August 1999
JP219 : JAVA PROGRAMMING

QUESTION 3

Total Marks: 20 Marks

• Question 1
• Question 2
• Question 4
• Question 5
• Cover Page

SUGGESTED SOLUTIONS
Solutions and allocated marks are indicated in green.
Return to Question 3

• a mild error condition
• which disturbs the normal flow of execution of a program.

• The program attempts to open a file which does not exist;
• The network connection is disrupted;
• Operands are out of prescribed ranges;
• Attempting to load a missing class files.

• defines mild error conditions that the program may encounter;
• and how the program should deal with them.

• defines more serious error conditions;
• which the program should not usually attempt to recover from.

public class OutOfRange extends Exception {
   private String reason;
   public OutOfRange(String reason) {
   this. reason = reason ;
}

public String GetReason() {
   return reason ;
  }

}

(i) Give the definition of a Java class, called MyClass which will contain a constructor function taking two integer parameters a and b, and a String returning function Foo, which is capable of throwing an exception of type OutOfRange.

(ii) Using the Java keyword throw, define the member function Foo such that it will throw the exception OutOfRange if and only if param is equal to or greater than limit, with the string message "parameter out of range".

(iii) Using the keyword try and catch, implement the constructor function such that it will try to ensure a is b, and will catch the exception, printing out the reason if it is not.

[4]

[4]

[4]

public class MyClass {
    MyClass (int a, int b);
    Foo (int param, int limit) throws OutOfBounds;
}

public Foo (int param, int limit) throws OutOfBounds {
   if (param >= limit)
      throw new OutOfBounds (' 'parameter out of range' ');
}

public MyClass (int a, int b) {
   try{
     Foo(a,b);
    }  catch (OutOfBounds E)  {
        System.out.printIn (E.getReason( ) );
    }
}