Using Java Constructors An Easy How-To Guide

A Java constructor creates a new instance of an already-defined object. This article discusses how to use Java constructor methods to create a Person object. Note: You need to create two files in the same folder for this example: Person.java defines the Person class, and PersonExample.java contains the main method that creates Person objects. The Constructor Method Lets start by creating a Person class that has four private fields: firstName, lastName, address, and username. These fields are private variables and together their values make up the state of an object. Weve also added the simplest of constructor methods: public class Person { private String firstName; private String lastName; private String address; private String username; //The constructor method public Person() { } } The constructor method is similar to any other public method except that it shares the same name as the class, and it cannot return a value. It can have none, one or many parameters. Currently, our constructor method does nothing at all, and its a good time to consider what this means for the initial state of the Person object. If we left things as they are or we didnt include a constructor method in our Person class (in Java you can define a class without one), then the fields would have no values — and we certainly want our person to have a name and address as well as other characteristics.  If you think theres a chance that your object might not be used as you expect and the fields might not be initialized when the object is created, always define them with a default value: public class Person { private String firstName ; private String lastName ; private String address ; private String username ; //The constructor method public Person() { } } Normally, to ensure that a constructor method is useful, we would design it to expect parameters. The values passed through these parameters can be used to set the values of the private fields: public class Person { private String firstName; private String lastName; private String address; private String username; // The constructor method public Person(String personFirstname, String personLastName, String personAddress, String personUsername) { firstName personFirstName; lastName personLastName; address personAddress; username personUsername; } // A method to display the state of the object to the screen public void displayPersonDetails() { System.out.println(Name: firstName lastName); System.out.println(Address: address); System.out.println(Username: username); } } Our constructor method now expects the values of four strings to be passed to it. They are then used to set the initial state of the object. Weve also added a new method called displayPersonDetails() to enable us to see the state of the object after it has been created. Calling the Constructor Method Unlike other methods of an object, the constructor method must be called using the new keyword: public class PersonExample { public static void main(String[] args) { Person dave new Person(Dave, Davidson, 12 Main St., DDavidson); dave.displayPersonDetails(); } } Heres what we did: To create the new instance of the Person object, we first define a variable of type Person that will hold the object. In this example, weve called it dave.On the other side of the equals sign, we call the constructor method of our Person class and pass it four string values. Our constructor method will take those four values and set the initial state of the Person object to be: firstName Dave, lastName Davidson, address 12 Main St, username DDavidson. Notice how weve switched to the Java main class to call the Person object. When you work with objects, programs will span multiple .java files. Make sure you save them in the same folder. To compile and run the program, simply compile and run the Java main class file (i.e., PersonExample.java). The Java compiler is smart enough to realize that you want to compile the Person.java file as well because it can see that you have used it in the PersonExample class. Naming of Parameters The Java compiler gets confused if the parameters of the constructor method have the same names as the private fields. In this example, you can see that we have distinguished between them by prefixing the parameters with the word person. Its worth mentioning that there is another way. We can use the this keyword instead: // The constructor method public Person(String firstName, String lastName, String address, String username) { this.firstName firstName; this.lastName lastName; this.address address; this.username username; } The this keyword tells the Java compiler that the variable to be assigned the value is the one defined by the class, not the parameter. Its a question of programming style, but this method helps us define constructor parameters without having to use multiple names. More Than One Constructor Method When designing your object classes, you are not limited to using only one constructor method. You might decide there are a couple of ways an object can be initialized. The only constraint on using more than one constructor method is that the parameters must differ. Imagine that at the time we create the Person object, we might not know the username. Lets add a new constructor method that sets the state of the Person object using only the firstName, lastName and address: public class Person { private String firstName; private String lastName; private String address; private String username; // The constructor method public Person(String firstName, String lastName, String address, String username) { this.firstName firstName; this.lastName lastName; this.address address; this.username username; } // The new constructor method public Person(String firstName, String lastName, String address) { this.firstName firstName; this.lastName lastName; this.address address; this.username ; } // A method to display the state of the object to the screen public void displayPersonDetails() { System.out.println(Name: firstName lastName); System.out.println(Address: address); System.out.println(Username: username); } } Note that the second constructor method is also called Person and it also does not return a value. The only difference between it and the first constructor method is the parameters – this time it expects only three string values: firstName, lastName, and address. We can now create Person objects in two different ways: public class PersonExample { public static void main(String[] args) { Person dave new Person(Dave, Davidson, 12 Main St., DDavidson); Person jim new Person(Jim,Davidson, 15 Kings Road); dave.displayPersonDetails(); jim.displayPersonDetails(); } } Person dave will be created with a firstName, lastName, address, and username. Person jim, however, will not get a username, i.e. the username will be the empty string: username . A Quick Recap Constructor methods are called only when a new instance of an object is created. They: Must have the same name as the classDo not return a valueCan have none, one, or many parametersCan number more than one as long as each constructor method has a different set of parametersCan have parameter names the same as the private fields as long as the this keyword is usedAre called using the new keyword

Characteristics Of A Parent Or A Family Member - 898 Words

Everyone has negative character traits passed on by a parent or a family member. These traits are used to define our character for this reason Sula follows in her mother foot -steps. They both love men and have a steady stream of lovers, most of whom are married to friends and neighbors. In a similar way, the two times that she has a relationship she fell hard and becomes obsessed, leaving her heart broken and devastated. Like any dysfunctional mother-daughter relationship, Hannah is similarly detached from her own daughter. As stated by Hannah, she love Sula, but she doesn t like her. In other words, she loves her daughter unconditionally but her attitude could be hard to bare. As a result, there relationship became distant. We can all agree the lack of communication is a common challenge with mothers and daughters, such as Sula and Hannah. They both have mutual hobbies and traits yet struggle to bond with each other. Many think the only way to improve the relationship is for the ot her to change their ways which is accurate in most cases.† You can’t change their actions; you can only change your own reaction and response†, stated Mintle. Specifically Sula struggle with expressing her love to her family Mothers and daughters often struggle to maintain a relationship. In Particular, Nel s family Cecile, Helene, Nel and Rochelle. Helene neglects her grandmother, Cecile who takes her away from her mother as a baby and raised her in a strict catholic household. A coupleShow MoreRelatedRelationship Between Brothers And Sisters868 Words   |  4 Pagesrelating to the relationships of siblings. Specifically, a relationship between brothers and sisters when one has a disability or developmental delay. There are many factors that affect these sibling relationships. The family system framework consists of family inputs that affect family subsystems. 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Google vs bing Free Essays

Google and Bing are competing to be the most used and talked about search engine on the Internet. To hold this title means a great deal of wealth generated from a successful search engine. The more traffic a search engine generates, the more money It can produce In the forms of endorsements and advertisements. We will write a custom essay sample on Google vs bing or any similar topic only for you Order Now In reality, competition Is good for both companies as it forces both to continually make improvements and strive to develop the best possible product for the public. This competition is one of the driving forces of our free market economy oday. The company’s history of Google has been around since the early 90’s. It was created and started as a search engine by two grad students at Stanford who major in computer science and the company has grown extremely large since its first days in Susan WoJcicki’s garage in Menlo Park. Today, Google controls the search engine landscape. A shared market survey carried out by Search Engine Land in March of 2012 found that Google controlled about 66. 4 percent of the market. Never the less, this Is a enormous percentage and Google has used its success to take hance Into many different fields away from purely Just Its search engine. Some of these may Include: videos, social media, mapping, and even creating Its own operating system. As one of the biggest technology companies on the planet, Microsoft is no foreigner to adjusting to new trends in technology. Raiseing the majority of its success and resources with the uses Windows operation system, Microsoft decided to make its own search engines that have unfolded over the years. Its current version of a search engine website is Bing. This site is a revised version f Live Search which itself came from Windows Live Search and trails all the way back to MSN search, Bing was launched in 2009, and at first it focuses on having an interactive interface with focus on searches, maps, videos, and other interactive media. Considering that this search engine Is new to the search engine world, It Is gaining prompt momentum. According to the same market share survey from Search Engine Land from March 201 2, Bing currently controls 15. percent of the search engine market. Now and days both companies now find themselves In a battle for ho can make the latest development in the battle to control the online market. Though Google owns a much higher percent of the market, Bing is gaining momentum and is now Google’s greatest competition. For the two companies that own these search engines, there are billions of dollars of resources at both the company’s fingertip s for improvement, research, and development of their products. The two companies have both attempted to make use of the social media in their continuing struggle for power, and their results are on a different path. Google has tried to start its own social media site. Google plus has linked up to Google and the company has embraced a multitude of features so the two sites can run and mesh together effectively. Microsoft went on to Join with an outside social media site. Bing has an exclusive relationship with the social media giant Facebook. The reality of this different strategy favors Bing because the popularity of Facebook Is far bigger than Google plus. As a result of this, Bing will likely continue to grow in popularity Decause 0T I users. Another area of competition that has affected the operation of the companies is the actual power of the search engines they are promoting. Google’s search algorithm gave revolution to the search engine world. It has been the driving force to the company’s success. By Bing adopting the same search algorithm has to face an opponent with, most likely the best programming in the business. To compete the search engine, Bing launched an advertisement campaign that used the classic â€Å"taste test† strategy. The idea of this campaign was for users to blindly use the two websites ( like in the commercials) for a search and then choose which engine produced a better result. Unfortunately for Bing, this strategy backfired. Though they xpected to see more users prefer their search engine, the power of the Google algorithm won the battle. According to the International Business Times, Google â€Å"came out ahead in both cases, winning 3:2 in the first test and 4:1 in the second,† A final area that the two search engines compete is their marketing gimmick. Google is an oddity among companies. It has not put much of resources into its marketing. The news got around mostly by word of mouth. Bing, on the other hand, faces a different situation. As a new, emerging search engine, it will not likely gain the popularity Google has by simply word of mouth. One strategy Bing can use is to market the differences between the two companies. They can market their social media band instead of Just claiming to be a better search engine. Competition is one of the best parts about businesses in todays free market economy. It makes companies constantly improve their products. The battle is currently wrenching between Google and Bing is another example of this fact. Both these companies are trying to make their websites constantly better than the others. The use of creative improvements to the companies has provided for continuous beneficial growth of both companies. By breaking into social media, user interfacing, videos, maps, and more, the companies are providing the public with two easy and convenient options for their search engine needs. I believe in the future we will see a shift in the strategies from the current for both companies. Google will probably back off the social media push it has made and focus more on being a knowledge based search engine that is quick, easy, and reliable. Bing will take the route of expanding its social media connections and try to show that it is a more than a user-friendly system that is great for searching within these specific domains. How to cite Google vs bing, Papers