how to i convert this case to loop...please help.....

import java.util.LinkedList; import java.util.*; import java.io.*; import java.lang.*;

public class LinkedListv4 {

char question;
Scanner console = new Scanner(System.in);
LinkedList listA = new LinkedList();

public void Switchers(){

            System.out.println("| a. Append a specified elements to the list");
            System.out.println("| b. Add an element at specified index");
            System.out.println("| c. Add a new elements in front of the list");
            System.out.println("| d. Add new elements with a specified value into the list alternately");
            System.out.println("| e. Remove the first element in the list");
            System.out.println("| f. Find an element at a specified position in the list");
            System.out.println("| g. Replace the elements at a specified index");
            System.out.println("| h. Print the list");
            System.out.println("| i. Print the list from a specified index");
            System.out.println("| j. Print the list in reverse order");
            System.out.println("| k. Remove all elements in the list");
            System.out.println("| l. Check for empty list");
            System.out.println("| q. Quit");



            question = console.next().charAt(0);
            System.out.println();



            switch (question) {
              case 'a': AppendElement();

              case 'b': AddElementSpecific();

              case 'c': AddElementFront();

              case 'd': EditExistingList();

              case 'e': RemoveFirstElement();

              case 'f': ViewElements();

              case 'g': ReplaceElement();

              case 'h': PrintList();

              case 'i': PrintListSpecific();

              case 'j': PrintReverseOrder();

              case 'k': ClearAll();

              case 'l': CheckEmptyList();

              case 'q': Quit(); 

              case 'Q': Quit(); break;

              default: System.out.println("Invalid Input"); 
                        System.out.println();
                        Switchers(); break;
}

}

            //1 --- DONE
            public void AppendElement() {

                    System.out.println("+---------------------------------------------------------------------+");
                    System.out.println("| Create/Store objects in an LinkedList container.                    |");
                    System.out.println("+---------------------------------------------------------------------+");
                    System.out.println();

                    System.out.println("Please set maximum elements required");
                    System.out.println();
                    int Max = console.nextInt();

                    for (int i = 0; i < Max; i++) {

                        System.out.println("Please insert number for element "+ i);
                        double element = console.nextDouble();
                        System.out.println("  - Storing Number(" + element + ")");
                        listA.add(new Double(element));
                    }

                        System.out.println();
                        System.out.println("+---------------------------------------------------------------------+");
                        System.out.println("| Retrieve objects in an LinkedList container using an Iterator.      |");
                        System.out.println("+---------------------------------------------------------------------+");
                        System.out.println();

                        Iterator Ite = listA.iterator();
                            while (Ite.hasNext()) {
                                System.out.println(Ite.next());
                            }

                            Switchers();

            }

            //2 --- DONE FIXED - ???
            public void AddElementSpecific() {



                    System.out.println("+---------------------------------------------------------------------+");
                    System.out.println("| Create/Store objects in specified  LinkedList container.            |");
                    System.out.println("+---------------------------------------------------------------------+");
                    System.out.println();

                    System.out.println("Please insert specified index :");
                    int index = console.nextInt();

                        System.out.println("Please insert number for element  :");
                        double element = console.nextDouble();
                        System.out.println("  - Storing Number(" + element + ")");
                        listA.add(index,new Double(element));

                        System.out.println();
                        System.out.println("+---------------------------------------------------------------------+");
                        System.out.println("| Retrieve objects in an LinkedList container using an Iterator.      |");
                        System.out.println("+---------------------------------------------------------------------+");
                        System.out.println();

                        Iterator Ite = listA.iterator();
                            while (Ite.hasNext()) {
                                System.out.println(Ite.next());


                            }

                            Switchers();

                }

            //3 --- DONE
            public void AddElementFront() {

                    System.out.println("+---------------------------------------------------------------------+");
                    System.out.println("| Create/Store objects in front of LinkedList container.              |");
                    System.out.println("+---------------------------------------------------------------------+");
                    System.out.println();

                        int i= 0;
                        System.out.println("System will store element to the first index, Insert new element please  :");
                        double element = console.nextDouble();
                        System.out.println("  - Storing Number(" + element + ")");
                        listA.add(0,new Double(element));


                        System.out.println();
                        System.out.println("+---------------------------------------------------------------------+");
                        System.out.println("| Retrieve objects in an LinkedList container using an Iterator.      |");
                        System.out.println("+---------------------------------------------------------------------+");
                        System.out.println();

                        Iterator Ite = listA.iterator();
                            while (Ite.hasNext()) {
                                System.out.println(Ite.next());


                            }

                            Switchers();
                }

            //4 --- DONE - ???
            public void EditExistingList() {

                    System.out.println("+---------------------------------------------------------------------+");
                    System.out.println("| Add new elements with a specified value into the list alternately   |");
                    System.out.println("+---------------------------------------------------------------------+");
                    System.out.println();
                    System.out.println();
                    System.out.println("+---------------------------------------------------------------------+");
                    System.out.println("| Retrieve objects in an LinkedList container using an Iterator.      |");
                    System.out.println("+---------------------------------------------------------------------+");
                    System.out.println();
                    Iterator IteInitial = listA.iterator();
                            while (IteInitial.hasNext()) {
                                System.out.println(IteInitial.next());
                            }

                    System.out.println("Please choose desirable index to modify elements");
                    System.out.println();
                    int SpecIndex = console.nextInt();
                    listA.remove(SpecIndex);

                        System.out.println("Please insert new number for element "+ SpecIndex);
                        double element = console.nextDouble();
                        System.out.println("  - Storing Number(" + element + ")");
                        listA.add(SpecIndex,new Double(element));

                        System.out.println();
                        System.out.println("+---------------------------------------------------------------------+");
                        System.out.println("| Retrieve objects in an LinkedList container using an Iterator.      |");
                        System.out.println("+---------------------------------------------------------------------+");
                        System.out.println();

                        Iterator Ite = listA.iterator();
                            while (Ite.hasNext()) {
                                System.out.println(Ite.next());
                            }

                            Switchers();                        

                }

            //5 --- DONE
            public void RemoveFirstElement() {

                    System.out.println("+---------------------------------------------------------------------+");
                    System.out.println("|      Remove fisrt element in the LinkedList container.              |");
                    System.out.println("+---------------------------------------------------------------------+");
                    System.out.println();

                    Object object = listA.removeFirst();
                    System.out.println(object + " has been removed from the first index of LinkedList");

                    System.out.println();
                    System.out.println("+---------------------------------------------------------------------+");
                    System.out.println("| Retrieve objects in an LinkedList container using an Iterator.      |");
                    System.out.println("+---------------------------------------------------------------------+");
                    System.out.println();

                    Iterator Ite = listA.iterator();
                    while (Ite.hasNext()) {
                    System.out.println(Ite.next());


                            }

                            Switchers();

                }

            //6 --- DONE
            public void ViewElements() {

                    System.out.println("+---------------------------------------------------------------------+");
                    System.out.println("| Find an element at a specified position in the list                 |");
                    System.out.println("+---------------------------------------------------------------------+");
                    System.out.println();
                    System.out.println();
                    System.out.println("+---------------------------------------------------------------------+");
                    System.out.println("| Retrieve objects in an LinkedList container using an Iterator.      |");
                    System.out.println("+---------------------------------------------------------------------+");
                    System.out.println();

                    Iterator Ite = listA.iterator();
                    while (Ite.hasNext()) {
                    System.out.println(Ite.next());
                    }

                    System.out.println("Select any element in the list to review index position :");
                    double element = console.nextDouble();
                    System.out.println();

                    int NotNegOne = listA.indexOf(element);

                    if (NotNegOne != -1) {
                      System.out.println("element "+element+" is at index "+listA.indexOf(element));
                    } 

                    else {
                      System.out.println("LinkedList does not contain "+element);
                    }

                    Switchers();

                }


            //7 --- DONE
            public void ReplaceElement() {

                    System.out.println("+---------------------------------------------------------------------+");
                    System.out.println("| Replace the elements at a specified index                           |");
                    System.out.println("+---------------------------------------------------------------------+");
                    System.out.println();
                    System.out.println();
                    System.out.println("+---------------------------------------------------------------------+");
                    System.out.println("| Retrieve objects in an LinkedList container using an Iterator.      |");
                    System.out.println("+---------------------------------------------------------------------+");
                    System.out.println();
                    Iterator IteInitial = listA.iterator();
                            while (IteInitial.hasNext()) {
                                System.out.println(IteInitial.next());
                            }

                    System.out.println();
                    System.out.println("Please choose desirable index to modify elements");
                    System.out.println();
                    int SpecIndex = console.nextInt();
                    listA.remove(SpecIndex);

                        System.out.println("Please insert new number for index "+ SpecIndex);
                        double element = console.nextDouble();
                        System.out.println("  - Storing Number(" + element + ")");
                        listA.add(SpecIndex,new Double(element));

                        System.out.println();
                        System.out.println("+---------------------------------------------------------------------+");
                        System.out.println("| Retrieve objects in an LinkedList container using an Iterator.      |");
                        System.out.println("+---------------------------------------------------------------------+");
                        System.out.println();

                        Iterator Ite = listA.iterator();
                            while (Ite.hasNext()) {
                                System.out.println(Ite.next());
                            }

                    Switchers();

                }

            //8 --- DONE
            public void PrintList() {

                    System.out.println("+---------------------------------------------------------------------+");
                    System.out.println("|      Print List in the LinkedList container.                    |");
                    System.out.println("+---------------------------------------------------------------------+");
                    System.out.println();

                    if (listA.isEmpty()){
                    System.out.println("Linked list is empty");
                    }
                    else{
                     System.out.println (listA);
                    }

                    Switchers();

                }

            //9 --- DONE
            public void PrintListSpecific() {

                                    System.out.println("+---------------------------------------------------------------------+");
                    System.out.println("|      Print List from specified index in the LinkedList container.   |");
                    System.out.println("+---------------------------------------------------------------------+");
                    System.out.println();

                    try {

                    int indexSize = listA.size();
                    int realIndexSize = indexSize - 1;
                    System.out.println("Total Index in LinkedList (counting from O) "+realIndexSize);
                    System.out.println();
                    System.out.println();
                    System.out.println("Please choose desirable index to view its element");
                    System.out.println();
                    int SpecIndex = console.nextInt();
                    System.out.println();
                    System.out.println("The element is "+listA.get(SpecIndex)+" at index "+SpecIndex);

                    }

                    catch ( Exception e )  {
                        System.out.println();
                        System.out.println("LinkedList does not contain index requested");  
                    }


                    Switchers();

                }

            //10 --- DONE
            public void PrintReverseOrder() {

                    System.out.println();
                    System.out.println("+---------------------------------------------------------------------+");
                    System.out.println("| Reverse the list in the LinkedList container.                       |");
                    System.out.println("+---------------------------------------------------------------------+");
                    System.out.println();

                    ListIterator itr = listA.listIterator();

                    System.out.println("Iterating through elements of Java LinkedList using ListIterator in forward direction...");
                    while(itr.hasNext())
                    {
                    System.out.println(itr.next());
                    }

                    System.out.println("Iterating through elements of Java LinkedList using ListIterator in reverse direction...");
                    while(itr.hasPrevious())
                    {
                    System.out.println(itr.previous());
                    }


            Switchers();

                }

            //11 --- DONE
            public void ClearAll() {

                System.out.println("+---------------------------------------------------------------------+");
                System.out.println("|      Clear entire LinkedList                                        |");
                System.out.println("+---------------------------------------------------------------------+");
                System.out.println();

                listA.clear();
                System.out.println("All element has been removed");
                System.out.println();
                System.out.println();

                if (listA.isEmpty()){
                    System.out.println("Linked list is empty");
                    }
                    else{
                     System.out.println (listA);
                    }

                Switchers();

                }

            //12 --- DONE
            public void CheckEmptyList() {

                if (listA.isEmpty()){
                    System.out.println();
                    System.out.println("Linked list is empty");
                    System.out.println();
                    }
                    else{
                     System.out.println (listA);
                    }

                Switchers();

                }

            //13 ---DONE
            public void Quit() {

                System.exit(0);
                }


public static void main (String args[]) {

    LinkedListv4 MYlinkList = new LinkedListv4();
    MYlinkList.Switchers();
}

}

September 19, 2011 at 11:14 AM

Do modifications in Switchers() method:

public void Switchers(){
              boolean exit=false;
              do{
            System.out.println("| a. Append a specified elements to the list");
            System.out.println("| b. Add an element at specified index");
            System.out.println("| c. Add a new elements in front of the list");
            System.out.println("| d. Add new elements with a specified value into the list alternately");
            System.out.println("| e. Remove the first element in the list");
            System.out.println("| f. Find an element at a specified position in the list");
            System.out.println("| g. Replace the elements at a specified index");
            System.out.println("| h. Print the list");
            System.out.println("| i. Print the list from a specified index");
            System.out.println("| j. Print the list in reverse order");
            System.out.println("| k. Remove all elements in the list");
            System.out.println("| l. Check for empty list");
            System.out.println("| q. Quit");


            System.out.print("Enter your choice: ");
            question = console.next().charAt(0);
            System.out.println();



            switch (question){
              case 'a': AppendElement();
                        break;

              case 'b': AddElementSpecific();
                        break;

              case 'c': AddElementFront();
                        break;

              case 'd': EditExistingList();
                        break;

              case 'e': RemoveFirstElement();
                        break;

              case 'f': ViewElements();
                        break;

              case 'g': ReplaceElement();
                        break;

              case 'h': PrintList();
                        break;

              case 'i': PrintListSpecific();
                        break;

              case 'j': PrintReverseOrder();
                        break;

              case 'k': ClearAll();
                        break;

              case 'l': CheckEmptyList();
                        break;

              case 'q': Quit();
                        exit=true;
                        break;

              case 'Q': Quit();
                        exit=true;
                        break;

              default: System.out.println("Invalid Input"); 
                        System.out.println();
                         break;

}
              }
              while(!exit);

}