Java Questions

Various elements of OOP are:

• Object

• Class

• Method

• Encapsulation

• Information Hiding

• Inheritance

• Polymorphism

yes if the method is ovreriding method

no if the method is not overriding method

Pass By Reference means the passing the address itself rather than passing the value. Passby Value means passing a copy of the value to be passed.

Use Interfaces when…

- You see that something in your design will change frequently.

- If various implementations only share method signatures then it is better to use Interfaces.

- You need some classes to use some methods which you don't want to be included in the class, then you go for the interface, which makes it easy to just implement and make use of the methods defined in the interface.

Use Abstract Class when…

- If various implementations are of the same kind and use common behavior or status then abstract class is better to use.

- When you want to provide a generalized form of abstraction and leave the implementation task with the inheriting subclass.

- Abstract classes are an excellent way to create planned inheritance hierarchies. They're also a good choice for nonleaf classes in class hierarchies.

Path and Classpath are operating system level environment variales. Path is used define where the system can find the executables(.exe) files and classpath is used to specify the location .class files.

Wrapped classes are classes that allow primitive types to be accessed as objects.

To use an iterator to traverse through the contents of a collection, follow these steps:

- Obtain an iterator to the start of the collection by calling the collections iterator() method.

- Set up a loop that makes a call to hasNext(). Have the loop iterate as long as hasNext() returns true.

- Within the loop, obtain each element by calling next().

Autoboxing is the process of converting a primitive type data into its corresponding wrapper class object instance.

Example:

Integer number = new Integer (100); // number is now refers to the object 100

Unboxing is the process of converting a wrapper instance into a primitive type.

Example: 

Integer number = new Integer (100); 

int num = number;// without type casting number would be changed into int type