Hey there! Welcome to ClearUrDoubt.com. In this post, we will look at removing nulls from an ArrayList in Java 8. Using Stream API, which was introduced in Java 8, we can remove null values from an ArrayList in a simple way. Read more
Hey there! Welcome to ClearUrDoubt.com. In this post, we will look at a program to remove duplicates from a List. Removing duplicate primitive and String values from List is a bit easy. We can use “Set” collection to remove the duplicates(if 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
Hey there! Welcome to ClearUrDoubt.com. In this post, we will look at the demo of List and ArrayList using forEach and Comparator in Java 8. forEach: brand new for loop for looping through the objects in a collection using lambda expressions Comparator: Java 8 Read more