Constructor in Java


Constructors are special type of methods that are invoked at the time of creating the objects. If you use new keyword for creating the object, the constructors are called. There are certain restrictions imposed on these special type of methods. Constructors should have the same name as class name Constructors should not have any return […]

Method Overloading Vs Overriding in Java


In our previous tutorials we have explained about the method overloading and method overriding in Java. Read those tutorials for the more explanations. This tutorial highlights the only differences and when we have to use both the concepts. Both the concepts are based on the polymorphism in Java. Look at the below table for the […]

Method Overloading in Java


Method Overloading is the concept of writing multiple methods with the same name. Here the common characteristic is only the name. Parameters must be different. Return type can be anything. Also note that method overloading is within same class or inherited class. Look at the below points on how to overload a method. All the […]

Method Overriding in Java


Method Overriding is concept of overriding a same method in the child class. This is fall under the dynamic polymorphism  or run time polymorphism. A method defined in the parent class is considered as the common behaviour and the child classes are expected to override the common behaviour with own implementation. There are multiple restrictions enforced […]

Instanceof Operator


Instanceof Operator is important for writing the condition to check if a particular variable reference is of specific type / class. In short it is type checking condition. This operator returns true or false depends on the condition output. It always return false if you compare null value with any class. Lets look at an […]

Instance Initializer in Java


Instance initializer in Java is used for initializing the instance variables inside a class. It is a simple block without any modifiers used inside any class. If you declare a instance variable with value, then this value can be overridden in the instance initializer or in the constructor. The order of the execution as follows: […]

Access Modifiers in Java


This tutorials explains the various access modifiers used in Java language and the scope for the each modifier. There is four types of access modifiers in Java. private default protected public Private Modifier If you declare anything private inside a class, then it must be accessed inside that class. Other classes can not access that […]

OCPJP 6 Mock Exam -10


1 . Given: What is the result? Compilation succeeds Compilation fails because of an error on line 1 Compilation fails because of an error on line 3 Compilation fails because of an error on line 7 2 . Given: The ClassA class can be compiled successfully by inserting one of three possible options on line 3. […]

Java Keywords


Java has more than 50 keywords for the different operations. Here is the list of all the keywords and its purpose. Keyword Description abstract Abstract keyword can be use with classes and methods to defer the actual implementation to the child classes. assert This keyword used for testing the truth of a condition. boolean Indicates […]

Static Keyword


Static keyword in Java used for indicating the members are belong to the class and not to the instance. It means that, if you declare a static members, it is shared among all the instances of that class. Also note that the static members are initialized before the instance creation of that class. Static keyword […]