Hey there! Welcome to ClearUrDoubt.com. In this post, we will look at the Custom implementation of the Doubly LinkedList class in Java. Before proceeding further, please go through the below post for a better understanding of Doubly LinkedList. Custom Implementation of Read more
Hey there! Welcome to ClearUrDoubt.com. In this post, we will look at the Custom implementation of the Singly LinkedList class in Java. Simple implementation of Singly LinkedList:
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package com.clearurdoubt.impl; /** * * @author Sai Gowtham Badvity * SinglyLinkedList Implementation * @param <T> type of the object LinkedList holds. * */ public class MySinglyLinkedList<T> { private class Node { T value; Node next; } private Node head = null, tail = null; /** * Add Node to the List * @param val */ public void add(T val) { addLast(val); } /** * Add Node in the beginning the List * @param val */ public void addFirst(T val) { Node newNode = new Node(); newNode.value = val; newNode.next = head; head = newNode; if(tail == null) tail = newNode; } /** * Add Node at the end of the List * @param val */ public void addLast(T val) { if(head == null) { addFirst(val); return; } Node newNode = new Node(); newNode.value = val; newNode.next = null; tail.next = newNode; tail = newNode; } /** * Remove first node */ public void removeFirst() { if(head == null) return; else { head = head.next; } } /** * Remove last node */ public void removeLast() { Node temp = head; while(temp.next != tail) { temp = temp.next; } temp.next = null; tail = temp; } /** * Print the elements */ @Override public String toString() { StringBuilder builder = new StringBuilder(); Node temp = head; do { builder.append( temp.value + " -> "); temp = temp.next; } while(temp.next != null); builder.append( temp.value ); return builder.toString(); } } |
Let’s see the demo of MySinglyLinkedList class:
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package com.clearurdoubt.impl; /** * * @author Sai Gowtham Badvity * Demo of the usage of MySinglyLinkedList * */ public class MySinglyLinkedListDemo { public static void main(String[] args) { MySinglyLinkedList<Integer> myList = new MySinglyLinkedList<Integer>(); myList.add(10); myList.add(20); myList.add(30); myList.addFirst(40); myList.addLast(50); System.out.println(); System.out.println("Elements in the list: " + myList); myList.removeFirst(); System.out.println(); System.out.println("After removing first node: " + myList); myList.removeLast(); System.out.println(); System.out.println("After removing last node: " + myList); myList.addFirst(40); System.out.println(); System.out.println("After adding a new node in the beginning: " + myList); } } |
Output: Happy Learning :). Read more
Hey there! Welcome to ClearUrDoubt.com. In this post, we will look at the Custom implementation of the ArrayList class in Java. Custom ArrayList Implementation:
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package com.clearurdoubt; import java.util.Arrays; public class MyArrayList { private Object[] arrayObjs; private int idx; // Constructors public MyArrayList() { this(10); } public MyArrayList(int initialcapacity) { arrayObjs = new Object[initialcapacity]; } /** * * @return size of the List */ public int size() { return idx; } /** * * @param index * @return status of the operation */ public boolean add(Object obj) { return add(idx, obj); } /** * * @param index of the new object * @param obj to be added to the List * @return status of the operation */ public boolean add(int index, Object obj) { // check for the index out of bounds condition if(index < 0 || index > idx) { throw new ArrayIndexOutOfBoundsException(); } // increase the size of the list if idx reaches the maximum limit if(idx > arrayObjs.length - 1) { increaseSize(); } if(index < idx) { // Prior to inserting the new element, move all the elements to next positions for(int temp = idx+1; temp > index; temp--) { arrayObjs[temp] = arrayObjs[temp-1]; } // insert the element arrayObjs[index] = obj; // as the new element is added, increment the idx value. idx++; } else { // insert the element at the idx position arrayObjs[idx++] = obj; } return true; } /** * * @param obj * @return status of the operation */ public boolean remove(Object obj) { // Find the index of the obj in the array and call remove(index) method for(int i = 0; i < idx; i++) { if(arrayObjs[i].equals(obj)) { return remove(i); } } return true; } /** * * @param index * @return status of the operation */ public boolean remove(int index) { if(index < 0 || index > idx) { throw new ArrayIndexOutOfBoundsException(); } for(int i = index; i < idx - 1; i++) { arrayObjs[i] = arrayObjs[i+1]; } // as the new element is deleted, decrement the idx value. arrayObjs[idx-1] = null; idx--; return true; } private void increaseSize() { int newcapacity = (arrayObjs.length * 3/2) + 1; arrayObjs = Arrays.copyOf(arrayObjs, newcapacity); } @Override public String toString() { StringBuilder sb = new StringBuilder(); for(int i = 0; i < idx; i++) { sb.append(arrayObjs[i].toString() + ","); } return "[" + sb.toString().substring(0, sb.length() - 1) + "]"; } } |
Let’s see the demo of MyArrayList class:
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package com.clearurdoubt; public class MyArrayListDemo { public static void main(String[] args) { MyArrayList myAL = new MyArrayList(); // add elements to the List myAL.add("A"); myAL.add("B"); myAL.add("C"); System.out.println(myAL + " @@@ " + myAL.size()); // print elements and size myAL.add(1, "D"); myAL.add(2, "E"); System.out.println(myAL + " @@@ " + myAL.size()); // print elements and size myAL.add(5, "F"); System.out.println(myAL + " @@@ " + myAL.size()); // print elements and size for(int i = 0; i < 10; i++) { myAL.add(i); } System.out.println(myAL + " @@@ " + myAL.size()); // print elements and size // Lets check the remove operations // remove the object myAL.remove("F"); System.out.println("After removing \"F\": "); System.out.println(myAL + " @@@ " + myAL.size()); // print elements and size // remove the object at index myAL.remove(5); System.out.println("After removing element at index 5: "); System.out.println(myAL + " @@@ " + myAL.size()); // print elements and size // remove element which is not in the ArrayList myAL.remove("F"); System.out.println("After removing \"F\": "); System.out.println(myAL + " @@@ " + myAL.size()); // print elements and size // remove last element in the ArrayList myAL.remove(new Integer(9)); System.out.println("After removing \"9\": "); System.out.println(myAL + " @@@ " + myAL.size()); // print elements and size try { myAL.add(40, "Z"); //this will throw an exception } catch(ArrayIndexOutOfBoundsException ex) { System.out.println("ArrayIndexOutOfBoundsException raised."); } } } |
Output: Happy Learning :). Please leave Read more