More Java Fun

[JollyMisanthropeParticipant 3356]

This time I just have a small section of code that is confusing me. Everything else works fine. Basically I’m creating a Java class that deals with taking in quiz and test scores and outputting the individual grades for each, the final grade (as a percentage), and a letter grade A,B,C,D,F. If I comment out this code in particular and run the rest it does everything perfectly. But for some reason it gives me an error that says it isn’t returning a “char” value, which would be the letter grade. Does it need a final else statement at the end?

  public char getLetterGrade()
  {
  double percentGrade = this.getPercentGrade();
  
  if(percentGrade >= 0 && percentGrade <60)
  {
  return 'F';
  }
  else
  {
  if(percentGrade >= 60.0 && percentGrade <70.0)
  {
  return 'D';  
  }
  else
  {
  if(percentGrade >= 70.0 && percentGrade <80.0)
  {
  return 'C';
  }
  else
  {
  if(percentGrade >= 80.0 && percentGrade <90.0)
  {
  return 'B';
  }
  else
  {
  if(percentGrade >= 90.0 && percentGrade <=100.0)
  {
  return 'A';
    }
  
  }
   }
    }
     }  
      }

The Children of Doom... Doom's Children. They told my lord the way to the Mountain of Power. They told him to throw down his sword and return to the Earth... Ha! Time enough for the Earth in the grave.

[AttonParticipant]

I haven’t mess around with Java a lot but try default return of Z.

A MGTOW is a man who is not a woman's bitch!

[JollyMisanthropeParticipant 3356]

That did the trick. Just needed to add one more else with just a return. Cheers!

The Children of Doom... Doom's Children. They told my lord the way to the Mountain of Power. They told him to throw down his sword and return to the Earth... Ha! Time enough for the Earth in the grave.

[13-JzzalParticipant 134]

You could also do it like this:

public char getLetterGrade()
{
  double percentGrade = this.getPercentGrade();
  
  if(percentGrade <60)
  {
  return 'F';
  }
  else if (percentGrade >= 60 && percentGrade <70.0)
  {
  return 'D';  
  }
  else if(percentGrade >= 70.0 && percentGrade <80.0)
  {
  return 'C';
  }
  else if(percentGrade >= 80.0 && percentGrade <90.0)
  {
  return 'B';
  }
  else//This will return an A if the student has more than 90%.
  {
 return 'A';
  }
} 

[JollyMisanthropeParticipant 3356]

OK one more question. Now I need to confirm if the grade information I entered matches another instance of grade with either similar or different numbers.

public class TestGrade
{
  public static void main(String[] args)
  {
     Grade grade1 = new Grade();

    
     grade1.setQuiz1(10);
     grade1.setQuiz2(10);
     grade1.setQuiz3(10);
     grade1.setmidTerm(100);
     grade1.setfinalGrade(100);
     
    
     System.out.println("The percent grade is: " +    grade1.getPercentGrade() + "\n" +
                         "The letter Grade is: " +    grade1.getLetterGrade());

            
     System.out.println(grade1);
    
     Grade grade2 = new Grade(10,10,10,100,100);

     System.out.println(grade1.equals(grade2)); // prints true

  }
}

___________________________________

 public boolean equals(Object obj)
  {
  if(!(obj instanceof Grade))
  {
 return false; 
  }
  Grade other = (Grade)obj;
  
  return this.getPercentGrade() == other.getPercentGrade();
  }

As of now I always get false as a printout.

The Children of Doom... Doom's Children. They told my lord the way to the Mountain of Power. They told him to throw down his sword and return to the Earth... Ha! Time enough for the Earth in the grave.

[13-JzzalParticipant 134]

I am not sure why your code always returns false.

 public boolean equals(Object obj)
  {
  if(!(obj instanceof Grade))
  {
 return false; 
  }
  Grade other = (Grade)obj;
  
  return this.getPercentGrade() == other.getPercentGrade();
  }

seems to work fine for me.
If you try this:
return this.getPercentGrade().equals(other.getPercentGrade());
what happens?

My guess is that your getPercentGrade() method does not simply return and Integer like this?

public int getPercentGrade() {
return finalGrade;
}

[JollyMisanthropeParticipant 3356]

Here’s the method for getPercentGrade

 public double getPercentGrade()
  {
  double quizWeight = (quiz1 + quiz2 + quiz3)*25.0/30.0;
  double midWeight = (midTerm) * (35.0/100.0);
  double finalWeight = (finalGrade) * (40.0/100.0);
  Math.round(quizWeight);
  Math.round(midWeight);
  Math.round(finalWeight);
  return quizWeight + midWeight + finalWeight;
  }

The Children of Doom... Doom's Children. They told my lord the way to the Mountain of Power. They told him to throw down his sword and return to the Earth... Ha! Time enough for the Earth in the grave.

[JollyMisanthropeParticipant 3356]

Says: Cannot invoke equals (double) on the primitive type double.

The Children of Doom... Doom's Children. They told my lord the way to the Mountain of Power. They told him to throw down his sword and return to the Earth... Ha! Time enough for the Earth in the grave.

[13-JzzalParticipant 134]

JollyMisanthrope wrote:

Says: Cannot invoke equals (double) on the primitive type double.

Ok that was to be expected.

If i try your code it works fine for me.

public static void main(String[] args) {
// TODO Auto-generated method stub
Grade grade1 = new Grade();
grade1.setQuiz1(10);
grade1.setQuiz2(10);
grade1.setQuiz3(10);
grade1.setMidTerm(100);
grade1.setFinalGrade(100);
Grade grade2 = new Grade(10,10,10,100,100);
System.out.println(grade1.getPercentGrade());
System.out.println(grade2.getPercentGrade());
System.out.println(grade1.equals(grade2));
}

returns:

100.0
100.0
true

Could it be the case, that java does not use your custom “equals” method but the standard “equals” method? In that case it would return false.
I do not know why it would do that, though. As long as “equals” is defined inside the “Grade” class it should be using that one.

[JollyMisanthropeParticipant 3356]

For some reason the grade percentage isn’t rounding to two decimal places. Any advice? Is Math.round the wrong method to use?

public class Grade extends Object
{
  private double quiz1;
  private double quiz2;
  private double quiz3;
  private double midTerm;
  private double finalGrade;
  
  public Grade ()
  {
this(0,0,0,0,0); 
  }
  
  public Grade (double quiz1, double quiz2, double quiz3,
                double midTerm, double finalGrade)
  {
  
  }
  public void setQuiz1(double quiz1)
  {
  if(quiz1>10)
  {
  this.quiz1 = 10;
  }
  else
  {
  if(quiz1<0)
  {
  this.quiz1 =0;
  }
  else
  {
  this.quiz1 = quiz1;
  }
  }
  }
  public double getQuiz1()
  {
  return this.quiz1;
  }
  
   public void setQuiz2(double quiz2)
  {
  if(quiz2>10)
  {
  this.quiz2 = 10;
  }
  else
  {
  if(quiz2<0)
  {
  this.quiz2 =0;
  }
  else
  {
  this.quiz2 = quiz2;
  }
  }
  }
  public double getQuiz2()
  {
  return this.quiz2;
  }
  
   public void setQuiz3(double quiz3)
  {
  if(quiz3>10)
  {
  this.quiz3 = 10;
  }
  else
  {
  if(quiz3<0)
  {
  this.quiz3 =0;
  }
  else
  {
  this.quiz3 = quiz3;
  }
  }
  }
  public double getQuiz3()
  {
  return this.quiz3;
  }

   public void setmidTerm(double midTerm)
  {
  if(midTerm>100)
  {
  this.midTerm = 100;
  }
  else
  {
  if(midTerm<0)
  {
  this.midTerm =0;
  }
  else
  {
  this.midTerm = midTerm;
  }
  }
  }
  public double getmidTerm()
  {
  return this.midTerm;
  }
  
   public void setfinalGrade(double finalGrade)
  {
  if(finalGrade>100)
  {
  this.finalGrade = 100;
  }
  else
  {
  if(finalGrade<0)
  {
  this.finalGrade = 0;
  }
  else
  {
  this.finalGrade = finalGrade;
  }
  }
  }
  public double getfinalGrade()
  {
  return this.finalGrade;
  }
  
  public double getPercentGrade()
  {
  
  double quizWeight = (quiz1 + quiz2 + quiz3)*25.0/30.0;
  double midWeight = (midTerm) * (35.0/100.0);
  double finalWeight = (finalGrade) * (40.0/100.0);
  Math.round(quizWeight);
  Math.round(midWeight);
  Math.round(finalWeight);
  return quizWeight + midWeight + finalWeight;
  }
  public char getLetterGrade()
  {
  double percentGrade = this.getPercentGrade();
  
  if(percentGrade >= 0 && percentGrade <60)
  {
  return 'F';
  }
  else
  {
  if(percentGrade >= 60.0 && percentGrade <70.0)
  {
  return 'D';  
  }
  else
  {
  if(percentGrade >= 70.0 && percentGrade <80.0)
  {
  return 'C';
  }
  else
  {
  if(percentGrade >= 80.0 && percentGrade <90.0)
  {
  return 'B';
  }
  else
  {
  if(percentGrade >= 90.0 && percentGrade <=100.0)
  {
  return 'A';
    }
  else{
  
  return 'Z';
  }
  }
   }
    }
     }  
      }
  public boolean equals(Object obj)
  {
  if(!(obj instanceof Grade))
  {
 return false; 
  }
  Grade other = (Grade)obj;
  
  return this.getPercentGrade() == other.getPercentGrade();
  }
  
  public String toString()
  {
  
  return "Quiz1: "    + this.getQuiz1() +"\n" +
         "Quiz2: "    + this.getQuiz2() +"\n" +
 "Quiz3: "    + this.getQuiz3() +"\n" +
         "Mid Term: " + this.getmidTerm() + "\n" +
 "Final: "    + this.getfinalGrade() + "\n";
  }
}

public class TestGrade
{
  public static void main(String[] args)
  {
     Grade grade1 = new Grade();

    
     grade1.setQuiz1(8);
     grade1.setQuiz2(10);
     grade1.setQuiz3(5);
     
     grade1.setmidTerm(87);
     grade1.setfinalGrade(91);
     
     
     
     System.out.println("The percent grade is: " +    grade1.getPercentGrade() + "\n" +
                         "The letter Grade is: " +    grade1.getLetterGrade());

            
     System.out.println(grade1);
    
     Grade grade2 = new Grade(10,10,10,100,100);

     System.out.println(grade1.equals(grade2)); // prints true

  }
}

The Children of Doom... Doom's Children. They told my lord the way to the Mountain of Power. They told him to throw down his sword and return to the Earth... Ha! Time enough for the Earth in the grave.

[13-JzzalParticipant 134]

Math.round(double a) will add 0.5 and then give that value to the Math.floor() Method which will round down.

So: 1.6 + 0.5 = 2.1 which will be rounded to two.

To get decimals you will have to muliply your original number and divide the result of Math.round(double a);
Like this:

public static void main(String[] args) {
double rand = Math.random()*1000;
System.out.println(rand);
System.out.println(Math.round(rand));
double round = Math.round(rand*100);
round = round/100;
System.out.println(round);
}

Output:

498.5190839276097
499
498.52

However, round = Math.round(rand*100)/100; will not work. I am not quite sure why but the division has to be seperate.

Alternatively you can use the Math.rint(double a).
Using this you can do it like this:
round = Math.rint(rand*100)/100;
rint() rounds differently though. 1.5 will be rounded up while 2.5 will be rounded down.

For other numbers such as 2.7 or 1.2 both Methods will return the same result.

[JollyMisanthropeParticipant 3356]

I appreciate it my good sir!

The Children of Doom... Doom's Children. They told my lord the way to the Mountain of Power. They told him to throw down his sword and return to the Earth... Ha! Time enough for the Earth in the grave.

[Author]

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