Directions: Give brief but precise answers to the following questions; ask if you have a question.

• Name and describe the three characteristics of object-oriented languages? (6 pts)

encapsulation - grouping related data and the methods which operate on that data

inheritance - inheriting classes get base class fields and methods automatically

polymorphism - correct like-named method chosen for related objects (see #9)

• Name and describe precisely the four Java access specifiers. (8 pts)

public - accessible from anywhere (from any package)

package (or friendly) - accessible from within package

protected - accessible from any inherited class or within package

private - accessible only within class

• Describe precisely the difference between array definitions in C++ and Java. (5 pts)

arrays in C++ may be defined statically (compile time) or dynamically (run time - via new); arrays in Java are objects and must be defined dynamically (via new); Java arrays of objects need double allocation (one for array of handles and one for array objects); Java arrays of primitives need only a single allocation

• Describe the Java concept of packages. (3 pts)

packages are a method of grouping classes for name scoping

• Describe the difference between early and late binding. (3 pts)

early binding occurs during compilation while late binding occurs during execution

• Write a "Hello, Java!" application which is contained in the file Hello.java. (10 pts)

public class Hello { // 2 pts

public static void main(String[] args) { // 4 pts

System.out.println("Hello, Java!"); // 2 pts

} // 1 pt

} // 1 pt

• Write a Java class called Base and another Java class called Derived. Using a package called Separate as needed, place the four integer fields called global, inherited, local, and friendly in the two classes such that there are four different scopes. (15 pts)

public class Base { // +1 pt

public int global; // +2 pts

protected int inherited; // +2 pts

private int local; // +2 pts

} // + 1 pt

package Separate; // + 1 pt

public class Derived extends Base { // + 3 pts

int friendly; // + 2 pts

} // + 1 pt

• Write a Wrestling class (a type of Athlete class) which has integer fields called pins, wins, and losses. The class should have a single constructor with four parameters, get and set accessors, a toString method, and a evaluate method. The evaluate method returns (((2 * (pins / wins)) + (1 * (wins / (wins + losses)))) / 3) * 100. (25 pts)

// Wrestling.java by Dr. I. for CS 102 during Spring, 1999

// This is question #8 on exam #2

public class Wrestling extends Athlete { // +2 pts

public Wrestling(String name, int pins,

int wins, int losses) { // +5 pts

super(name);

setPins(pins); setWins(wins); setLosses(losses);

}

public int getPins() { return pins; } // +3 pts

public int getWins() { return wins; }

public int getLosses() { return losses; }

public int evaluate() { // +4 pts

return (int) (((2.0 * ((double)pins / (double)wins)) +

(1.0 * ((double)wins /

((double)wins + (double)losses)))

) / 3.0 * 100.0);

}

public String toString() { // +4 pts

return super.toString() + ",pins(" + pins +

"),wins(" + wins + "),losses(" + losses + ")";

}

private void setPins(int pins) { this.pins = pins; }

private void setWins(int wins) { this.wins = wins; }

private void setLosses(int losses)

{ this.losses = losses; } // +3 pts

private int pins; // +3 pts

private int wins;

private int losses;

} // +1 pt

• Define an Athlete array called athletes of MAX_ATHLETE elements and allocate one Wrestling object and two objects of your group. Then show polymorphism while outputting the object, the string " has a value of ", and its evaluate value. (15 pts)

Athlete[] athletes = new Athlete[MAX_ATHLETE]; // + 3 pts

athletes[0] = new Wrestling("name1", 15, 20, 2); // + 3 pts

athletes[1] = new Sport("name2", ...); // + 3 pts

athletes[2] = new Sport("name3", ...); // + 2 pts

for (int athlete = 0; athlete < 3; ++athlete) { // + 1 pt

System.out.println(athletes[athlete] + // + 3 pts

" has a value of " +

athletes[athlete].evaluate();

}

• Write just the code (no method necessary) to input the value of inputValue like shown in class. Define and use the values buffer and/or string if needed. (10 pts)

Byte[] buffer = new Byte[80]; // + 2 pts

try { // + 1 pt

System.in.read(buffer); // + 2 pts

}

catch (IOException ioe) { // +1 pt

System.out.println("Error in read");

}

String string = new String(buffer); // + 2 pts

int inputValue = new Integer(string.trim()).intValue();

// + 2 pts