Hey there! Welcome to ClearUrDoubt.com. In this post, we will look at a Core Java program to sort the elements of an array. We will use the Insertion Sort technique to sort the array elements. Insertion Sort is good for small datasets. Read more
Hey there! Welcome to ClearUrDoubt.com. In this post, we will look at a Core Java program to reverse an array of elements. Let’s take an integer array and try to reverse it.
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package com.clearurdoubt; import java.util.Arrays; public class ReverseArray { public static void main(String[] args) { int[] ints = new int[] {1,2,3,4,5,6,7,8,9,10}; System.out.println("Before reversing the Array: "); System.out.println(Arrays.toString(ints)); ints = reverse(ints); System.out.println(); System.out.println("After reversing the Array: "); System.out.println(Arrays.toString(ints)); } /** * Method to reverse the elements of an array * @param input is an array of integers * @return the reversed array. */ public static int[] reverse(int[] input) { int forwardIndex = 0, backwardIndex = input.length - 1; while(forwardIndex < backwardIndex) { int temp = input[forwardIndex]; input[forwardIndex++] = input[backwardIndex]; // increment the forwardIndex input[backwardIndex--] = temp; // decrement the backwardIndex } return input; } } |
Output: Happy Learning :). Please leave a reply Read more
Hey there! Welcome to ClearUrDoubt.com. In this post, we will look at a Core Java program to remove duplicates from an array of Strings. Here is the program:
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package com.clearurdoubt; import java.util.Arrays; public class RemoveDups { public static void main(String[] args) { String[] dups = new String[] {"ONE", "TWO", "THREE", "TWO", "ONE",}; String[] nodups = new String[dups.length]; System.out.println("Before removing duplicates: "); System.out.println(Arrays.toString(dups)); // Loop through the elements of dups array for(int i=0, j=0; i < dups.length; i++) { boolean isDuplicate = false; // Check if the current element in dups exists in nodups array. for(int k=0; k < nodups.length; k++) { if(nodups[k] == null) break; if(nodups[k].equals(dups[i])) { isDuplicate = true; break; } } // If the current element is not a duplicate, add to nodups array if(!isDuplicate) { nodups[j++] = dups[i]; } } // Let's find the true size of the nodups array int size = 0; // Remove nulls so that nodups array contains only the non-null elements for(int i = 0; i < nodups.length; i++) { if( nodups[i] == null) { size = i; break; } } // Create a new array with the "size" elements and copy the values so that nulls will be truncated nodups = Arrays.copyOf(nodups, size); System.out.println(); System.out.println("After removing duplicates: "); System.out.println(Arrays.toString(nodups)); } } |
Output: Happy Learning :). Please leave a reply in case of any Read more
Hey there! Welcome to ClearUrDoubt.com. In this post, we will look at a Java Program to handle exceptions while reading user input from the console. Exceptions are unexpected events that occur during the execution of a program. An exception might 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 a Spark(2.3.0) Program to load a CSV file into a Dataset using Java 8. Please go through the below post before going through this post. Program to load a Read more
Hey there! Welcome to ClearUrDoubt.com. In this post, we will look at a program to load a text file into a Dataset in Spark(2.3.0) using Java 8. Check out the below classes/concepts before going through the program: static org.apache.spark.sql.functions.col org.apache.spark.sql.Dataset org.apache.spark.sql.Row Read more
Hey there! Welcome to ClearUrDoubt.com. In this post, we will look at the WordCount program in Spark using Java 8. Before going through the below program, it’s better to look into below concepts for a better understanding of the program: org.apache.spark.api.java.JavaRDD org.apache.spark.api.java.JavaPairRDD 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