How to generate output file for given input file in java

Question

I am facing trouble to submit a code in a coding platform.

Problem Statement

A local musician is putting on a concert to raise money for charity. The concert will be held in the town hall, a spacious venue perfectly suited for such an event.

• There are r rows of seats, each containing exactly s seats.
• At most one person can sit on a single seat (that is, two people cannot share a seat).

There is a problem - the concert may have been overbooked! This means that if everybody who bought tickets comes to the concert, some of them might have to stand.

Now the musician has approached you, not for advice, but for the answer to the following question:

if everybody who bought tickets arrives and tries to find a seat, how many people will end up sitting, and how many people will be standing?

This is my program:

  package Prerequisite;
  import java.io.FileInputStream;
  import java.io.FileOutputStream;
  import java.io.PrintStream;
  import java.util.Scanner;

  public class Solution {
  static private  final String INPUT ="sitin.txt";   
  static private  final String OUTPUT ="sitout.txt";   
  public static void main(String[] args) {
    FileInputStream instream = null;  
    PrintStream outstream = null;  
      try  {  
          instream =  new  FileInputStream (INPUT);  
          outstream =  new  PrintStream ( new  FileOutputStream (OUTPUT));  
          System.setIn (instream);  
          System.setOut (outstream);  
      }  catch  (Exception e) {  
          System.err.println ( "Error Occurred." );  
      }
     Scanner sc=new Scanner(System.in);
     int r=sc.nextInt();
    int s=sc.nextInt();
    int ticket=sc.nextInt();
    if((r*s)>=ticket)
   {
   System.out.println(ticket+" "+0);
    }
  else
  {
    System.out.println(r*s+" "+(ticket-r*s));
  }
   }
     }

Input 7 12 100

Output 84 16

Answer 1

When I was a 16 years, I started programming with pseudo-code: structograms, a kind of visualization of logical flow. This may help to solve the decomposition by divide & conquer.

But first of all start defining your given inputs & expected output - call it your User-Interface (here: file-based)

Requirements: input/output interface

Supposed given Input

You are given a file with a line containing 3 records delimited by a space-character:

7 12 100

Above 3 records represent numbers which are read into variables as follows:

• 7 rows in the concert hall
• 12 seats in each row of the hall
• 100 tickets are sold in total for the concert

Expected Output

The program should write its output to a file. So that this file contains a single line with 2 records, i.e numbers delimited by space (similar to given input format). First the resulting total count of occupied seats. Second the remaining count of left over visitors that can't be seated and are standing. For example:

84 16

Decomposition into Pseudo code

I can't draw a structogram here. And for your task amd language (Java), I advise to start with a couple of comments. Just write down like a movie-plot with separate scenes (input, processing, output) what should happen. Like this:

// (1) read parameters (3 variables) from input (file):
   // open given input-file (sitin.txt)
   // read first line from file
   // close file
   String content = Files.readString(path, StandardCharsets.US_ASCII);
   // split the read line by delimiter space into 3 strings (e.g. array)
   // convert the 3 strings into number variables (e.g. rows, seats, tickets

//  (2) calculate maximum seats (capacity) and ticket-category distribution (seated VS standing):
  // do the math ..
  // return the results (e.g. an object with two fields/variables: totalSeated, totalStanding)

// (3) write results to output:
   // open given output-file (sitout.txt)
   // write 3 variables delimited by space to the file
   // close file

You now have divided the problem into 3 blocks. Each can be solved separately. Thus you can structure the program into 3 methods.

Why decomposition?

It might be your key to solve any problem. It's famously known and widely-practiced by following patterns/principles: separation of concerns, single responsibility principle or simply divide & conquer.

It has many benefits: isolated development and isolated testing. In this case: you can ask 3 separate questions on stackoverflow

For (1) I have already found an answer: File-Reading, I already inserted between comments above.

Which method is it you have tried to code? Where do you need our help: 1, 2 or 3?