Java/J2EE

Hashmap Internal Implementation Analysis in Java: Full detailed analysis of java.util.HashMap’s implementation and its internals and working concepts

Creating our own hashmap in java: This is an attempt to come up with my own hashmap in java. It serves all basic needs of original java.util.HashMap with O(1) complexity in read operations…

When to use ArrayList and LinkedList in java: These two data structures(DS) operate exactly opposite in terms of read and write operations…

how does polymorphism works within the constructors: First of all it is not good practice to call any instance methods inside the constructor, if we cannot avoid then do as little as possible. What happens…

How does DriverManager identify the type of driver loaded into JVM: who will instantiate the class that is loaded and who will register that class with DM? It is done through the static block of …

Different ways of getting a new object in Java: Using new operator; using Class.forName(“”); Using clone method; Deserialization…

Can we propagate exceptions in threads?: Prior to Java1.5 we cannot because the run() method in Runnable interface is written such that there is no…

Why would one need try-finally block combination: If we dont wanna handle the exception and instead propogate it up the hierarchy then we go for try-finally combination

The Internal Architecture of JVM: Java Virtual Machine components are depicted in below diagram. Each time we run java_application/java_class, an instance of JVM gets created…

Security aspects of standalone utilities in java: Security aspects of java application development: make sure the utility does not accept any file input that can be used in edit (write) mode, this way…

Immutable Objects and Strings in Java: Why are Strings made immutable? Security Reasons: as strings are used in class loaders, if it is made mutable it could lead to a potential security threat…

Serialization Mechanism: Serialization is a mechanism by which you can save the state of an object by converting it to a byte stream.The class whose instances are to be serialized should implement an interface Serializable…

Analysing Java Garbage Collector: Application Phases: Initialization → Steady state → Summary (optional); – Initialization: startup, lots of allocations…

Internals of Java Garbage Collector GC Responsibilities-Garbage Detection: Garbage are objects that are no longer reachable – Garbage Reclamation:Make space available to the running program again

Garbage collector tuning in JAVA HOTSPOT JVM: Garbage collector tuning in JAVA HOTSPOT JVM: GC Basics; Analysing GC; Memory Footprint; Latencies; Types of Collectors; Summary

password policy with regular expression: Password policy to match minimum 8 characters password with alphabets in combination with numbers or special characters

New Changes in JDK7: JDK7 is packaged with these new changes – Small language changes – NIO-2 Enhanced NIO – invokedynamic – other features

J2EE
Introduction to J2EE (2.x), its Architecture and Component Diagram: Java 2 Platform enterprise edition is an integrated set of individual APIs required for developing server side MULTI-TYRED, DISTRIBUTED, TRANSACTIONAL and SECURE applications…

Java Naming and Directory Interface (JNDI), JNDI Architecture: Naming Service? Is a service which allows us to store and retrieve simple objects with a unique name. It is just like one of the storage unit. Directory Service? Is an added service…

Java Security Model and its anatomy: Java Sandbox Model: Java has circumvented the virus or Trojan horse problems that plagued other models of software distributions. Java sandbox model is responsible for…

Introduction to Hibernate, Its Architecture: HIBERNATE is an ORM ( Object-Relational-Mapping) technology. It is an Open-Source and free technology , developed in SourceForge.net in JAVA. There have been a number of such ORM technologies,in recent past.. TopLink is one such tool…

Inversion of Control and Dependency Injection: Inversion of control is too broad term for the frameworks to claim that they are based on IoC. It depends on what control of the application are you inverting…

Acknowledgement modes in Java Message Server (JMS): There are two types – auto-acknowledge – dups-ok-acknowledge: auto-acknowledge: the acknowledge message from MDB to the JMS is sent as soon as the message is received. dups-ok-acknowledge…

Servlets and JSPs

where do the cookies get stored in the request object: Cookies are stored in the headers…

Is the exception implicit object available in all the JSP pages?: No, it is avaliable only in the error pages…

how do you navigate to error pages in JSP: In the page where exception might occur, add a page…

SQL

Transaction and ACID properties: A set of statements executed on a resource or resources applied with ACID properties is known as Transaction. Note: Here database is one resource but resource need not be only database. ACID Properties: …

What is the difference between sub query and co-related subquery: Sub Query: Here inner query gets executed first and based on the result of it the outer query is executed…

Implementation of relationships in sql: We have three types of relationships in SQL. one-to-one; one-to-many; many-to-many…

When should we use GROUP BY clause: When there is a need to aggregate/group values in a column based on some criteria in same/another column then we go for GROUP BY clause. Usage of Aggregate function on column: col_sales: …

frequent sql interview questions. Here some of the most common interview questions like where and having; distinct and group-by; union and union-all are …