Explain the equals() method, JAVA Programming

Assignment Help:

Explain the equals() method

The equals() method of java.lang.Object acts the similar as the == operator; that is, it tests for object identity rather than object equality. The implicit contract of the equals() method, thus, is that it tests for equality rather than identity. Therefore most classes will override equals() along with a version that does field through field comparisons before deciding while to return true or false.

To elaborate, an object created through a clone() method (that is a copy of the object) should pass the equals() test if neither the original nor the clone has changed because the clone was created. Therefore the clone will fail to be == to the original object.

For instance, here is an equals() method you could use for the Car class. Two cars are equal if and only if their license plates are equal, and that's what this techniques tests for.
public boolean equals(Object o) {

if (o instanceof Car) {
Car c = (Car) o;
if (this.licensePlate.equals(c.licensePlate)) return true;
}
return false;
}
This example is particularly interesting since it demonstrates the impossibility of writing a useful generic equals() method in which tests equality for any object. It is not sufficient to easily test for equality of all the fields of two objects. It is whole possible that some of the fields might not be relevant to the test for equality as in this instance where changing the speed of a car does not change the in fact car that's referred to.

Be careful to prevent this common mistake when writing equals() methods:
public boolean equals(Car c) {

if (o instanceof Car) {
Car c = (Car) o;
if (this.licensePlate.equals(c.licensePlate)) return true;
}
return false;

}
The equals() method must permit tests against any object of any class, not simply against other objects of the similar class (Car in this example.)

You do not requires to test whether o is null. null is never an instance of any class. null instanceof Object returns false.


Related Discussions:- Explain the equals() method

the file system simulator , • Study and enhance the File System Simulator ...

• Study and enhance the File System Simulator - See the FS_sim slide deck • New features - blockinfo - a new application that displays the information about the blocks in the file

I want customize tumblr theme, I need Customize Tumblr theme Project Des...

I need Customize Tumblr theme Project Description: I have a blog here I would like to customize it as follows; 1) Modify the horizontal navigation from the bottom of th

Overloaded Methods, QUESTION 3: Overloaded methods Write the overloaded me...

QUESTION 3: Overloaded methods Write the overloaded method named average () for each of the following problems: a) The first method receives THREE (3) integer values and returns

Explain the java.net package, Explain The java.net package Each package...

Explain The java.net package Each package describes a number of classes, interfaces, exceptions, and errors. For instance, the java.net package contains these, classes, interfa

Luminous Jewels, Byteland county is very famous for luminous jewels. Lumino...

Byteland county is very famous for luminous jewels. Luminous jewels are used in making beautiful necklaces. A necklace consists of various luminous jewels of particular colour. Nec

Decode the code, By pressing ‘6’ (i.e. key’6’ one time) on the keypad, the ...

By pressing ‘6’ (i.e. key’6’ one time) on the keypad, the mobile shows ‘m’ on display screen in write text message area

Write a program that will analyze stocks, Write a program in java that will...

Write a program in java that will analyze stock data and purchase stock with the user''s specific risk and investment. User will select risk from a GUI, high, medium or low and inp

Android Development Project, Task I have an Android mobile app project tha...

Task I have an Android mobile app project that I''m trying to get profiles to transfer by connecting to a server at 23.23.175.213 port 1337. I have to send a json string to the se

Write names of the dos attacks phases, Write names of the DoS attack's phas...

Write names of the DoS attack's phases? DoS (Denail of service): DoS attach has in total 3 kinds of phases and below they are listed: 1. Search 2. Arm 3. Attack

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd