Penggunaan Linked List Pada Java

picture from https://chercher.tech/kotlin/linked-list-kotlin

Linked list merupakan salah satu jenis struktur data linier yang terdiri dari sekumpulan data dengan tipe yang sama dimana masing-masing data terikat dengan satu data lainnya, sehingga membentuk seperti sebuah rantai satu arah. Linked list bersifat dinamis, artinya kita dapat menambah data sebanyak yang kita mau tanpa harus dibatasi ukuran. Hal ini berbeda dengan array biasa, yang mana ketika pertama kali diinisialisasi, pasti harus mencantumkan size-nya terlebih dahulu, yang berarti kita tidak bisa menambahkan elemen array lebih dari batas yang sudah ditentukan. Berikut ini merupakan salah satu program yang menggunakan fitur linked list pada java.

	package assignment_06;

	import java.util.*;

	/**
	* This class represents application that show how
	* {@link LinkedList} is implemented
	*
	* @author Fajar Zuhri Hadiyanto
	* @version 1.0
	* @since 28th April 2021
	* */
	public class LinkedListApplication {

	/**
	* Static field to contain all function with {@link Integer} key
	* to represent function order in the app menu, then {@link Function}
	* as a value
	* */
	private static HashMap<Integer, Function> functions;

	/** Static field to contain the main data of this application */
	private static LinkedList<String> data;

	/**
	* This static class represents function object
	* */
	static class Function {

	/**
	* Field to contain string representation of function as
	* function name to be shown in the app menu
	* */
	private final String name;

	/** Field to contain function to be executed */
	private final Runnable function;

	/**
	* This construction is used to initialize {@link Function} object
	*
	* @param name {@link String} representation of the function object
	* @param function {@link Runnable} object of function to be executed
	* */
	Function(String name, Runnable function) {
	this.name = name;
	this.function = function;
	}

	/**
	* This method is used to get the name of the function
	*
	* @return field {@link #name}
	* */
	public String getName() {
	return this.name;
	}

	/**
	* This method is used to run the {@link #function} field
	* */
	void run() {
	this.function.run();
	}
	}

	/**
	* This method is used to initialize the app
	* by initialize the main data and configure all
	* possible function to be executed in the app
	* */
	private static void initApp() {
	data = new LinkedList<>();
	functions = new HashMap<>();
	functions.put(1, new Function("Add Data", LinkedListApplication::addData));
	functions.put(2, new Function("Add Data at First", LinkedListApplication::addDataToFirst));
	functions.put(3, new Function("Add Data at Last", LinkedListApplication::addDataToLast));
	functions.put(4, new Function("Add Data at N Index", LinkedListApplication::addDataAtLocation));
	functions.put(5, new Function("Remove Data at N Index", LinkedListApplication::removeData));
	functions.put(6, new Function("Remove Data at First", LinkedListApplication::removeDataAtFirst));
	functions.put(7, new Function("Remove Data at Last", LinkedListApplication::removeDataAtLast));
	functions.put(8, new Function("Remove Data by Data Content", LinkedListApplication::removeDataByContent));
	functions.put(9, new Function("Program Exit", LinkedListApplication::programExit));
	}

	/**
	* This method is used as main method
	*
	* @param args arguments to the console app while compiled and launched.
	* */
	public static void main(String[] args) {

	initApp();
	programMenu();

	}

	/**
	* This is a utility method to get a new {@link Scanner} object
	*
	* @return new {@link Scanner} object
	* */
	private static Scanner scanner() {
	return new Scanner(System.in);
	}

	/**
	* This is a utility method to prompt an integer data and return that value.
	* This method will reprompt if the input is not an integer.
	*
	* @param message prompt message to be shown
	* @return int data inputted by user
	* */
	private static int promptInt(String message) {
	int value;
	while(true) {
	System.out.print(message);
	try {
	value = scanner().nextInt();
	return value;
	} catch(InputMismatchException e) {
	System.out.println("Input must be an integer!");
	}
	}
	}

	/**
	* This is a utility method to prompt a string data and return that value
	*
	* @param message prompt message to be shown
	* @return string data inputted by user
	* */
	private static String promptString(String message) {
	System.out.print(message);
	return scanner().nextLine();
	}

	/**
	* This is a utility method to display current value of {@link #data}
	* */
	private static void displayData(){
	System.out.println("----------\| Current Data \|----------");
	System.out.println("Data in the list : " + data);
	System.out.println("Total Data : " + data.size());
	System.out.println("------------------------------------");
	}

	/**
	* This method is used to insert the data by default (at last).
	* */
	private static void addData() {
	String tempData = promptString("Input the data to be inserted: ");
	data.add(tempData);
	displayData();
	}

	/**
	* This method is used to insert the data at a certain index.
	* */
	private static void addDataAtLocation() {
	displayData();
	int indexData = promptInt("Input index of data to be inserted by new data: [0 - " + (data.size() - 1) + "]: ");
	String tempData = promptString("Data to be inserted at index " + indexData + ": ");
	data.add(indexData, tempData);
	displayData();
	}

	/**
	* This method is used to insert the data at first.
	* */
	private static void addDataToFirst() {
	String tempData = promptString("Input the data to be inserted at first: ");
	data.addFirst(tempData);
	displayData();
	}

	/**
	* This method is used to insert the data at last.
	* */
	private static void addDataToLast() {
	String tempData = promptString("Input the data to be inserted at last: ");
	data.addLast(tempData);
	displayData();
	}

	/**
	* This method is used to find out if some value is in the main data.
	*
	* @return {@code true} if main data contains given value, else {@code false}
	* */
	private static boolean searchData(String value) {
	return data.contains(value);
	}

	/**
	* This method is used to remove data by index.
	* */
	private static void removeData() {
	displayData();
	int indexData = promptInt("Input index of data to be deleted: [0 - " + (data.size() - 1) + "]: ");
	data.remove(indexData);
	displayData();
	}

	/**
	* This method is used to remove data at first.
	* */
	private static void removeDataAtFirst() {
	data.removeFirst();
	displayData();
	}

	/**
	* This method is used to remove data at last.
	* */
	private static void removeDataAtLast() {
	data.removeLast();
	displayData();
	}

	/**
	* This method is used to remove data by it's content
	* */
	private static void removeDataByContent() {
	displayData();
	String value = promptString("Input data to be deleted: ");

	if(searchData(value))
	data.remove(value);
	else
	System.out.println("Please input data which is in the list !");

	displayData();
	}

	/**
	* This method is used to exit the application.
	* */
	private static void programExit() {
	System.exit(0);
	}

	/**
	* This method is used to display the program menu.
	* */
	private static void programMenu() {
	System.out.println("==========\| PROGRAM MENU \|==========");

	for (Map.Entry<Integer, Function> fun: functions.entrySet()) {
	System.out.println(fun.getKey() + ". " + fun.getValue().getName());
	}
	programSwitcher();
	}

	/**
	* This method is used to get menu index inputted by user
	* then, run the corresponding function.
	* */
	private static void programSwitcher() {
	int indexMenu = promptInt("Choose Menu [1 - 9]: ");

	if (1 <= indexMenu && indexMenu <= 9)
	functions.get(indexMenu).run();

	programMenu();
	}
	}