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Category Archives: Core Java

Performance Issue with HashSet RemoveAll() method

October 12, 2017
Posted by Pumpkin

In our previous article on HashSet internals, we have seen internal implementation of its add(), remove(), contains(), clear(), iterator() and isEmpty() methods. One of our readers has raised question about How efficient is HashSet removeAll() method? As it requires detailed explanation, we have decided to write separate article on it.   What does removeAll() method do? Before going into internals of […]

How is HashSet implemented internally in Java?

September 27, 2017
Posted by Pumpkin

In our previous article, we have seen internal implementation of SynchronizedMap and the difference between HashMap, Hashtable, SynchronizedMap and ConcurrentMap.  In this article, we will understand how does HashSet work internally? How JDK implementers have reused HashMap effectively for HashSet implementation.   The best way to understand internal implementation of any built-in Java class is by looking into its […]

Hashtable vs SynchronizedMap vs ConcurrentHashMap

Java Collection classes are heart of Java API.  It is essential to use built-in java collections like HashMap, ArrayList or LinkedList for accessing, storing and processing data in java applications. For Example, we have extensively used HashMap to transfer data between two layers of our MVC framework.   In all core java interviews, you will definitely face questions on […]

String Pool | Java

September 2, 2017
Posted by Pumpkin

String pool in Java is a pool of String literals and interned Strings in JVM for efficient use of String object. Since String is Immutable Class In Java, it makes sense to cache and shares them in JVM. Java creators introduced this String pool construct as an optimization on the way String objects are allocated […]

Access Modifiers in Java

September 2, 2017
Posted by Pumpkin

In this article, we will discuss one of the basic feature of Java- Access Modifiers. As the name suggests access modifiers in Java helps to restrict the scope of a class, constructor, variable, method or data member. Assigning an access modifier to a class, constructor, field or method is also sometimes referred to as "marking" that […]

Types of Class Loader | Delegation Algorithm | JVM Internals

August 13, 2017
Posted by Pumpkin

In previous articles, we learned about JVM architecture and one of its component Class Loader SubSystem. In this article,  we will discuss about Types of Class Loaders and How Class Loader uses Parent delegation Algorithm to load the class. If you have not gone through previous article on JVM Internals, I would encourage you to read that first. […]

Class Loader SubSystem | JVM Internals

August 5, 2017
Posted by Pumpkin

​In our previous article of JVM internals series, we learned about what is JVM, basic architecture of JVM and briefly understood its components. In this article we will discuss in detail about Class Loader SubSystem component of JVM architecture . Class Loader SubSystem Java’s dynamic class loading functionality is handled by the Class Loader SubSystem. […]

java.util.stream – Stream APIs basics | Java8

July 29, 2017
Posted by Pumpkin

In this article we will walk through basic overview of java.util.stream package. Package java.util.stream contains classes that support functional type of operations on streams of elements, such as map-reduce transformation, filtering etc. By the end of the article we will be able to answer following questions: 1. What is streams?  2. How it can be created?  […]

JVM Architecture Introduction | JVM Internals

July 26, 2017
Posted by Pumpkin

Being a java developer, it is expected from us to have basic knowledge of JVM architecture, as it enables us to write code more efficiently. Also from the interview perspective JVM architecture, Class loader subsystem, JVM memory management are frequently discussed topics with 3-5 year experienced java developer. If you are able to answer these questions, you will create good impression […]

What is the use of private constructor in java?

In Java, we can use any access modifier (i.e. public, protected or private) with constructor.  So, what are the uses of making constructor private? First thing that strikes your mind is Singleton Design Pattern which is also one of the most asked Core Java Interview Question to the 3-4 yr exp Java developers.  Apart from creating singleton class, private constructor […]

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