I write this code in Java but i get runtime error, waths wrong

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.Collections;


public class Main {
	static class Telefono implements Comparable<Telefono> {
		int reps = 1, number;

		public Telefono(int a) {
			this.number = a;
		}

		public int compareTo(Telefono obj) {
			return this.number - obj.number;
		}

		@Override
		public boolean equals(Object arg0) {

			return ((Telefono) (arg0)).number == this.number;
		}

	}

	static int pFormat(String a) {
		a = a.replaceAll(" ", "").replaceAll("-", "");
		a = a.replaceAll("[ABC]", "2");
		a = a.replaceAll("[DEF]", "3");
		a = a.replaceAll("[GHI]", "4");
		a = a.replaceAll("[JKL]", "5");
		a = a.replaceAll("[MNO]", "6");
		a = a.replaceAll("[PRS]", "7");
		a = a.replaceAll("[TUV]", "8");
		a = a.replaceAll("[WXY]", "9");
		return Integer.parseInt(a);
	}

	public static void main(String[] args) throws IOException {
		BufferedReader lc = new BufferedReader(new InputStreamReader(System.in));
		ArrayList<Telefono> tels = new ArrayList<Telefono>(100000);
		for (int i = Integer.parseInt(lc.readLine()); i > 0; i--) {
			String line = lc.readLine();
			Telefono tep = new Telefono(pFormat(line));
			int num = tels.indexOf(tep);
			if (num!=-1)
				tels.get(num).reps++;
			else tels.add(tep);
		}
		
		Collections.sort(tels);
		boolean dupl=false;
		for (Telefono telefono : tels) {
			
			if(telefono.reps>1){
				System.out.println((telefono.number/10000)+"-"+((String)(telefono.number+"")).substring(3)+" "+telefono.reps);
				dupl=true;
			}
				
		}
		if (!dupl)
			System.out.println("No duplicates.");
	}
}

• Carefully read F.A.Qs (1914) palmtenor 2008-07-28 11:36:22