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所以我正在编写的程序读取 3 个不同的文本文件。一个文本文件包含名称，另外两个包含标记。

现在我已经正确地完成了所有事情，但是我想添加一件事，但我没有运气做对。

所以现在输出文件如下所示：

  25987 Alan
  IR101: 35.6      IR102: 20.7      Aggregate: 28.2 

  Class:       Fail       Outcome: Repeat Year!

  -------------------------------------------------------
  25954 Betty
  IR101: 70.2      IR102: 63.4      Aggregate: 66.8 

  Class:       2.1       Outcome: Proceed to Stage 2!

  -------------------------------------------------------
  25654 Chris
  IR101: 58.6      IR102: 35.1      Aggregate: 46.9 

  Class:       Fail       Outcome: Resit IR102!

  -------------------------------------------------------
  Etc

因此，我的程序根据名称从带有名称的文本文件中打印出顺序。例如，其中一个包含所有名称的文本文件的顺序是：Alan /n Betty /n Chris

现在我不希望订单出现在文本文件中的名称中，我希望订单是降序聚合标记。所以顺序应该是：

 25954 Betty
 IR101: 70.2      IR102: 63.4      Aggregate: 66.8 

 Class:       2.1       Outcome: Proceed to Stage 2!

 -------------------------------------------------------

 25654 Chris
 IR101: 58.6      IR102: 35.1      Aggregate: 46.9 

 Class:       Fail       Outcome: Resit IR102!

 -------------------------------------------------------

 25987 Alan
 IR101: 35.6      IR102: 20.7      Aggregate: 28.2 

 Class:       Fail       Outcome: Repeat Year!

 -------------------------------------------------------

这么久以来，我尝试了许多不同的解决方案，但都失败了。

程序代码：

public class SORTING {
static class Student {
    String id;
    String name;
    List<Double> marks;

    public Student(String id, String name) {
        this.id = id;
        this.name = name;
        marks = new ArrayList<Double>();
    }


    public void addMark(Double d) {
        marks.add(d);
    }
    public void writeToPW(PrintWriter out) {
        out.println(id + " " + name);
        double d = 0;
        for (int i = 0; i < marks.size(); i++) {
            out.printf("IR10%d: %.1f      ", (i+1), marks.get(i));
            d += marks.get(i);
        }
            out.printf("Aggregate: %.1f ", + d / marks.size());
            out.println("\n");
            double aggregate = (d/marks.size());


            if ((marks.get(0)<40)&&(marks.get(1)>=40)){
            out.print("Class:       Fail" + "       Outcome: Resit IR101");
            }

            if ((marks.get(0)>=40)&&(marks.get(1)<40)){
            out.print("Class:       Fail" + "       Outcome: Resit IR102!");
            }

            if ((marks.get(0)<40)&&(marks.get(1)<40)){
            out.print("Class:       Fail" + "       Outcome: Repeat Year!");
            }

            if((marks.get(0)>40)&&(marks.get(1)>40)&&(aggregate>70)){
            out.print("Class:       1st" + "       Outcome: Proceed to Stage 2!");
            }

            if((marks.get(0)>40)&&(marks.get(1)>40)&&(aggregate>=60)&&(aggregate<=69.9)){
            out.print("Class:       2.1" + "       Outcome: Proceed to Stage 2!");
            }
            //2.2 Class degree code.
            if((marks.get(0)>40)&&(marks.get(1)>40)&&(aggregate>=50)&&(aggregate<=59.9)){
            out.print("Class:       2.2" + "       Outcome: Proceed to Stage 2!");
            }

            if((marks.get(0)>40)&&(marks.get(1)>40)&&(aggregate>=40)&&(aggregate<=49.9)){
            out.print("Class:       3rd" + "       Outcome: Proceed to Stage 2!");
            }
            out.println("\n");
            out.println("-------------------------------------------------------");
        }
    }
public static void main(String[] args) throws IOException {
    //declare reader and writer
    BufferedReader reader = null;
    PrintWriter writer = null;

    //hash maps to store the data
    HashMap<String, Student> students = new HashMap<String, Student>();

    // list to maintain the original order
    List<Student> orderedStudents = new ArrayList<Student>();


    //read the  first file and store the data
    reader = new BufferedReader(new InputStreamReader(new FileInputStream(new File("IRStudents.txt"))));
    String line;
    String[] arg;
    while ((line = reader.readLine()) != null) {
        if (!line.startsWith("-")) {
            arg = line.split(" ");
            Student student = new Student(arg[0], arg[1]);
            students.put(arg[0], student);
            orderedStudents.add(student);
        }
    }
    reader.close();

    //read the second file, merge the data and output the data to the out file
    reader = new BufferedReader(new InputStreamReader(new FileInputStream(new File("IR101.txt"))));
    while((line = reader.readLine()) != null){
        arg = line.split(" ");
        students.get(arg[0]).addMark(Double.parseDouble(arg[1]));
    }


    reader = new BufferedReader(new InputStreamReader(new FileInputStream(new File("IR102.txt"))));
    while((line = reader.readLine()) != null){
        arg = line.split(" ");
        students.get(arg[0]).addMark(Double.parseDouble(arg[1]));
    }

    // Now we can do writing.
    writer = new PrintWriter(new FileOutputStream(new File("RankedList.txt")));
    for (Student s: orderedStudents) {
        s.writeToPW(writer);
    }
    writer.close();
}

}

4

1 回答 1

1

好吧，您需要使用https://docs.oracle.com/javase/8/docs/api/java/util/Collections.html#sort-java.util.List-java.util.Comparator对列表进行排序-。你给它一个比较器，它是 Comparator 接口的实现，基本上取两个 Student 对象并返回它们应该如何排序，在你的情况下，通过比较聚合标记。就像是

Collections.sort(orderedStudents, new Comparator<Student>() {
  public int compare(Student s1,Student s2){
    return s2.getAggregate().compareTo(s1.getAggregate());
  }
  });

并在您的 Student 类上公开一个 getAggregate() 方法，该方法实际计算聚合，而不是在漂亮的打印代码中进行该计算。

于 2015-04-15T14:54:58.227 回答