need help about reading numbers inside file

Question

• First I create a txt file (a.txt) -- DONE
• create 10 random number from - to ( like from 5 -10 ) --DONE
• I write this number in txt file --DONE
• I want to check its written or not -- DONE

• Now I need to find: how many number, biggest, smallest, sum of numbers But I can not call that file and search in the file (a.txt). I am just sending last part. Other parts work. I need some help to understand. It is also inside another method. not main

  Scanner keyboard = new Scanner(System.in);
  boolean again = true;
  int max = Integer.MIN_VALUE;
  int min = Integer.MAX_VALUE;
  int a = 0;
  int count = 0;
  
  System.out.println("Enter the filename to write into all analysis: ");
  outputFileName = keyboard.nextLine();
  
  File file2 = new File(outputFileName);
  if (file2.exists()) {
      System.out.println("The file " + outputFileName +
          " already exists. Will re-write its content");
  }
  
  
  try {
      PrintWriter yaz = new PrintWriter(file2);
  
      // formulas here. created file a.txt  need to search into that file biggest smallest and sum of numbers
  
      yaz.println("Numeric data file name: " + inputFileName);
      yaz.println("Number of integer: " + numLines);
      yaz.println("The total of all integers in file: " + numLines); //fornow
      yaz.println("The largest integer in the set: " + max);
      yaz.println("The smallest integer in the set " + min);
  
      yaz.close();
      System.out.println("Data written to the file.");
  } catch (Exception e) {
      System.out.printf("ERROR reading from file %s!\n", inputFileName);
      System.out.printf("ERROR Message: %s!\n", e.getMessage());
  
  }
  

Answer 1

You need to read the file into memory. One way to do that is to move the text of the file into a String.

This post will help you: Reading a plain text file in Java

Here's the relevant code:

try(BufferedReader br = new BufferedReader(new FileReader("file.txt"))) {
    StringBuilder sb = new StringBuilder();
    String line = br.readLine();

    while (line != null) {
        sb.append(line);
        sb.append(System.lineSeparator());
        line = br.readLine();
    } 
    String everything = sb.toString();
} 

Answer 2

So you want a code to read a text file and give you the biggest, smallest and the average. You can use Scanner class for that and use hasNextInt() to find integers

        File f = new File("F:/some_text_file.txt"); // input your text file here
    if(f.exists()){
        try{    
            Scanner sc = new Scanner(f);
            int max = Integer.MIN_VALUE;
             int min = Integer.MAX_VALUE;
             int temp=0, i=0;
             double sum=0;
            while(sc.hasNextInt()){
                temp = sc.nextInt();
                if(temp>max) max = temp;
                if(temp<min) min =temp;
                sum+=(double) temp;
                i++;

            }
            System.out.println("average : " +sum/i);    
            System.out.println("large : "+max);
            System.out.println("small :"+min);
            sc.close();
        }catch(Exception e){
            e.printStackTrace();
        }       
    }

See if this works