百分比计算一直返回0[重复]

Question

我试图实现的是一个测试的评分系统，但是如果有错误的答案，变量百分比等级总是返回0。

参考代码：

import java.util.ArrayList;

public class Result
{
    private Test test;
    private ArrayList<String> correctAnswers;

    public Result()
    {
        this.correctAnswers = new ArrayList<>();
    }
    
   public void addTest(Test test) {
       this.test = test;
   }

   public Test getTest() {
       if(this.test != null) {
           return this.test;
        }     
        return null;   
   }
   
   public void addcorrectAnswers(String correctAnswers) {
       this.correctAnswers.add(correctAnswers);
   }
   
   public ArrayList<String> getCorrectAnswers() {
       return this.correctAnswers;
   }
   
   public String getGrade() {
           
        int counter = 0;
        
        for(String gradingAnswers : this.correctAnswers) {
            for(String answersTest : this.test.getAnswers()) {
                if(answersTest == gradingAnswers) {
                    counter++;
                }
            }
        }
        
        if(this.test.getAnswers().size() > 0){
            double percentGrade = (counter / this.correctAnswers.size()) * 100; //ISSUE IS HERE 
            if(percentGrade > 55) {
                return "Your score is " + percentGrade + "% ." + " You PASSED!!";
            }else if(percentGrade <= 55){
                return "Your score is " + percentGrade + "% ." + " You FAILED!!"; 
            }else {
                return "Could not return score !";
            }
       }
        return "Could not return answers or calculate";
    }
}   

Answer 1

柜台和这个。正确答案。size（）都是整数，所以“/”是整数运算符。尝试

   double percentGrade = ((float)counter / this.correctAnswers.size()) * 100;

强制进行浮动分割。

如果需要控制精度，我建议使用BigDecimal类及其子类。divide（）方法。

        BigDecimal.valueOf(counter ).divide(BigDecimal.valueOf(size),4, RoundingMode.CEILING).multiply(BigDecimal.valueOf(100));

Answer 2

转换为浮点数将确保您使用浮点数除法而不是整数除法。对于涉及更高精度的除法，整数除法通常是错误的选择。

double percentGrade=（（浮动）计数器/this。正确答案。大小（））*100//问题在这里，如果（百分比分数）