我在格式化代码时遇到了一些麻烦，无法提供正确的输出。我是Java的初学者，所以我希望我犯了一些相当愚蠢的错误，但是这里有。
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：
输出文件看起来像这样：
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：
我需要将名称（第一个和最后一个）打印 with 最低和最高等级。
等级的降序显然是递增的，所以 需要修复。
我还需要在每个年级打印的名称（第一个和最后一个） 最后有组织的降序列表，现在名称与成绩不符。
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;
}
}
}
答案 0 :(得分：3)
问题是：
- 我需要打印等级的名称（第一个和最后一个） 最小和最大。
保留两个Strings，每个Arrays.sort()包含具有最低和最高等级的人的姓名，就像您使用实际的最小值和最大值一样。
- 等级的降序显然是递增的，所以 需要修复。
看起来你已经对数组进行了排序，使其按升序排列（如果允许的话，请顺便查看t=st[i].grade;
st[i].grade=st[i+1].grade;
st[i+1].grade=t;
），所以不要从前到后打印，为什么不要'你从阵列的末尾开始打印它？这应该按降序打印。
- 我还需要在每个年级打印的名称（第一个和最后一个） 最后组织了降序列表。
您的成绩与正确的人不匹配，因为您正在切换阵列中每个人的成绩，而不是在阵列中切换人员。
见这里：
[Bob(50)][Sam(75)]让我们假装你有两个人，Bob和Sam，分别为50和75.
这里他们在数组中：[Bob(75)][Sam(50)]
使用上面的代码交换它们，最终会得到：{{1}}
修复此问题的更改非常简单。我会留给你弄清楚的。
答案 1 :(得分：0)
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();
}
}