Now its time to design a class for out program. Let name the class, TestGrade.java

Before we go into the coding part, we can write the structure and required elements in english.

we need :

score  :  A private int type field to hold the score that is numeric.
Constructor  : Accepts an argument for the score and store it in score variable.
setScore : Mutator method that accepts an argument for the score field.
getScore  : Accessor method that returns the value of the score field.
getLetterGrade  : A method that uses the nested decision structure above to determine a letter grade for the score.

The above structure of a class can be explained more formally using a diagram, which is called UML diagram.

Now, we will write the actual code following the above diagram.

/**
* The TestGrade class will determine a letter grade
*  based on a numeric testscore
*
*/
//This is how we write the class

public class TestGrade
{
           private   int   score;

         /**
           * The constructor accepts an argument
           * for the score field
           */

          public TestGrade(int s )
          {
                score =  s ;
          }

          /**
            * The setScore method accepts an argument
            * for the score field
            */

            public void SetScore(int s)
            {
              score = s;
            }

           /**
            * The getScore  method returns the score field.
            *
            */
           public int getScore()
           {
            return score;
           }

             /**
            * The getLetterGrade returns the letter
            * grade for the test score.
            */
 
             public char getLetterGrade()
             {
                    char grade;

                    if (score < 60)
                     {
                          grade =  'F';
                     }
                          else
                            {
                                   if(score < 70)
                                       {
                                          grade = 'D' ;
                                       }
                                       else
                                           {
                                                    if (score < 80)
                                                        {
                                                        grade = 'C' ;
                                                        }
                                                       else
                                                             {
                                                               if (score < 90)
                                                                     {
                                                                        grade = 'B';
                                                                     }
                                                                  else 
                                                                       {
                                                                       grade = 'A';
                                                                      }     
                                                      }
                                               }
               return grade ;
                        }
             }  
}

The above code is a very basic approach to code our class, but there are better ways to implement this code. I am going to stay with this anyway and will move to the driver class or the class which contains the main method.

        import java.util.Scanner

            /**
             *  This program uses the TestGrade class to determine
             * a letter grade for a numeric test grade
             */

    public class TestResults
        {
                public static void main(String[]  args)
                    {
                       int testScore ;                       //To hold a test score
                       char letterGrade;              //To hold a letter grade

                     //Create a Scanner object to read input
                      Scanner keyboard = new Scanner(System.in);

                      //Get the numeric test score
                      System.out.print("ENter your numeric test score and" + "I will show you the grade");
                   
                       testScore = keyboard.nextInt();

                      //Create a TestGrade object with the numeric score
                     TestGrade test =  new TestGrade(testScore);
                    
                     //Now get the letter grade.
                     letterGrade  = test.getLetterGrade();


                      //Display the grade.
                      System.out.print("Your grade is " +test.getLetterGrade());

                    }

        }