我如何找到这个学生数组中所有学生的最高、最低和总平均数

Posted 2023-03-17

【中文标题】我如何找到这个学生数组中所有学生的最高、最低和总平均数

【英文标题】：How do I find the highest, lowest and total average of all the students in this Array of students

【发布时间】：2019-03-01 20:19:24

【问题描述】：

我有一个良好的开端，但在试图找到阵列的最低和最高等级时遇到了困难。我还必须找到整个阵列的平均等级。

他们告诉这个网站是获得帮助的最佳场所

所以...如果有人可以帮助我，我将不胜感激

这就是我目前所拥有的

import java.util.Scanner;

public class Grades

 public static void main(String[]args)

  Scanner keyboard = new Scanner(System.in);
  String studentName;
  double studentScore;
  double [][]studentTestScores;
  double Average ;
  char LetterGrade;
  double LowestScore;


  final int numStudents = 2;
  final int numGrades = 3;


  Grades2 class1 = new Grades2 (numStudents,numGrades );
  studentTestScores = class1.getTestScoresArray();

  for( int StudentIndex = 0; StudentIndex < numStudents; StudentIndex++)
  
     System.out.println("Enter name of student " + (StudentIndex + 1));
     studentName = keyboard.nextLine();
     class1.setStudentName( studentName );



     for( int studentScoreIndex = 0; studentScoreIndex < numGrades; studentScoreIndex++)
     
        System.out.println("Enter test grade " + (studentScoreIndex + 1) + " grade of " + studentName);
        studentScore = keyboard.nextDouble();

        while( studentScore < 0 || studentScore > 100)
           System.out.println("Please enter a valid 
score" + (studentScoreIndex + 1) + " for " + 
studentName);
           studentScore = keyboard.nextDouble();
     

        keyboard.nextLine();
        class1.setScore(StudentIndex, studentScoreIndex, studentScore );            
     
   


  for( int StudentIndex = 0; StudentIndex < n 
umStudents; StudentIndex++ )
     System.out.print( class1.getStudentName( 
StudentIndex ) + " Test scores are ");

     Average    = class1.AverageTestScore( 
studentTestScores[ StudentIndex ] ); 
     LetterGrade = class1.getLetterGrade( Average );
     LowestScore = class1.getLowestScore( 
studentTestScores[ StudentIndex ]  );


     for( int studentScoreIndex =  
0;studentScoreIndex < numGrades; 
studentScoreIndex++)
        if( studentScoreIndex != numGrades  -1)
           System.out.print( studentTestScores[ 
StudentIndex ][ studentScoreIndex ] + ", " );
         else  
           System.out.print( studentTestScores[ 
StudentIndex ][ studentScoreIndex ] + " " );
        
     

     System.out.println("with an average of " + 
 String.format(" %.2f", Average) + ", letter grade " 
+ LetterGrade );
     System.out.println("\nLowest grade is " + 
LowestScore);
     System.out.println();

  

这是程序的第 2 部分

import java.util.ArrayList;

public class Grades2


private ArrayList <String> studentNames = new 
ArrayList <String> ();
private char [] LetterGrades = 'A', 'B', 'C' , 'D' 
, 
'F' ;
  private double [] [] studentTestScores;


public String getStudentName(int studentIndex)
  return studentNames.get(studentIndex);




public double AverageTestScore( double [] 
studentTestScores)
  double studentTestScoresTotal = 0;
  double studentTestScoresAverage;

  for( int studentTestScore = 0; studentTestScore < 
studentTestScores.length; studentTestScore++)
     studentTestScoresTotal = studentTestScoresTotal 
+ studentTestScores[ studentTestScore];
  
  studentTestScoresAverage = studentTestScoresTotal 
/ studentTestScores.length;
  return studentTestScoresAverage;



public double getLowestScore()
  double LowestScore = studentTestScores[0] ;

  for( int studentTestScore = 0; studentTestScore < 
studentTestScores.length; studentTestScore++)
     if ( studentTestScores[scoreIndex] < 
LowestScore)
     LowestScore = studentTestScores[scoreIndex];



  return LowestScore;




public char getLetterGrade( double TestScoreAverage 
    )

  char  LetterGrade = 'Z';

  if(TestScoreAverage < 60 )
     LetterGrade = 'F';
   else if ( TestScoreAverage < 70)
     LetterGrade = 'D';
   else if ( TestScoreAverage < 80)
     LetterGrade = 'C';
   else if ( TestScoreAverage < 90)
     LetterGrade = 'B';
   else if ( TestScoreAverage < 100)
     LetterGrade = 'A';
  

  return LetterGrade;



public void setStudentName(String studentName)
  studentNames.add(studentName);



public void setScore(int studentIndex, int 
scoreIndex, double Score)
  studentTestScores[ studentIndex ][ scoreIndex ] = 
Score;



public double [][] getTestScoresArray()
  return studentTestScores;
      

public Grades2( int numStudents, int numGrades)
  studentTestScores = new double [ numStudents ][ 
numGrades ];

【问题讨论】：

那么您遇到的具体问题是什么？

Java 中的变量和方法应该是小写的。至少，我建议调整您的方法 AverageTestScore 以与其他小写方法保持一致。

您使用的是哪个 Java 版本？ Chota Bheem 的答案适用于 Java 8 或更高版本。下面你想看看this answer，特别是第二个代码块。

【参考方案1】：

您可以使用以下方法简单地找到平均值、最小值和最大值：

public double AverageTestScore(double[] studentTestScores) 
    return Arrays.stream(studentTestScores).average().orElse(0);


public double getLowestScore(double[] scores) 
    return Arrays.stream(scores).min().orElse(0);


public double getHighestScore(double[] scores) 
    return Arrays.stream(scores).max().orElse(0);

【参考方案2】：

在 main 方法的第二个 for 循环中，您可以使用以下代码获取每个学生 (studentTestScores[StudentIndex])。它为您提供了您要求的“最高、最低和总平均”值：

DoubleSummaryStatistics statistics = Arrays.stream(studentTestScores[StudentIndex])
        .boxed()
        .collect(Collectors.summarizingDouble(Double::doubleValue));
double lowestScore = statistics.getMin();
double averageScore = statistics.getAverage();

查看DoubleSummaryStatistics 的JavaDoc。也许您也想使用其他一些方法。

这应该让您不必编写/测试代码来自己计算值。