Java Questions

An abstract class can have instance methods that implement a default behavior. An Interface can only declare constants and instance methods, but cannot implement default behavior and all methods are implicitly abstract. An interface has all public members and no implementation. An abstract class is a class which may have the usual flavors of class members (private, protected, etc.), but has some abstract methods.

These are accessibility modifiers. Private is the most restrictive, while public is the least restrictive. There is no real difference between protected and the default type (also known as package protected) within the context of the same package, however the protected keyword allows visibility to a derived class in a different package.

The JDBC Driver provides vendor-specific implementations of the abstract classes provided by the JDBC API. This driver is used to connect to the database.

Overriding is a method with the same name and arguments as in a parent, whereas overloading is the same method name but different arguments

Non-static member class is a class defined inside outer class with out static modifier.

EX:

class A { // top level class or outer class

    ......

    class B { //non-static member class

    }

    .....

}

The JVM performs three main tasks:

• Loads code

• Verifies code

• Executes code

ClassName refName = new ClassName();

or

ClassName refName;

refName = new ClassName();

Package is a collection of related classes and interfaces. package declaration should be first statement in a java class.