how do i detect a double line break in a data file-CodePudding

I have a data file that consists of a calorie count. the calorie count it separated by each elf that owns it and how many calories are in each fruit. so this represents 3 elves

all the numbers next to each other are the same elf. the separated ones are seperate.

i tried to detect the double line break like so

import java.util.*;
import java.io.*;
public class Main 
{
  public static void main(String [] args) throws FileNotFoundException
  {
    int[] elf = new int[100000];
    int cnt = 0;
    Scanner input = new Scanner(new File("Elf.dat"));
    
    while(input.hasNext())
    {
      elf[cnt]  = input.nextInt();
      if (input.next().equals("\n\n"));
      {
        cnt  ;
      }
    }
    int big = elf[0];
    for (int lcv = 0; lcv < elf.length; lcv  )
      {
        if (big < elf[lcv])
        {
          big = elf[lcv];
        }
      }
    System.out.println(big);
  }
}

I'm trying this to detect the double line break

if (input.next().equals("\n\n"));

but its giving me errors. how would i detect it

CodePudding user response：

Here is another alternative way to do this sort of thing. read comments in code:

public static void main(String[] args) throws FileNotFoundException {
    List<Integer> elfSums;  // Can grow dynamically whereas an Array can not.
    int sum;
    // 'Try With Resources' used here to auto close the reader and free resources.
    try (Scanner input = new Scanner(new File("Elf.dat"))) {
        elfSums = new ArrayList<>(); 
        String line;
        sum = 0;
        while (input.hasNextLine()) {
            line =  input.nextLine();
            if (line.trim().isEmpty()) {
                elfSums.add(sum);
                sum = 0;  // Reset sum to 0 (new elf comming up)
            }
            // Does the line contain a string representation of a integer numerical value?
            if (line.matches("\\d ")) {
                // Yes...add to current sum value.
                sum  = Integer.parseInt(line);
            }
        }
    }
    if (sum > 0) {
        elfSums.add(sum);
    }
    
    // Convert List to int[] Array (There are shorter ways to do this)
    int[] elf = new int[elfSums.size()];
    for (int i = 0; i < elfSums.size(); i  ) {
        elf[i] = elfSums.get(i);
        // For the heck of it, display the total sum for this current Elf
        System.out.println("Elf #"   (i 1)   " Sum: -> "   elf[i]);
    }
    
    /* The elf[] int array now holds the data you need WITHOUT 
       all those empty elements with the array.        */
    
}

CodePudding user response：

Welcome to Advent of Code 22.

As a good rule, never mix nextXXX methods with any other next.

To break up the Blocks you have 2 good options:

Read line by line and fill a new list when you encounter a empty/blank line
Read the whole text fully, then split by the \n\n Combination