COP 2800 (Java Programming I) Homework Assignment #3

 

Due: by the start of class on the date shown on the syllabus

Description:

Answer the following questions as briefly (but completely) as possible:

  1. How do you simplify the max method in the following, using the conditional operator?
        /** Return the max of two numbers */
        public static int max ( int num1, int num2 ) {
            int result;
    
            if ( num1 > num2 )
                result = num1;
            else
                result = num2;
            return result;
        }
  2. Write method headers (just the declaration, not the bodies) for the following methods:
    1. Compute a sales commission, given the sales amount and the commission rate.
    2. Display the calendar for a month, given the month and year.
    3. Compute a square root of a number.
    4. Test whether a number is even, and returning true if it is.
    5. Display a message a specified number of times.
    6. Compute the monthly payment, given the loan amount, number of years, and annual interest rate.
    7. Find the corresponding uppercase letter, given a lowercase letter.
  3. Identify and correct the errors in the following program:
    public class Test {
        public static method1(int n, m) {
            n += m;
            method2 (3. 4);
        }
    
        public static int method2(int n) {
            if ( n > 0 ) return 1;
            else if (n == 0) return 0;
            else if (n < 0) return -1;
        }
    }
  4. What is pass-by-value?  Show the results of the following two programs.
    1. public class Test {
          public static void main ( String [] args ) {
              int max = 0;
              max(1, 2, max);
              System.out.println(max);
          }
      
          public static void max ( int value1, int value2, int max ) {
              if ( value1 > value2 )
                  max = value1;
              else
                  max = value2;
          }
      }
    2. public class Test {
          public static void main ( String [] args ) {
              int i = 1;
              while ( i <= 6 ) {
                  method1( i, 2 );
                  i++;
              }
          }
      
          public static void method1 ( int i, int num ) {
              for ( int j = 1; j <= i; j++ ) {
                  System.out.print( num + " " );
                  num *= 2;
              }
              System.out.println();
          }
      }
  5. What is wrong with the following program?
    public class Test {
        public static void method ( int x ) {
        }
        public static int method ( int y ) {
            return y;
        }
    }
    1. Write an expression that obtains a random integer between 34 and 55, inclusive.
    2. Write an expression that obtains a random integer between 0 and 999, inclusive.
    3. Write an expression that obtains a random number between 5.5 and 55.5, inclusive.
    4. Write an expression that obtains a random lowercase (English) letter.
  6. How many times is the factorial method in the following invoked, for the call factorial(6)?
    import java.util.Scanner;
    
    public class ComputeFactorial {
        public static void main ( String [] args ) {
            Scanner input = new Scanner( System.in );
            System.out.print( "Enter a nonnegative integer: " );
            int n = input.nextInt();
    
            // Display factorial
            System.out.println( "Factorial of " + n + " is " + factorial(n) );
        }
    
        /** Return the factorial for the specified number */
        public static long factorial ( int n ) {
            if ( n == 0 ) // Base case
                return 1;
            else
                return n * factorial( n - 1 ); // Recursive call
        }
    }
  7. Suppose that the class F is defined as shown below.  Let f be an instance of F.  Which of the following statements are syntactically correct?
    public class F {
      int i;
      static String s;
      void iMethod () {
      }
      static void sMethod () {
      }
    }
    1. System.out.println(f.i);
    2. System.out.println(f.s);
    3. f.iMethod();
    4. f.sMethod();
    5. System.out.println(F.i);
    6. System.out.println(F.s);
    7. F.iMethod();
    8. F.sMethod();
  8. Add the static keyword in the place of ?, if appropriate, in the code below.
    public class Test {
        private int count;
        public ? void main ( String [] args ) {
            ...
        }
        public ? int getCount () {
            return count;
    }
    public ? int factorial ( int n ) {
        int result = 1;
        for ( int i = 1; i <= n; i++ )
            result *= i;
        return result;
    }
    }
  9. Can each of the following statements be compiled?
    1. Integer i = new Integer("23");
    2. Integer i = new Integer(23);
    3. Integer i = Integer.valueOf("23");
    4. Integer i = Integer.parseInt("23", 8);
    5. Double d = new Double();
    6. Double d = Double.valueOf("23.45");
    7. int i = (Integer.valueOf("23")).intValue();
    8. double d = (Double.valueOf("23.4")).doubleValue();
    9. int i = (Double.valueOf("23.4")).intValue();
    10. String s = (Double.valueOf("23.4")).toString();
    1. How do you convert an integer into a string?
    2. How do you convert a numeric string into an integer?
    3. How do you convert a double number into a string?
    4. How do you convert a numeric string into a double value?
  10. What is NullPointerException?
  11. Which of the following statements (if any) will throw an exception?  If no exception is thrown, what is the output?
    System.out.println( 1 / 0 );
    System.out.println( 1.0 / 0 );
  12. Point out the problem in the following code.  Does the code throw any exceptions?
    long value = Long.MAX_VALUE + 1;
    System.out.println( value );
  13. What is a checked exception, and what is an unchecked exception?

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