Need help for a doubt..Using BufferedReader.

[Ishani Mehta]

Hello,

Can anyone please help me in this? I am doing some practice problems. Suppose user enters the value like this:
2
1 7
2 8
//null line
and from this line onwards, i want to display output.

I have store value of 2 using, BufferedReader br =new BufferedReader(new InputStreamReader(System.in));
String[] input=br.readLine().split(" ");
int n1=Integer.parseInt(input[index]);
int n2=Integer.parseInt(input[index+1]);
//index=0;
index=index+2;
I want to put here a condition that when that null line comes, all the above lines before that null and after that first line (2 is written over there), I want to put all those values in an array. want to put a condition for that. if i write br.readline()!=null then it doesnt work. can you please tell me whats that condition should be inserted before n1's initialization??

Thanks

[Swastik Dey]

Even if the user does not enter anything , but after pressing enter the input does not remain null, but the length of the input is 0, so probably you need to check for the length

 
BufferedReader br =new BufferedReader(new InputStreamReader(System.in));
		String data=null;
		while(true){
			data=br.readLine();
			if(data.length()==0){
				break;
			}
			//do what you want to do with data
		}
	}
 

[Rob Spoor]

Swastik Dey wrote:

if(data.length()==0){ 

Please change that into

if (data == null || data.length() == 0)

If you don't you will get a certain NullPointerException if all lines have been read.

[Swastik Dey]

Thanks,

I should have included that == null check too.

[Ishani Mehta]

Thanks for your replies.

But the problem is:

2 // No. of lines
1 6 //diff. values.
5 9
//Empty Line
7 // Sum of 1 and 6
14 // 5+9

So first I want to store 2 in one variable
then 1 and 6 in n1[0] and n1[1]
after that 5 and 9 in n1[2] and n1[3]
after that an empty line
and from line 5 onwards, output should be displayed in separate lines.

I have used while(true){ ...... //code........} but it goes in continuous loop.

[Ishani Mehta]

Sorry..

--------------------------------------------
then 1 and 6 in n1[0] and n1[1]
after that 5 and 9 in n1[2] and n1[3]
---------------------------------------------

here input[0] and input[1] instead of n1..

[Swastik Dey]

So probably you need two conditions here, either the maximum number of lines have been entered by the user or the users enters a blank line in between

  

BufferedReader br =new BufferedReader(new InputStreamReader(System.in));
		String data=null;
		int arr[][];
		System.out.print("Enter number of lines:");
		int size=Integer.parseInt(br.readLine());
		arr=new int[size][2];
		for(int x=0;x<size;x++){ //we execute the loop for maximum number of lines
		     System.out.print("Enter number for row "+x);
			 data=br.readLine();
			 if(data==null || data.length()==0){ //but if we get an empty line we forcefully break the loop
			 	break;
			 }
			 String[] input=data.split(" ");
			 arr[x][0]=Integer.parseInt(input[0]);
			 arr[x][1]=Integer.parseInt(input[1]);
		}


		for(int x=0;x<size;x++){
			System.out.println(arr[x][0]+arr[x][1]);
		}
  

Let us know if I am getting wrong

[Ishani Mehta]

Thank you very much.

I have used two dimensional array..

Its working fine now.

Thanks