PreLab 6: More Classes

1. Find the base 10 value of each of the following 12-bit two's complement integers (show work), find the sum in 12-bit two's complement (as the computer would do it), and convert that 12-bit two's complement answer to base 10 (show work).

            Two's complement                Base 10 Equivalent
   
          1 1 1 1 0 0 1 1 1 1 0 0    ___________________________________
   
       +  1 1 1 1 1 1 1 0 1 0 0 0    ___________________________________
       --------------------------
   
   Sum  _________________________    ___________________________________
   
   
   
   
   
   
   
   

2. Did overflow occur in the sum above? Give reasons for your answer.

    

    

3. Constructors are a special type of method included in a class definition.
   1. When is a constructor executed?

       

       

   2. What are the rules for
      • the name of a constructor?

         

      • the return type?

         

4. Suppose a teacher wants a program to keep track of grades for students and decides to create a student class for her program as follows:
   • Each student will be described by three pieces of data: his/her name, his/her score on test #1, and his/her score on test #2. (The test grades will be type int.)
   • There will be one constructor which will have one argument -- the name of the student.
   • There will be four methods: an accessor method getName, which will return the student's name; inputGrades, which will prompt for and read in the student's test grades; getAverage, which will compute and return the student's average, and highestScore, which will return the highest of the two test grades.
   The following is an incomplete class declaration. Fill in the data declarations and methods as indicated in the comments.

   //*****************************************************
   // Student.java
   //
   // A class representing a student; holds info about 
   // the student's name and test grades.
   //*****************************************************
   public class Student
   {
     //declare instance data
   
     ____________________________________________  // name
                                  
     ____________________________________________  // grade for test #1
   
     ____________________________________________  // grade for test #2
   
   
     //---------------------------------------------------
     // Constructor -- creates a student object whose name 
     // is the value passed in.
     //---------------------------------------------------
     public Student(String studentName)
     {
         // Assign the instance variable name the value passed in
         // and initialize the two test grades to 0
   
   
   
   
   
   
     }
   
   
     //---------------------------------------------------
     // inputGrades: Prompts for and reads in grades for 
     // the student's two tests.  No parameters or return value.
     //---------------------------------------------------
     public void inputGrades()
     {
       ... body of inputGrades ...(don't fill in)
     }
   
     //---------------------------------------------------
     // getName: returns the student's name. 
     //---------------------------------------------------
   
     _________________________________________________  //fill in header
     {
         // fill in the body of the method (just one line!)
   
         _____________________________________________________;
     }
   
   
     //---------------------------------------------------
     // getAverage: Computes and return the average of the 
     // student's test grades.  No parameters.
     //---------------------------------------------------
   
     _____________________________________________________  //fill in header
     {
   
        // Compute and return the average (it can be done in one statement)
   
   
        _______________________________________________________ ;
     }
   
   
     //------------------------------------------------------
     // highestScore:  Returns the highest test grade - no
     // parameters.
     // -----------------------------------------------------
     
     ______________________________________________________  // fill in header
     {
        int highGrade;   // a local variable to hold the highest grade
   
        // Write an if statement to assign highGrade the highest of the
        // two test grades
   
   
   
   
   
   
   
        // Return the highest grade
        return highGrade;
      }
   }
   

5. The following is part of a class that uses the Student class. Fill in the two if statements requested in the commments.

   public class StudentGrades
   {
      public static void main (String[] args)
      {
         Student student1 = new Student ("Sarah");
         Student student2 = new Student ("John");
   
         student1.inputGrades();
         student2.inputGrades();
   
         double average1 = student1.getAverage();
         
         // Write an if ...else... statement that prints the message
         // "Great work!" if Sarah's average is greater than 84; "Doing
         // fine" if the average is between 70 and 84 (inclusive);
         // "Work harder" otherwise
   
   
   
   
   
   
   
   
         // Write an if ... else that determines who has the highest
         // average - use the getName method to print the name of the person
   
   
   
   
   
   
   
   
         }
   }