created July 15, 2006; edits Nov 11, 2012

Programming Exercises

1.   Examine the following Employee class.

class Employee implements Comparable<Employee>
  private String firstName;
  private String lastName;
  private int birthYear;

  String getFirstName()  { return firstName; }
  String getLastName()   { return lastName; }
  int    getBirthYear()  { return birthYear; }
  public Employee( String f, String l, int year )
    firstName = f; lastName = l; birthYear = year;
  public String toString(){ finish this }
  public int compareTo( Employee other ) { finish this }

Finish the compareTo() method using all three of the instance variables. Access them using the getX() methods. Compare two employees by first looking at their last names. If the names are different, return the value the String method compareTo() returns with the last names. If the names are equal, look at the first name and return the value the String method compareTo() returns. If both parts of the name are equal, return the difference of the birthYears so that the older employee precedes the younger employee.

Test your implementation using this class:

import java.util.Arrays;

class EmployeeTester
  public static void main ( String[] args )
    Employee[] workers = new Employee[12];
    workers[0] = new Employee( "Fred", "Adams",  1963);
    workers[1] = new Employee( "John", "Adams",  1959);
    workers[2] = new Employee( "Elmer", "Adams",  1976);
    workers[3] = new Employee( "Nancy", "Devon",  1963);
    workers[4] = new Employee( "Andrew", "Lewis",  1983);
    workers[5] = new Employee( "Douglas", "Page",  1981);
    workers[6] = new Employee( "Donald", "Wolder",  1963);
    workers[7] = new Employee( "Henry", "Wolder",  1972);
    workers[8] = new Employee( "Robert", "Wolder",  1959);
    workers[9] = new Employee( "Howard", "Cohen",  1933);
    workers[10] = new Employee( "Howard", "Cohen",  1958);
    workers[11] = new Employee( "Donald", "Rice",  1935);
    Arrays.sort( workers );
    for ( int j=0; j<workers.length; j++ )
      System.out.println( workers[j].toString() );


2.   Examine the following Diamond class.

class Diamond implements Comparable<Diamond>
  private String stockNumber;
  private int carot;       /* size of the diamond */
  private String clarity;  /* clarity grade of the diamond */
  private char color;      /* color grade D-Z */
  private String cut;      /* name of the cut */

  String getStock()   { return stockNumber; }
  double getCarot()   { return carot; }
  String getClarity() { return clarity; }
  char   getColor()   { return color; }
  String getCut()     { return cut; }
  public Diamond( String s, double car, String clar, char col, String ct )
    stockNumber = s;  carot = car; clarity = clar; color = col; cut = ct;  
  public String toString(){ finish this }
  public int compareTo( Diamond other ) { finish this }

The size of a diamond is measured in carets, usually less than 5.0. The clarity grade of a diamond is give as a two or three letter code, FL, IF, VVS1, VVS2, VS1, VS2, SI1, SI2, I1, I2, I3. FL (flawless) is the best, I3 is the worst. The color grade is a one letter code, D through Z. D is the best, Z is the worst. The cut is the name of the pattern the diamond has been cut into.

Finish the toString() and the compareTo() methods. Write compareTo() so that diamonds are ordered first by caret, then by clarity OR color, whichever is better for the particular diamond. Since there are 23 grades of color, but only 11 grades of clarity, regard the first two color grades as equal in grade to the first grade of clarity, the next two color grades equal in grade to the second grade of clarity, and so on. Write compareTo() so that better diamonds are to the left of poor diamonds. This means that

goodDiamond.compareTo( poorDiamond )

returns a negative value. Notice that large caret diamonds will appear first on the list, the reverse of the usual order for numbers.

In comparing the codes for clarity, you will need a series of if statements. It might be useful to write a separate compareClarity() method as part of the class. Use this testing class:

import java.util.Arrays;

class DiamondTester
  public static void main ( String[] args )
    Diamond[] stones = new Diamond[16];
    stones[0] = new Diamond( "A1023", 1.0, "VS1",  'F', "brilliant");
    stones[1] = new Diamond( "A5911", 1.1, "VVS2", 'G', "rose");
    stones[2] = new Diamond( "C5427", 1.0, "VS1",  'D', "princess");
    stones[3] = new Diamond( "D8307", 1.6, "SI1",  'H', "brilliant");
    stones[4] = new Diamond( "B4825", 0.3, "I1",   'D', "rose");
    stones[5] = new Diamond( "A1844", 2.1, "VS2",  'D', "lozenge");
    stones[6] = new Diamond( "A3747", 3.1, "SI2",  'W', "baguette");
    stones[7] = new Diamond( "E6393", 2.3, "VS2",  'I', "brilliant");
    stones[8] = new Diamond( "C5619", 2.8, "VVS1", 'E', "pear");
    stones[9] = new Diamond( "E8348", 1.4, "VS2",  'G', "brilliant");
    stones[10] = new Diamond( "D2381", 1.7, "I3",   'G', "brilliant");
    stones[11] = new Diamond( "C9253", 1.3, "VS2",  'H', "baguette");
    stones[12] = new Diamond( "G3459", 2.1, "VS2",  'H', "rose");
    stones[13] = new Diamond( "B3598", 2.4, "VVS2", 'D', "pear");
    stones[14] = new Diamond( "D9836", 2.8, "IF",   'E', "princess");
    stones[15] = new Diamond( "E1046", 2.2, "FL",   'E', "rose");
    Arrays.sort( stones );
    for ( int j=0; j<stones.length; j++ )
      System.out.println( stones[j].toString() );


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