Add to Favorites    Make Home Page 21404 Online  
 Language Categories  
 Our Services  

Java Data Structures - Contents


Comparing Objects...

A D V E R T I S E M E N T

Search Projects & Source Codes:

    Comparing Objects in Java can be a daunting task, especially if you have no idea how it's done. In Java, we can only compare variables of native type. These include all but the objects (ex: int, float, double, etc.). To compare Objects, we have to make objects with certain properties; properties that will allow us to compare.

    We usually create an interface, and implement it inside the objects we'd like to compare. In our case, we'll call the interface pComparable. Interfaces are easy to write, since they're kind of like abstract classes.

public interface pComparable{
    public int compareTo(Object o);
}

    As you can see, there is nothing special to simple interfaces. Now, the trick is to implement it. You might be saying, why am I covering comparing of objects right in the middle of a binary tree discussion... well, we can't have a binary search tree without being able to compare objects. For example, if we'd like to use integers in our binary search tree, we'll have to design our own integer, and let it have a pComparable interface.

    Next follows our implementation of pInteger, a number with a pComparable interface. I couldn't just extend the java.lang.Integer, since it's final (cannot be extended) (those geniuses!).

public class pInteger implements pComparable{
    int i;

    public pInteger(){
    }
    public pInteger(int j){
        set(j);
    }
    public int get(){
        return i;
    }
    public void set(int j){
        i = j;
    }
    public String toString(){
        return ""+get();
    }
    public int compareTo(Object o){
        if(o instanceof pInteger)
            if(get() > ((pInteger)o).get())
                return 1;
            else if(get() < ((pInteger)o).get())
                return -1;
        return 0;
    }
}

    I believe most of the interface is self explanatory, except maybe for the compareTo(Object) method. In the method, we first make sure that the parameter is of type pInteger, and later using casting, and calling methods, we compare the underlying native members of pInteger and return an appropriate result.

    A note on JDK 1.2: In the new versions of the JDK, you won't need to implement your own pComparable, or your own pInteger; since it's built in! There is a Comparable interface, and it's already implemented by the built in java.lang.Integer, java.lang.String, and other classes where you might need comparisons. I'm doing it this way only for compatibility with the older versions of JDK. I'll talk about JDK 1.2 features later in this document (hopefully).


Back to Table of Contents


A D V E R T I S E M E N T




Google Groups Subscribe to SourceCodesWorld - Techies Talk
Email:

Free eBook - Interview Questions: Get over 1,000 Interview Questions in an eBook for free when you join JobsAssist. Just click on the button below to join JobsAssist and you will immediately receive the Free eBook with thousands of Interview Questions in an ebook when you join.

 Advertisements  

Google Search

Google

Source Codes World.com is a part of Vyom Network.

Vyom Network : Web Hosting | Dedicated Server | Free SMS, GRE, GMAT, MBA | Online Exams | Freshers Jobs | Software Downloads | Interview Questions | Jobs, Discussions | Placement Papers | Free eBooks | Free eBooks | Free Business Info | Interview Questions | Free Tutorials | Arabic, French, German | IAS Preparation | Jokes, Songs, Fun | Free Classifieds | Free Recipes | Free Downloads | Bangalore Info | Tech Solutions | Project Outsourcing, Web Hosting | GATE Preparation | MBA Preparation | SAP Info | Software Testing | Google Logo Maker | Freshers Jobs

Sitemap | Privacy Policy | Terms and Conditions
Copyright ©2003-2018 SourceCodesWorld.com, All Rights Reserved.
Page URL: http://www.sourcecodesworld.com/articles/java/java-data-structures/Comparing_Objects.asp


Download Yahoo Messenger | Placement Papers | Free SMS | C Interview Questions | C++ Interview Questions | Quick2Host Review