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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

Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
Renato
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
?
Kyle
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
Adin
why?
Adin
what school?
Kyle
biomolecules are e building blocks of every organics and inorganic materials.
Joe
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
research.net
kanaga
sciencedirect big data base
Ernesto
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
Bharti
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
Daniel
how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
Maciej
characteristics of micro business
Abigail
for teaching engĺish at school how nano technology help us
Anassong
Do somebody tell me a best nano engineering book for beginners?
s. Reply
there is no specific books for beginners but there is book called principle of nanotechnology
NANO
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
s.
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
Tarell
what is the actual application of fullerenes nowadays?
Damian
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
Tarell
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
Virgil
is Bucky paper clear?
CYNTHIA
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
NANO
so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Harper
Do you know which machine is used to that process?
s.
how to fabricate graphene ink ?
SUYASH Reply
for screen printed electrodes ?
SUYASH
What is lattice structure?
s. Reply
of graphene you mean?
Ebrahim
or in general
Ebrahim
in general
s.
Graphene has a hexagonal structure
tahir
On having this app for quite a bit time, Haven't realised there's a chat room in it.
Cied
what is biological synthesis of nanoparticles
Sanket Reply
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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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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