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naresh
Core Java Doubts
1 Answer(s)      4 years and 5 months ago
Posted in : Java Beginners


1)How to swap two numbers suppose a=5 b=10; without using third variable?
2)How to sort two strings? By using collections?
3)What is the difference between comparable and comparator?
4)When we go for Inheritance? And when we go for Interface?
5)What is difference between Abstraction and Encapsulation?
6)Give brief notes over collections? And their usage?

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June 5, 2010 at 4:03 PM


Hi Friend,

1)
class Swapping {
public static void main(String[] args) {
int num1 = 5;
int num2 = 10;
num1 = num1 + num2;
num2 = num1 - num2;
num1 = num1 - num2;
System.out.println("After swapping, num1= " + num1 + " and num2= "+ num2);
}
}

2)
import java.util.*;
class StringSort {
public static void main(String[] args){
String words[] = {"Rose","India"};
List list = Arrays.asList(words);
Collections.sort(list);
System.out.println(list);
}
}

3)
Differences:

a)A comparable object is capable of comparing itself with another object while a comparator object is capable of comparing two different objects.

b)The Comparable class itself implements the java.lang.Comparable interface in order to compare its instances while the Comparator class does not compare its instances, but some other class?s instances.

For more information, visit the following links:

http://www.roseindia.net/help/java/c/comparable-interface.shtml
http://www.roseindia.net/javacertification/scjp5/javacollections_generics.shtml

4)
For inheritance and interface, visit the following links:

http://www.roseindia.net/java/language/inheritance.shtml
http://www.roseindia.net/java/master-java/interface.shtml

5)Difference:

Abstraction - The process of abstraction in Java is used to hide certain details and only show the essential features of the object. In other words, it deals with the outside view of an object (interface).

Encapsulation - This is an important programming concept that assists in separating an object's state from its behavior. This helps in hiding an object's data describing its state from any further modification by external component. In Java there are four different terms used for hiding data constructs and these are public, private, protected and package. As we know an object can associated with data with predefined classes and in any application an object can know about the data it needs to know about. So any unnecessary data are not required by an object can be hidden by this process. It can also be termed as information hiding that prohibits outsiders in seeing the inside of an object in which abstraction is implemented.

6)
For Collections, visit the following link:

http://www.roseindia.net/javacodeexamples/index.shtml

Thanks


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