java - 如何找到两个人的最佳答案

Question

我正在尝试找到从控制台输入的两个最大数字。我找到了第一个，但第二个的解决方案不起作用。程序正在编译并运行。这是代码。

import java.util.Scanner;

public class FindingSecondHighestScore_4_09 {

    public static void main(String[] args)
    {
        Scanner input = new Scanner(System.in);

        double max = 1;
        double score2 = 0;
        String firstName = "";
        String secondName = null;
        System.out.println("Enter number of students: ");
        int x = input.nextInt();
        while(x > 0)
        {
            System.out.println("Enter Sudent's name");
            String name = input.next();
            System.out.println("Enter Student's score");
            double score = input.nextDouble();

            //find max
            if(score > max)
            {
                max = score;
                firstName = name;
            }

            //find second max
            if(max < score2  || score < score2)
            {
                max = score2;
                score = score2;
            }
            else if(max > score2  && score2 < score)
            {
                score2 = score;
                secondName = name;
            }


            x--;
        }
        System.out.println("The student: " + firstName + " has the greatest score: " + max);
        System.out.println("Second studemt " + secondName + " with second results: " + score2);

    }

}

Answer 1

这是一个更复杂的实现(我今天的起床练习):

import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;

public class TopScores {

    private static final int TOP_SELECTION_SIZE = 2;

    public static class Student {
        private final String name;
        private double score;

        public Student(String name) {
            if (name == null || name.length() == 0) {
                throw new IllegalArgumentException("Name cannot be empty");
            }
            this.name = name;
        }

        public String getName() {
            return name;
        }

        public double getScore() {
            return score;
        }

        public void setScore(String score) {
            try {
                this.score = Double.parseDouble(score);
            } catch (NumberFormatException e) {
                throw new IllegalArgumentException("Illegal score: " + score);
            }
        }

        @Override
        public String toString() {
            return String.format("%s with score %s", name, score);
        }
    }

    public static void main(String[] args) {

        List<Student> students = new ArrayList<TopScores.Student>();
        System.out.println("Please enter students. Press <RETURN> to stop.");
        Scanner input = new Scanner(System.in);
        boolean enteringData = true;
        while (enteringData) {
            try {
                System.out.print("Enter student's name: ");
                Student student = new Student(input.nextLine());
                System.out.print("Enter student's score: ");
                student.setScore(input.nextLine());
                for (int i = 0; i < students.size(); i++) {
                    if (student.getScore() > students.get(i).getScore()) {
                        students.add(i, student);
                        break;
                    }
                }
                if (students.size() == 0) {
                    students.add(student);
                }
            } catch (IllegalArgumentException e) {
                enteringData = false;
            }
        }

        int studentsToDisplay = Math.min(TOP_SELECTION_SIZE, students.size());
        if (studentsToDisplay > 0) {
            System.out.println("Top students:");
            for (int i = 0; i < studentsToDisplay; i++) {
                System.out.println("* " + students.get(i));
            }
        } else {
            System.out.println("No students to display");
        }
    }
}

我创建了一个单独的学生类，它保存姓名和分数，验证输入并为一名学生创建显示格式。

为了确定最高分，我通过将每个新学生添加到正确的位置，将所有输入的学生排序在列表中。

用户不必事先输入学生人数，但可以通过输入空行(或无效分数)来终止数据输入。

数据输入完成后，将打印所需的得分最高的学生人数。

这种方式更加灵活；打印前 3 名或前 10 名学生只需更改 TOP_SELECTION_SIZE 的值即可。

最重要的收获:尽可能在类里面(在本例中为学生)思考，并将合理的责任委派给每个类(class)。