如何使用文件中的特定列对排名列表进行排序并打印排序后的整个文件？

Question

Already done this but can't make it work.

Also tried to create another while ((line = br.readLine()) != null) {}, and placed the sort before it, but it won't read this while so it wouldnt print anithing.

The file looks like this:

    1-Fred-18-5-0

    2-luis-12-33-0

    3-Helder-23-10-0

And wanted it to print like this:

    2-luis-12-33-0

    3-Helder-23-10-0

    1-Fred-18-5-0

---

public static void lerRanking() throws IOException {
        File ficheiro = new File("jogadores.txt");

        BufferedReader br = new BufferedReader(new FileReader(ficheiro));
        List<Integer> jGanhos = new ArrayList<Integer>();
        int i = 0;
        String line;
        String texto = "";

        while ((line = br.readLine()) != null) {

            String[] col = line.split("-");
            int colunas = Integer.parseInt(col[3]);
            jGanhos.add(colunas);

            i++;
            if(i>=jGanhos.size()){
                Collections.sort(jGanhos);
                Collections.reverse(jGanhos);
                for (int j = 0; j < jGanhos.size(); j++) {
                    if(colunas == jGanhos.get(i)){
                        texto = texto + line + "\n";    
                    }
                }
            }
        }    
        PL(texto);
}

Answer 1

Make it step by step:

public static void lerRanking() throws IOException {
    File ficheiro = new File("jodagores.txt");

    // read file
    BufferedReader br = new BufferedReader(new FileReader(ficheiro));
    List<String> lines = new ArrayList<>();
    String line;
    while ((line = br.readLine()) != null) {
        lines.add(line);
    }

    // sort lines
    lines.sort(new Comparator<String>() {
        @Override
        public int compare(String s1, String s2) {
            // sort by 3rd column descending
            return Integer.parseInt(s2.split("-")[3]) - Integer.parseInt(s1.split("-")[3]);
        }
    });

    // concat lines
    String texto = "";
    for (String l : lines) {
        texto += l + "\n";
    }

    System.out.println(texto);

    // PL(texto);

}

Answer 2

The easiest way is to first create a class that will hold the data from your file provided your lines keep the same format

public class MyClass {

  private Integer column1;
  private String column2;
  private Integer column3;
  private Integer column4;
  private Integer column5;

  public MyClass(String data) {
    String[] cols = data.split("-");
    if (cols.length != 5) return;

    column1 = Integer.parseInt(cols[0]);
    column2 = cols[1];
    column3 = Integer.parseInt(cols[2]);
    column4 = Integer.parseInt(cols[3]);
    column5 = Integer.parseInt(cols[4]);
  }

  public synchronized final Integer getColumn1() {
    return column1;
  }

  public synchronized final String getColumn2() {
    return column2;
  }

  public synchronized final Integer getColumn3() {
    return column3;
  }

  public synchronized final Integer getColumn4() {
    return column4;
  }

  public synchronized final Integer getColumn5() {
    return column5;
  }

  @Override
  public String toString() {
    return String.format("%d-%s-%d-%d-%d", column1, column2, column3, column4, column5);
  }
}

Next you can get a list of your items like this:

public static List<MyClass> getLerRanking() throws IOException {
  List<MyClass> items = Files.readAllLines(Paths.get("jogadores.txt"))
    .stream()
    .filter(line -> !line.trim().isEmpty())
    .map(data -> new MyClass(data.trim()))
    .filter(data -> data.getColumn4() != null)
    .sorted((o1, o2) -> o2.getColumn4().compareTo(o1.getColumn4()))
    .collect(Collectors.toList());

  return items;
}

This will read your whole file, filter out any blank lines, then parse the data and convert it to MyClass .

It will then make sure that column4 isn't null in the converted objects.

Finally it will reverse sort the objects based off from the value in column 4 and create a list of those items.

To print the results you can do something like this

public static void main(String[] args) {
   List<MyClass> rankingList = getLerRanking();
   rankingList.forEach(item -> System.out.println(item));
}

Since we overrode the toString() method, it will print it out the object as it is displayed in the file.

Hope this helps.

Answer 3

Okay so first of all I thounk you should introduce a Java class (in my code this is ParsedObject ) to manage your objects.

Second it should implement the Comparable<ParsedObject> interface, so you can easily sort it from anywhere in the code (without passing a custom comparator each time).

Here is the full code:

import java.io.*;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

public class Main {

    public static void main(String[] args) throws IOException {
        lerRanking();
    }

    public static void lerRanking() throws IOException {
        File ficheiro = new File("jodagores.txt");
        // read lines to a list
        List<String> lines = readLines(ficheiro);
        // parse them to a list of objects
        List<ParsedObject> objects = ParsedObject.from(lines);
        // sort
        Collections.sort(objects);
        // print the output
        writeLines(objects);
    }

    public static List<String> readLines(File ficheiro) throws IOException {
        // read file line by line
        BufferedReader br = new BufferedReader(new FileReader(ficheiro));
        List<String> lines = new ArrayList<>();
        String line;
        while((line = br.readLine()) != null) {
            lines.add(line);
        }
        br.close(); // THIS IS IMPORTANT never forget to close a Reader :)
        return lines;
    }

    private static void writeLines(List<ParsedObject> objects) throws IOException {
        File file = new File("output.txt");
        BufferedWriter bw = new BufferedWriter(new FileWriter(file));
        for(ParsedObject object : objects) {
            // print the output line by line
            bw.write(object.originalLine);
        }
        bw.flush();
        bw.close();  // THIS IS IMPORTANT never forget to close a Writer :)
    }


    // our object that holds the information
    static class ParsedObject implements Comparable<ParsedObject> {

        // the original line, if needed
        public String originalLine;
        // the columns
        public Integer firstNumber;
        public String firstString;
        public Integer secondNumber;
        public Integer thirdNumber;
        public Integer fourthNumber;

        // parse line by line
        public static List<ParsedObject> from(List<String> lines) {
            List<ParsedObject> objects = new ArrayList<>();
            for(String line : lines) {
                objects.add(ParsedObject.from(line));
            }
            return objects;
        }

        // parse one line
        public static ParsedObject from(String line) {
            String[] splitLine = line.split("-");
            ParsedObject parsedObject = new ParsedObject();
            parsedObject.originalLine = line + "\n";
            parsedObject.firstNumber = Integer.valueOf(splitLine[0]);
            parsedObject.firstString = splitLine[1];
            parsedObject.secondNumber = Integer.valueOf(splitLine[2]);
            parsedObject.thirdNumber = Integer.valueOf(splitLine[3]);
            parsedObject.fourthNumber = Integer.valueOf(splitLine[4]);
            return parsedObject;
        }

        @Override
        public int compareTo(ParsedObject other) {
            return other.thirdNumber.compareTo(this.thirdNumber);
        }
    }
}

If you have any more question feel free to ask :) An here is an the example objects list after parsing and sorting.