Lempel-Ziv-Welch compression algorithm program in Java

import java.io.*;

public class LZWCompression
{
 String input="",prefix="",word;
 char arr[],ch;
 int d_index=0,i,codeword,match;
 String dict[];
   
 public int in_dictionary(String str)
 {
  int i;
  for(i=1;i<=d_index;i++)
   if(str.equals(dict[i]))
   {
    return i;
   } 
  return -999;
 }
 
 public LZWCompression()
 {
  try
     {
   System.out.print("Enter any String :");
      BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
      input=br.readLine();
      arr=input.toCharArray();
   
         dict=new String[input.length()];
         
         System.out.println("Encoded Output :");
      i=0;
      while(i<input.length())
      {
          ch=arr[i];
       word=prefix+ch;
       
       if(in_dictionary(word)!=-999)
       {
        prefix=word;
       }
       else
       {
        if(prefix.equals(""))
         codeword=0;
        else
            codeword=in_dictionary(prefix);
        System.out.print(codeword);
        System.out.println(" :"+ch);
        dict[++d_index]=word;
        prefix="";
       }
       i++;
      }
      if(!prefix.equals(""))
      {
       codeword=in_dictionary(prefix);
       System.out.print(codeword);
    System.out.println(" :"+" ");
      }
         System.out.println("Dictionary Contents :");
      for(i=1;i<=d_index;i++)
      {
       System.out.print(i + ":");
          System.out.println(dict[i]);
      }
     }
     catch(Exception ex)
     {
      ex.printStackTrace();
     }
 }
    public static void main(String args[])
    {
     new LZWCompression();  
    }
}