COP 2800 (Java Programming I) Homework Assignment #3

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 class?

   public class Test {
       public static void method ( int x ) {
       }
       public static int method ( int y ) {
           return y;
       }
   }

6. 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 (inclusive) and 55.5 (exclusive).
   4. Write an expression that obtains a random lowercase (English) letter.
7. 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
       }
   }

8. 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();
9. 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;
   }
   }

10. 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();
11. 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?

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