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我在格式化我的代码以提供正确的输出时遇到了一些麻烦。我是 Java 的初学者，所以我希望我犯了一些相当愚蠢的错误，但这里是这样。

我输入的文本文件是：

John Smith  90
Barack Obama    95
Al Clark    80
Sue Taylor  55
Ann Miller  75
George Bush 58
John Miller 65

输出文件看起来有点像这样：

John Smith  90
Barack Obama    95
Al Clark    80
Sue Taylor  55
Ann Miller  75
George Bush 58
John Miller 65

Students with excellent grades:
John Smith  90
Barack Obama    95

Students with ok grades:
Al Clark    80
Ann Miller  75
John Miller 65

Students with failure grades:
Sue Taylor    55
George Bush  58


Lowest Grade: Sue Taylor 55 
Highest Grade: Barack Obama 95
Average of Grades: 74


Grades in descending order: 
John Smith 55 
Barack Obama    58 
Al Clark    65 
Sue Taylor  75 
Ann Miller  80 
George Bush 90 
John Miller 95

我正在寻找的输出是这样的：

输出文件看起来有点像这样：

John Smith  90
Barack Obama 95
Al Clark 80
Sue Taylor   55
Ann Miller   75
George Bush  58
John Miller  65


Students with excellent grades:
John Smith  90
Barack Obama 95


Students with ok grades:
Al Clark   80
Ann Miller   75
John Miller  65


Students with failure grades:
Sue Taylor    55
George Bush  58


Lowest Grade: Sue Taylor 55
Highest Grade: Barack Obama 95
Average of Grades: 74


Grades in descending order: 
Barack Obama 95
John Smith 90
Al Clark 80
Ann Miller 75
John Miller 65
George Bush 58
Sue Taylor 55

问题是：

  1. 我需要打印姓名（名字和姓氏）以及最低和最高等级。

  2. 成绩的降序显然是升序，所以需要固定。

  3. 我还需要在最后有组织的降序列表中打印每个等级的名称（第一个和最后一个），现在这些名称与等级不匹配。

这是我的代码：

import java.util.Scanner;
import java.io.*;

public class Students
{
public static void main (String[] args) throws IOException
{   
    String first_name, last_name;
    int grade, total=0, count=0;
    int min, max;

    double average;

     int excellentTotal = 0;
     int okTotal = 0;
     int failureTotal = 0;

    Scanner fileInput = new Scanner(new File("students.txt"));
    Student st[] = new Student [100];
    while (fileInput.hasNext())
    {
        first_name = fileInput.next();
        last_name = fileInput.next();
        grade = fileInput.nextInt();    
        st[count] = new Student(first_name, last_name, grade);
        count++;
        total = total + grade; 
    }

    for (int i=0; i<count;i++)
    {
        System.out.println(st[i]);
    }

    System.out.println("\nStudents with excellent grades:");
    for (int i=0; i<count;i++)
    {
        if (st[i].grade > 89)
        {
            System.out.println(st[i]);
            excellentTotal += st[i].grade;
        }
    }

    System.out.println("\nStudents with ok grades:");
    for (int i=0; i<count;i++)
    {
        if (st[i].grade >=60 && st[i].grade <=89)
        {
            System.out.println(st[i]);
            okTotal += st[i].grade;
        }
    }

    System.out.println("\nStudents with failure grades:");
    for (int i=0; i<count;i++)
    {
        if (st[i].grade < 60)
        {
            System.out.println(st[i]);
            failureTotal += st[i].grade;
        }
    }       


    min = st[0].getGrade();
    max = st[0].getGrade();
    for (int i = 0; i < count; i++) 
    {
        if (max.grade < st[i].grade)
        {
            max = st[i];
        }
        if (min.st[i] > st[i].grade)
        {
            min = st[i].grade;
        }
        total = excellentTotal + okTotal + failureTotal;
    }

    System.out.println();
    System.out.println("Lowest Grade: " + min);
    System.out.println("Highest Grade: " + max);
    System.out.println("Average of Grades: " + total/count);

    int t, swap = 0;
    do 
    { 
        swap = 0; 
        for (int i=0; i<count-1; i++) 
        {
            if (st[i].getGrade()>st[i+1].getGrade()) 
            {
                t=st[i].grade; 
                st[i].grade=st[i+1].grade; 
                st[i+1].grade=t; 
                swap++;
            }
        } 
    }
    while (swap>0);

    System.out.println("\nGrades in descending order: ");

    for (int i=0; i<count;i++)
    {
         System.out.print (st[i] + " ");
         System.out.println ();
    }
}
static class Student
{
    private String fname, lname;
    private int grade;

    public Student(String fname, String lname, int grade)
    {
        this.fname = fname;
        this.lname = lname;
        this.grade = grade;
    }

    public int getGrade() 
    {
        return grade;
    }

    public void setGrade(int grade) 
    {
        this.grade = grade;
    }


    public String toString()
    {
        return fname + " " + lname + "\t" + grade;
    }


}
}
4

2 回答 2

3

问题是：

  1. 我需要打印姓名（名字和姓氏）以及最低和最高等级。

保留两个Strings，每个都包含具有最低和最高等级的人的姓名，就像你对实际的最小值和最大值所做的那样。

  1. 成绩的降序显然是升序，所以需要固定。

看起来您已经对数组进行了排序，使其按升序排列（顺便说一句，Arrays.sort()如果允许的话，请查看），所以不要从前到后打印它，为什么不从最后开始打印它你的阵列？这应该按降序打印。

  1. 我还需要在最后有组织的降序列表中打印每个等级的名称（第一个和最后一个）。

您的成绩与正确的人不匹配，因为您正在切换数组中每个人的成绩，而不是切换数组中的人。

看这里：

t=st[i].grade; 
st[i].grade=st[i+1].grade; 
st[i+1].grade=t;

假设您有两个人 Bob 和 Sam，他们的成绩分别为 50 和 75。

它们在数组中：[Bob(50)][Sam(75)]

使用上面的代码交换它们，你最终会得到：[Bob(75)][Sam(50)]

解决此问题的更改是微不足道的。我会留给你弄清楚。

于 2012-12-24T15:50:16.177 回答
0

好吧，我会做一个快速而肮脏的例子：

import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;

public class Students {

List<Student> students = new ArrayList<Student>();

public Students() {
    // create quick list, no reading from file, don't use arrays if you can help it
    students.add(new Student("a", 1));
    students.add(new Student("b", 2));
    students.add(new Student("c", 3));

    // sort list descending
    Collections.sort(students, new Comparator<Student>() {
        @Override
        public int compare(Student student1, Student student2) {
            return -1 * student1.grade.compareTo(student2.grade);
        }
    });
}

public void showDescending() {
    // just so the list that was sorted descending
    System.out.println(students);
}

public void showForRange(Integer minGrade, Integer maxGrade) {
    // show all students with grades between minGrade and maxGrade
    for (Student s : students) {
        if (s.grade >= minGrade && s.grade <= maxGrade) {
            System.out.println(s);
        }
    }
}

public class Student {
    String name;
    Integer grade;

    public Student(String name, Integer grade) {
        this.name = name;
        this.grade = grade;
    }

    // use toString to easily show name with grade for each student in list
    @Override
    public String toString() {
        return name + " " + grade;
    }

}

public static void main(String[] args) {
    Students s = new Students();
    s.showForRange(100, 90);
    s.showForRange(89, 80);
    s.showDescending();

}


}
于 2012-12-24T16:09:43.213 回答