The EXISTS condition in SQL is used to check whether the result of a correlated nested query is empty (contains no tuples) or not. The result of EXISTS is a boolean value True or False. It can be used in a SELECT, UPDATE, INSERT or DELETE statement. Syntax: SELECT column_name(s) FROM table_name WHERE EXISTS (SELECT… Read More »

Java.lang.Compiler Class in Java

Compiler Class provides support and related services to Java code to Native Code. Native code is a form of code that can be said to run in a virtual machine (for example, [JVM]Java Virtual Machine). Declaration : public final class Compiler extends Object Methods : command() : java.lang.Compiler.command() tests the argument type and performs some… Read More »

Java.lang.Void Class in Java

Java.lang.Void class is a placeholder which holds a reference to a class object if it represents void keyword. It is a uninstantiable placeholder. Well, uninstantiable means that this class have a private constructor and no other constructor that we can access from outside. Methods of lang.void class are all inherited from Object class in Java:… Read More »

Java.lang.Character.UnicodeBlock Class in Java

Character.UnicodeBlock Class represents particular Character blocks of the Unicode(standards using hexadecimal values to express characters – 16 bit) specifications. Character Blocks define characters used for specific purpose. Declaration : public static final class Character.UnicodeBlock extends Character.Subset Methods of Character.UnicodeBlock Class : forName() : java.lang.Character.UnicodeBlock.forName() returns the name of Unicode Blocks, which are determined by the… Read More »

Top 20 Greedy Algorithms Interview Questions

Greedy is an algorithmic paradigm that builds up a solution piece by piece, always choosing the next piece that offers the most obvious and immediate benefit. Greedy algorithms are used for optimization problems. ‘Recent Articles’ on Greedy Algorithms ‘Coding Problems’ on Greedy Algorithms ‘Quiz’ on Greedy Algorithms ‘Videos’ on Greedy Algorithms   Activity Selection Problem… Read More »

Path Traversal Attack and Prevention

A path traversal attack allows attackers to access directories that they should not be accessing, like config files or any other files/directories that may contains server’s data not intended for public. Using a path traversal attack (also known as directory traversal), an attacker can access data stored outside the web root folder (typically /var/www/). By… Read More »

Circular Queue | Set 2 (Circular Linked List Implementation)

Prerequisite – Circular Singly Linked List We have discussed basics and how to implement circular queue using array in set 1. Circular Queue | Set 1 (Introduction and Array Implementation) In this post another method of circular queue implementation is discussed, using Circular Singly Linked List. Operations on Circular Queue: Front:Get the front item from… Read More »