Techie Shah

Introduction In this post, we will learn to convert String to int primitive data type. Java provides the Integer wrapper class to convert a String to int. Integer.parseInt(String) String numberString = "134"; int number = Integer.parseInt(numberString ); System.out.println(number); Output : 134 Integer.valueOf(String) String numberString = "134"; int number = Integer.valueOf(numberString ); System.out.println(number); Output : 134 The following code will throw NumberFormatException //134a cannot be converted to Integer String numberString = "134a"; int number = Integer.valueOf(numberString ); System.out.println(number); Exception in thread "main" java.lang.NumberFormatException: For input string: "134a" at java.lang.NumberFormatException.forInputString(Unknown Source) at java.lang.Integer.parseInt(Unknown Source) at java.lang.Integer.valueOf(Unknown Source) at StringExample.main(StringExample

Introduction String is the most widely used class in any language. In this post, we will explore String in Java context. This post will help you to understand the String in-depth and to answer String related questions in a Job interview. 1. What is String? String is a final class in Java and not a primitive data type like int, float, etc. It is defined in java.lang package and therefore available by default. 2. How to create objects of String? There are two ways to create String a. String literals String str = "abc"; b. Using new operator String str = new String("abc"); 3. Where is String stored in memory? String literals are stored in the String constant pool. A string is called immutable or constant i.e. once created then it can not be changed. Whenever we create a String using double quotes (String literal), Java looks into the String constant pool if an object with the same value is present, it returns the reference to that object

Introduction In this post, we will use prime numbers to compare anagrams. We will assign the prime number to each character in a string and then multiply them. Two strings will be equal if their product is the same. Implementation in Java public class PrimeAnagram { static int [] alphaPrime = {5,7,11,13,17,19,23,29,31,37,41,43,47,53,59,61,67,71,73,79,83,89,97,101,103,107}; static String alphabets = "abcdefghijklmnopqrstuvwxyz"; public static void main(String[] args) { System.out.println(isPrimeAnagram("parse", "spare")); } private static boolean isPrimeAnagram(String value1,String value2) { return getPrime(value1) == getPrime(value2); } private static int getPrime(String value) { value = value.toLowerCase(); int productValue = 1; for(int index = 0; index < value.length(); index++) { productValue *= alphaPrime[ alphabets.indexOf(value.charAt(index)) ]; } return productValue; } } Conclusion We

Introduction I have been often asked this question in an interview to write a code of Singleton pattern. I have noticed that developers have the knowledge of what is Singleton pattern but often they forget the key points regarding its implementation. In this post, I will highlight the key points to remember for your upcoming interview. Implementation public class Singleton { private static Singleton instance; private Singleton() { } public static synchronized Singleton getInstance() { if(instance == null) { instance = new Singleton(); } return instance; } } Key Points to remember a) instance is declared as private and static  b) The constructor is declared as private c) getInstance method is static and synchronized to make it thread free Conclusion In this post, we learned how to implement the Singleton pattern using Java language. We have also noted down the key points to remember.Please leave your comments in the comments box.

Introduction FizzBuzz is one of the popular coding puzzles asked in a programming interview. In this post, we will learn its implementation using Java 8. Problem We have 1 to n Integers. Write a program that iterates over these integers, print Fizz if Integer is multiple of 3, print Buzz if Integer is multiple of 5, print FizzBuzz if Integer is multiple of both 3 and 5 else print the Integer.  Solution import java.util.stream.IntStream; public class FizzBuzz { public static void main(String[] args) { int n = 100; IntStream.range(1, n).forEach( i -> { /* if( i % 3 == 0 && i % 5 == 0 ) is equivalent to i % 15 == 0 * and will reduce lines of code */ if( i % 15 == 0) { System.out.println("FizzBuzz"); }else if ( i % 3 == 0) { System.out.println("Fizz"); }else if ( i % 5 == 0) { System.out.println("Buzz"); }else { System.out.println(i); } }); } } Note that multiple of 15 is mult

Introduction In this post, we will explore different ways to sort Java collections in a certain order. Java platform provides a  Collections framework that represents a group of objects. All the Java classes those implement the Collection interface have by default implemented the sort method i.e. Collections.sort(list/set/Array) Java classes like String, Date, Integer, Double, Float, Long, Integer etc implements the Comparable interface by default. Java provides us with the following two interfaces to compare and sort the custom objects Comparable Interface  public interface Comparable<T> { public int compareTo(T o); } Java 8 also provides the built in Comparator.comparing method that returns an instance of Comparable. Comparator Interface public interface Comparator<T> { int compare(T o1, T o2); } In this post we will use the following student class for practice. public class Student{ public String name; public Integer age; public St

Introduction In this post, we will learn the following two examples a) Sort single String in alphabetical order b) Sort array of Strings Sort single String in alphabetical order import java.util.Arrays; public class SortStringAlphabetical { private static String inputString = "The quick brown fox jumps over the lazy dog"; public static void main(String[] args) { System.out.println("Input String : " + inputString); char [] characters = inputString.toCharArray(); Arrays.sort(characters); System.out.println("Alphabetical sorted String : " + new String(characters)); } } Output Input String : The quick brown fox jumps over the lazy dog Alphabetical sorted String :         Tabcdeeefghhijklmnoooopqrrstuuvwxyz Sort array of Strings import java.util.Arrays; public class SortStringArrayAlphabetical { private static String inputStrings[] = {"efg","xyz","abc"}; public static void ma

Problem Recently we migrated Hibernate to the latest version i.e. 5.4.4. Multiple depreciation warnings appeared in our code i.e. The type Query<R> is deprecated The method setString(String, String) from the type Query is deprecated The method uniqueResult() from the type Query is deprecated The method setBoolean(String, boolean) from the type Query is deprecated The method setLong(String, long) from the type Query is deprecated Solution Existing Change To import org.hibernate.Query; import org.hibernate. query .Query; query . setLong ( "serviceId" , serviceId ) ; query . setParameter ( "serviceId" , serviceId ); query . setBoolean ( "isDelete" ,Boolean. FALSE ) ; query . setParameter ( "isDelete" ,Boolean. FALSE ) ; query . setString ( "serviceNo" , serviceNo ) ; query . setParameter ( "serviceNo"

Introduction Selection sort is the simplest sorting algorithm in terms of implementation. Let's consider we have a list of elements i.e. {3, 9, 0, 5, 4 } a) Selection sort maintains two sublists, one sorted and initially empty and second unsorted sublist i.e. [ {}, {3, 9 , 0, 5 ,4 }] b) It searches for the minimum element (for ascending sort) OR for a maximum element( for descending sort) in the unsorted list in each step. Step 1 [ {0 }, {9,3,5,4}] Minimum element = 0 , swapped with 3 Step 2 Minimum element = 3 , swapped with 9 [{0,3) , {9,5,4} ] Step 3 Minimum element = 4 , swapped with 9 [{0,3,4} , {5,9}] Step 4 Minimum element = 5 , swapped with itself [{0,3,4,5}, {9}] Step 5 Minimum element = 9 , swapped with itself [{0,3,4,5,9}, {}] Worst Complexity: O(n*n) Best Complexity   : O(n * n) Implementation package main.scala object SelectionSort { val array = Array(0, 5, 2, 6, 3, 1) def main(args: Array[String]) { print(&quo

Introduction Selection sort is the simplest sorting algorithm in terms of implementation. Let's consider we have a list of elements i.e. {3, 9, 0, 5, 4 } a) Selection sort maintains two sublists, one sorted and initially empty and second unsorted sublist i.e. [ {}, {3, 9 , 0, 5 ,4 }] b) It searches for the minimum element (for ascending sort) OR for a maximum element( for descending sort) in the unsorted list in each step. Step 1 [ {0 }, {9,3,5,4}] Minimum element = 0 , swapped with 3 Step 2 Minimum element = 3 , swapped with 9 [{0,3) , {9,5,4} ] Step 3 Minimum element = 4 , swapped with 9 [{0,3,4} , {5,9}] Step 4 Minimum element = 5 , swapped with itself [{0,3,4,5}, {9}] Step 5 Minimum element = 9 , swapped with itself [{0,3,4,5,9}, {}] Worst Complexity: O(n*n) Best Complexity   : O(n * n) Imperative style implementation using Java 7 public class SelectionSortExample { private static int array[] = {3,9,0,5,4}; public static void mai