This advanced control material is drawn from earlier chapters in the text.

Reading:

• Chapter 5, Section 5.4
• Chapter 7, Section 7.6

5.4. Switch statements

Consider the following code segments. Can you effectively re-write them using a switch statement? If so demonstrate how and consider whether the switch -based version is better or worse than the if -based version version. If not, explain why not.

• The following code segment converts an integer entered by the user into a word, e.g., it converts 1 to “one”.

  Scanner keyboard = new Scanner(System.in);
  
  System.out.print("Enter a digit between 0 and 4: ");
  int x = keyboard.nextInt();
  
  if (x == 0) {
  	System.out.println("zero");
  } else if (x == 1) {
  	System.out.println("one");
  } else if (x == 2) {
  	System.out.println("two");
  } else if (x == 3) {
  	System.out.println("three");
  } else if (x == 4) {
  	System.out.println("four");
  } else {
  	System.out.println("invalid input...");
  }
  

• The following code segment converts a word entered by the user into a digit, e.g., it converts “one” to 1.

  System.out.print("Enter a digit name (i.e., one, two, ..., four): ");
  String number = keyboard.next();
  
  if (number.equalsIgnoreCase("zero")) {
  	System.out.println(0);
  } else if (number.equalsIgnoreCase("one")) {
  	System.out.println(1);
  } else if (number.equalsIgnoreCase("two")) {
  	System.out.println(2);
  } else if (number.equalsIgnoreCase("three")) {
  	System.out.println(3);
  } else if (number.equalsIgnoreCase("four")) {
  	System.out.println(4);
  } else {
  	System.out.println("invalid input...");
  }
  

7.6. Recursion

Try converting the factorial function shown in the text into a similar summation function, that is computeSummation(n) returns:

1 + 2 + ... + n.

Yes, we know that this can be computed without repetition using n(n-1)/2 , but pretend that you don’t know that!