Thread: String Index Out of range

Hii, this code is giving string index out of range exception

import java.net.*;
import java.io.*;
import javax.swing.*;
import java.util.Scanner;
public class EraseClient{
public static void main(String args[]){
try {
	String s = JOptionPane.showInputDialog("Enter the string message");
	int len=s.length();
	System.out.println("msg size is ="+len);
	String block=JOptionPane.showInputDialog("enter the block size as a prime number");
	int j,result;
	boolean flag=false;	 
	int b=Integer.parseInt(block);
 
	while(flag==false)
	{
	     for (j=2; j< b ;j++ )
		{
	     result = b%j;
 
	if(result==0)
	{
	flag=false;
	break;
	}
	else{flag=true;}
 
	  }
	if (flag==false)
	{
	String str=JOptionPane.showInputDialog("Reenter the block size as a prime number between 1-100");
		  b=Integer.parseInt(str);
 
 
	    }
	}
	System.out.println("Block Size is=" +b);
	int num=  (len/b);
	String rep=JOptionPane.showInputDialog("enter the replication factor");
	int r=Integer.parseInt(rep);
	System.out.println(" replication factor is ="+ r);
	int noOfBlocks;
	if(len%b==0)
		{		
		noOfBlocks=len/b;
		}
	else
		{
		noOfBlocks=(len/b)+1;
		int a=b-(len%b);
		for(int i=0;i<a;i++)
			{s=s+"*";}
		}
System.out.println("Message string after adding dummy bits");
System.out.println(s);
System.out.println("System will generate total number of blocks=" +noOfBlocks );
int l=0;
String[] s3 = new String[100];
for(int i=1;i<=noOfBlocks;i++)
		{
System.out.println("block number"+ i +":"+s.substring(l,l+b));
l=i*b;
		}
for(int k=1;k<=noOfBlocks;k++)
 
		{
	System.out.println("replication of block"+ k + ":");
		int value=97;		
	for(int i=1;i<=r;i++)
		{
 
 
 
		s3[k] = new String(s.substring(l,l+b));
		String strk = Integer.toString(k);
		String message= strk+ (char)value +" " +s3[k];
			value=value+1;
		System.out.println(message);
		}
		}
}
 
	catch(Exception e)
	{
		System.out.println(e);
	}
		}
}