Java Interview Questions and Answers - Part 6

What are the common tasks of JDBC? - Create an instance of a JDBC driver ....
Explain the concepts of Exceptions in Java - Exceptions are errors that occur at runtime and disrupt the normal flow of execution of instructions in a program...
What is class loader? Purpose of Bootstrap class loader - Class loader finds and loads the class at runtime. Java class loader can load classes from across network...
What is a TreeSet class? - TreeSet class is used to store large amount of data and uses tree for storage.....
String object is immutable, Explain. - This means once you have created String object and assigned a value, you can’t change the value of the object....
Difference between traditional java Array and Arraylist class - Traditional java array is fixed length whereas ArrayList supports dynamic arrays that can grow...
Difference between pass by value and pass by reference - In pass by value, a copy of variable is passed to the method; the values of the variable can’t be changed in the method.....
What are access modifiers in JAVA?
Define Savepoints in a transaction - Using Savepoint, you can mark one or more places in a transaction and you can perform rollback to one of those...
What are filter class in java? - The filter class in java can manipulate request before reaches to the web server. It can also manipulate response before it reaches the client browser......
How do we consume a web service in java? - Client can consume web services in java in 3 ways...
What is Reflection API in Java? - Reflection API allows examining, modifying the run time behaviour of java applications running in the JVM...
Difference between static and dynamic class loading - Static class loading: The process of loading a class using new operator is called static class loading...
What is LinkedList class? - LinkedList class implements the List interface. In addition to the List operations, the LinkedList class....
What is LinkedHashSet class? - LinkedHashSet combines the operations of LinkedList and HashSet, with the order of prediction for...
What is Map and SortedMap Interface? - A map is an object that maps the keys to values. Map provides the facility of storing elements without....
What is casting? What are the different types of Casting? - Type casting: Explicit conversion between incompatible types ( or ) changing entities from one data type.....
Advantages and disadvantages of interfaces - Interfaces are mainly used to provide polymorphic behavior, Interfaces function to break up the complex..
What is Multithreading? - A thread is one of the processes of an application. In multithreading, an OS allows different threads of an....
Describe the types of Beans - Stateless Session Beans, Statefull Session Beans, Entity Beans......
Explain the Common use of EJB - The EJBs can be used to incorporate business logic in a web-centric application......
What are transaction isolation levels in EJB? - Transaction_read_uncommitted, Transaction_read_committed, Transaction_repeatable_read......
What is Entity Bean? - The entity bean is used to represent data in the database. Entity beans provide a component model that allows.....
What is preinitialization of a servlet? - The process of loading a servlet before any request comes in is called preloading or preinitializing a servlet.....
What is the difference between JSP and Servlets? - JSP supports only HTTP protocol. But a servlet can support any protocol like HTTP, FTP, SMTP etc....
What is the difference between doGet() and doPost()? - GET Method: All data we are passing to Server will be displayed in URL. Here we have size limitation......
What's the difference between servlets and applets? - Unlike applets, servlets have no graphical user interface........
What is JSP? - JSP is a technology that returns dynamic content to the Web client using HTML, XML and JAVA elements....
A covariant return type allows to override a super class method that returns a type that sub class type of super class method’s return type. It is to minimize up casting and down casting......
A callable collection is an interface whose implementers define a single method with no arguments. The Callable interface resembles Runnable..
Java supports threads natively without using additional libraries. Using ‘synchronized’ key word makes the methods thread safe.......
The primary goal of a constructor is to create an object. Though the constructor resembles a method, its explicit purpose is to initialize the instance variables.....
The following are the steps to add a button in applet: 1. Declare and create the object of Button class - Button clickMe;....
A Jar file contains mostly .class files and optionally other files like sound files, image files for Java applications, gathered into a single file in the compressed format.....
The statement String s = “hello” is initialized to s and creates a single interned object....
The differences of Java and Java Script are: - Java can stand on its own where as Java Script mandatorily be placed within an HTML document.....
Upcasting: Java permits an object of a sub class can be referred by its super class. It is done automatically.....
Classpath is the path in which JVM searches for class libraries at the time of compiling the Java Application. By setting the CLASSPATH environment variable....
The OutOfMemoryException can occur either the JVM may have a limit of memory to access to, or the system may have run out of physical memory....
In a pooled database connection, it is returned to the pool and could close only after expiring its life time......