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Listing 4 . The class named MyClass.
class MyClass{ int data;MyClass(){ data = 0;}//end noarg constructor MyClass(int data){this.data = data; }//end parameterized constructorpublic String toString(){ return "" + data;}//end overridden toString() }//end MyClass

The class named TheComparator

That brings us to the class named TheComparator from which the Comparator object was instantiated and passed to the constructor for the TreeSet object in Listing 2 . The declaration for the class named TheComparator is shown in Listing 5 .

Listing 5 . Beginning of the class named TheComparator.
class TheComparator implements Comparator,Serializable{

As you can see, the class named TheComparator implements both the Comparator interface and the Serializable interface.

Implementing the Comparator interface

By implementing the Comparator interface, an object instantiated from the class is eligible to be passed to the constructor for a TreeSet object, which requires an incoming parameter of type Comparator .

Implementing the Serializable interface

Here is what Oracle has to say about implementing the Serializable interface:

"Note: It is generally a good idea for comparators to implement java.io.Serializable, as they may be used as ordering methods inserializable data structures (like TreeSet, TreeMap). In order for the data structure to serialize successfully, the comparator (if provided) mustimplement Serializable."

Since the Serializable interface doesn't declare any methods, implementing the interface simply requires a declaration that the interface isbeing implemented.

Methods of the Comparator interface

The Comparator interface declares the two methods listed below:

  • public int compare (Object o1, Object o2)
  • public boolean equals (Object obj)

As is always the case when implementing interfaces, a class that implements the Comparator interface must provide concrete definitions for both of these methods.

The compare method

The beginning of the compare method is shown in Listing 6 .

Listing 6 . Beginning of the compare method.
public int compare(Object o1,Object o2){ if(!(o1 instanceof MyClass))throw new ClassCastException(); if(!(o2 instanceof MyClass))throw new ClassCastException();

The purpose of a Comparator is to compare the values stored in the instance variables of two objects and to return a value indicating which objectis greater .

Specialization is required

Generally speaking, therefore, a Comparator object must be specialized to deal with a particular type of object. That type could be

  • A specific class from which the object is instantiated,
  • A specific interface implemented by the class from which the object is instantiated, or perhaps
  • A specific superclass of the class from which the object is instantiated.

The code in Listing 6 confirms that both of the objects to be compared are of the correct type, which in this case is type MyClass .

Must gain access to instance variables

Regardless of how the type is established, the code in the compare method of the Comparator object must gain access to the instance variables of the two objects passed to the compare method as type Object . This normally requires that a downcast be performed on the incoming object references.

Questions & Answers

how can chip be made from sand
Eke Reply
is this allso about nanoscale material
Almas
are nano particles real
Missy Reply
yeah
Joseph
Hello, if I study Physics teacher in bachelor, can I study Nanotechnology in master?
Lale Reply
no can't
Lohitha
where is the latest information on a no technology how can I find it
William
currently
William
where we get a research paper on Nano chemistry....?
Maira Reply
nanopartical of organic/inorganic / physical chemistry , pdf / thesis / review
Ali
what are the products of Nano chemistry?
Maira Reply
There are lots of products of nano chemistry... Like nano coatings.....carbon fiber.. And lots of others..
learn
Even nanotechnology is pretty much all about chemistry... Its the chemistry on quantum or atomic level
learn
Google
da
no nanotechnology is also a part of physics and maths it requires angle formulas and some pressure regarding concepts
Bhagvanji
hey
Giriraj
Preparation and Applications of Nanomaterial for Drug Delivery
Hafiz Reply
revolt
da
Application of nanotechnology in medicine
has a lot of application modern world
Kamaluddeen
yes
narayan
what is variations in raman spectra for nanomaterials
Jyoti Reply
ya I also want to know the raman spectra
Bhagvanji
I only see partial conversation and what's the question here!
Crow Reply
what about nanotechnology for water purification
RAW Reply
please someone correct me if I'm wrong but I think one can use nanoparticles, specially silver nanoparticles for water treatment.
Damian
yes that's correct
Professor
I think
Professor
Nasa has use it in the 60's, copper as water purification in the moon travel.
Alexandre
nanocopper obvius
Alexandre
what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
Rafiq
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
Damian
How we are making nano material?
LITNING Reply
what is a peer
LITNING Reply
What is meant by 'nano scale'?
LITNING Reply
What is STMs full form?
LITNING
scanning tunneling microscope
Sahil
how nano science is used for hydrophobicity
Santosh
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
Rafiq
what is differents between GO and RGO?
Mahi
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
Rafiq
if virus is killing to make ARTIFICIAL DNA OF GRAPHENE FOR KILLED THE VIRUS .THIS IS OUR ASSUMPTION
Anam
analytical skills graphene is prepared to kill any type viruses .
Anam
Any one who tell me about Preparation and application of Nanomaterial for drug Delivery
Hafiz
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
Bob
The nanotechnology is as new science, to scale nanometric
brayan
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Damian
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Source:  OpenStax, Object-oriented programming (oop) with java. OpenStax CNX. Jun 29, 2016 Download for free at https://legacy.cnx.org/content/col11441/1.201
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