i dont know whats wrong with this program...the compiler compiles the program but when i run it it shows:
johnrambo@ubuntu:~/Desktop$ java lora
Exception in thread "main" java.lang.NumberFormatException: null
at java.lang.Integer.parseInt(Integer.java:443)
at lunda.l2read(lora.java:24)
at lora.main(lora.java:124)

class lunda{


	String[] la=new String[2048];
	String[] lb=new String[2048];
	int[] lvalid_a=new int[2048];
	int[] lvalid_b=new int[2048];
	int[] lage_a=new int[2048];
	int[] lage_b=new int[2048];
	int lhit=0;
	int lmiss=0;
	String s1;
	String s2;
	int lindex;
	String ls1;
	String ls2;
	
	String ruba;
	public String l2read(String s)
	{
		String ls1=s.substring(0,14);
		String ls2=s.substring(14,25);
		int lindex=Integer.parseInt(s2,2);


		for(int i=0;i<2048;i++)
		{
			lvalid_a[i]=0;                                                  //initialising array ot 0//
			lvalid_b[i]=0;
		}


		if(lvalid_a[lindex]==0&& lvalid_b[lindex]==0)
		{
			la[lindex]=ls1;

			lvalid_a[lindex]=1;
			lage_a[lindex]=1;
			String ruba="0";

		}
		if(lvalid_a[lindex]==0&& lvalid_b[lindex]==1)
		{
			if(ls1==lb[lindex])
			{
				lage_b[lindex]++;
				String ruba="1";

			}	
			else
			{
				la[lindex]=s1;

				lvalid_a[lindex]=1;
				String ruba="0";

			}
		}
		if(lvalid_a[lindex]==0&& lvalid_b[lindex]==1)
		{
			if(ls1==la[lindex])
			{
				lage_a[lindex]++;
				String ruba="1";

			}	
			else
			{
				lb[lindex]=s1;	

				lvalid_b[lindex]++;
				String ruba="0";

			}
		}

		if(lvalid_a[lindex]==1&&lvalid_b[lindex]==1)
		{
		
		if(ls1==la[lindex])
		{
			lage_a[lindex]++;
			String ruba="1";

		}	

		else if(ls1==lb[lindex])
		{
			lage_b[lindex]++;
			String ruba="1";

		}

		else
		{

			if(lage_a[lindex]>=lage_b[lindex])
			{
				la[lindex]=ls1;
				lage_a[lindex]=1;
				lage_b[lindex]++;
			}
			else
			{
				lb[lindex]=s1;
				lage_b[lindex]=1;
				lage_a[lindex]++;
			}
				String ruba="0";
		}
		}

		return ruba;
	}
	}
	public class lora
{
	public static void main(String[] args) throws Exception
	{
		String s;
		s="10101010101000000011111001100111";
		lunda x=new lunda();
		String g=x.l2read(s);
		System.out.println(g);
	}
}

according the error message you're trying to parse a null-value (a variable in which you haven't stored a value yet) into an integer.

you 've stored a value in ls2, not in s2, which you are trying to parse.

ohhhh such a silly mistake on my side. thanks for your help.:)

and ... how is this post adding anything?

my post was late by 2 minutes, hope you understand =.=

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