Chapter 20, Problem 2PC

Program Plan Intro

Linked List Sorting and Reversing

Program Plan:

For filename: Modified “LinkedList1.java”

• In this class, additionally need to add two methods “sort()” and “reverse()”.
• Define the method “sort()” which is used to sort the elements in the list by alphabetical order.
  • Create two variables “current_node” and “index_value” using “Node” class and this variable set to “null”.
  • Declare a string variable “temp_value”.
  • Check whether list is empty. If the list is empty, then returns nothing.
  • Otherwise,
    • Check condition using “for” loop. That is the current node will point to first.
      • Check the condition using “for” loop that is for index value will point to next node of current node.
        • If data in the “current_node” is greater than the data in “index_value”, then swap the data of “current_node” and “index_index”.
• Define the method “reverse()” which is used to reverse the elements in the list.
  • Create a list “rev_list” and set it to “null”.
  • Performs “while” loop. This loop will perform up to the first node equals to “null”.
    • Set a reference “ref” to first node.
    • Set “first” to next first node.
    • Set next node to “rev_list”.
    • Set the “rev_list” to reference “ref”.
  • Make the list “rev_list” as the new list.

For filename: “LinkedList1Demo.java”:

• Import required package.
• Define “LinkedList1Demo” class.
  • Create an instance for “LinkedList1” class, text area, command text field, and result text field.
  • Define constructor for “LinkedList1Demo()” class.
    • Create instance.
    • Create a panel for “Command Result” text field.
    • Create a label for command result.
    • Place the text area in center of the frame.
    • Create a panel and label for “Command” text field.
    • Set up the frame.
  • Define private class “commandTextListener” that reply to the user entered command.
    • Define “actionPerformed” class.
      • Read the command from the command text field.
      • Create an object for “Scanner” class.
      • Read command from user.
      • Check the user entered command using “switch” statement.
        • If the user entered command is “sort”, then,
        • • Sort the linked list “new_list” by calling the method “sort()”.
          • Displays lists in alphabetical order.
          • Assign a status message for the “sort” command was finished.
          • Displays status message to “Command Result” text field.
        • If the user entered command is “reverse”, then
        • • Reverse the linked list “new_list” by calling the method “reverse()”.
          • Prints the reversed list.
          • Assign a status message for the “reverse” command was finished.
          • Displays status message to “Command Result” text field.
        • If the user entered command is “add”, then
        • • Check condition. If it is true, then
            • Read index and string element from user.
            • Add that index and its element to linked list “new_list” by calling the method “add”.
          • Otherwise,
            • Read string element from user.
            • Add string element to the list “new_list” by calling the method “add”.
          • Display the added string elements.
        • If the user entered command is “remove”, then
        • • Check condition. If it is true, then
            • Read an index from user.
            • Remove an element at given index.
            • Display the removed element at given index to “Command Result” text field.
          • Otherwise,
            • Read an element from the list.
            • Obtain the Boolean result.
            • Convert the Boolean into string.
            • Display the Boolean result to “Command Result” text field.
          • Displays string elements in the list
        • If the user entered command is “isEmpty”, then
        • • Check the given list is empty or not by calling the method “isEmpty” and store the result in “result_text3”.
          • Display the result to “Command Result” text field.
        • If the user entered command is “size”, then
        • • Compute the size of list “new_list” by calling the method “size()” and store the result in “result_text4”.
          • Display the result to “Command Result” text field.
  • Define main function.
    • The instance of “LinkedList1Demo” class displays its window.