ArtsAutosBooksBusinessEducationEntertainmentFamilyFashionFoodGamesGenderHealthHolidaysHomeHubPagesPersonal FinancePetsPoliticsReligionSportsTechnologyTravel

What is main in Java - why public static and void

Updated on August 17, 2012

What is main method in Java

main method in Java is an standard method from which execution of any core java program starts. when we run Java using "java" command we provide name of Class which contains standard public static void main(String args[]) method and after loading that class JVM calls this main method to start execution of Java application. Java program runs until main method is finished or any user thread created from main method is live and terminates normally when main method finished in a single thread application and when all user thread finished in a multi-threaded application. By the way this is not the first article in Java fundamentals you can also see What is PATH and CLASSPATH in Java and Difference between String and StringBuffer to learn more about fundamental topics in Java programming language.

main method is one of the fundamental things to know about Java programming language, if you are coming from C or C++ background than you must be familiar with name main() as that is also the starting point for any C and C++ application but main method in C or C++ is very different than main method in Java like return type of C and C++ main method is int while return type of Java main method is void, not just that main method in Java is public, static and void in Java and it also accept String array as argument. If you declare main method with any other signature than standard main method than JVM will not recognize that you will not be able to run your Java program and likely to get error like "no main method is found". By the way from Java 5 onwards you can also use variable arguments to replace String array as argument in Java. for example following two signature of main method is acceptable :

Signature of main method in Java

public static void main(String argument[]) and

public static void main(String... argument)

three dots at the end of String denotes variable arguments in Java.

Why main method is public static and void in Java

Since we know that main is public, static and void in Java but why? this is one of the tricky Java interview question which appears now and then in any Java interviews. let's see Why main is public, static and void in Java.

main method in Java is public so that its visible outside the class its declared. you can also see this article which discusses this topic in more detail Why main is public static and void in Java

main method is static so that it can be invoked without creating instance of the class as at the time of calling main method, JVM doesn't know how to create instance of the class which holds main method i.e. if that class contains multiple constructor than calling which constructor ?

main method is void because its not expected to return anything to JVM, main method runs under JVM and invoked by JVM not directly by operating system.

That is all about main method in Java, we have seen What is main method in Java, What is signature of main method and Why main in Java is public,static and void in Java. If you come across any other reason about main being public, static and void then post as comment.

Other Java interview articles:

Top Java Concurrency Interview Questions and Answers for Experienced

What is difference between List and Set interface in Java

Comments

    0 of 8192 characters used
    Post Comment

    No comments yet.

    working

    This website uses cookies

    As a user in the EEA, your approval is needed on a few things. To provide a better website experience, hubpages.com uses cookies (and other similar technologies) and may collect, process, and share personal data. Please choose which areas of our service you consent to our doing so.

    For more information on managing or withdrawing consents and how we handle data, visit our Privacy Policy at: https://hubpages.com/privacy-policy#gdpr

    Show Details
    Necessary
    HubPages Device IDThis is used to identify particular browsers or devices when the access the service, and is used for security reasons.
    LoginThis is necessary to sign in to the HubPages Service.
    Google RecaptchaThis is used to prevent bots and spam. (Privacy Policy)
    AkismetThis is used to detect comment spam. (Privacy Policy)
    HubPages Google AnalyticsThis is used to provide data on traffic to our website, all personally identifyable data is anonymized. (Privacy Policy)
    HubPages Traffic PixelThis is used to collect data on traffic to articles and other pages on our site. Unless you are signed in to a HubPages account, all personally identifiable information is anonymized.
    Amazon Web ServicesThis is a cloud services platform that we used to host our service. (Privacy Policy)
    CloudflareThis is a cloud CDN service that we use to efficiently deliver files required for our service to operate such as javascript, cascading style sheets, images, and videos. (Privacy Policy)
    Google Hosted LibrariesJavascript software libraries such as jQuery are loaded at endpoints on the googleapis.com or gstatic.com domains, for performance and efficiency reasons. (Privacy Policy)
    Features
    Google Custom SearchThis is feature allows you to search the site. (Privacy Policy)
    Google MapsSome articles have Google Maps embedded in them. (Privacy Policy)
    Google ChartsThis is used to display charts and graphs on articles and the author center. (Privacy Policy)
    Google AdSense Host APIThis service allows you to sign up for or associate a Google AdSense account with HubPages, so that you can earn money from ads on your articles. No data is shared unless you engage with this feature. (Privacy Policy)
    Google YouTubeSome articles have YouTube videos embedded in them. (Privacy Policy)
    VimeoSome articles have Vimeo videos embedded in them. (Privacy Policy)
    PaypalThis is used for a registered author who enrolls in the HubPages Earnings program and requests to be paid via PayPal. No data is shared with Paypal unless you engage with this feature. (Privacy Policy)
    Facebook LoginYou can use this to streamline signing up for, or signing in to your Hubpages account. No data is shared with Facebook unless you engage with this feature. (Privacy Policy)
    MavenThis supports the Maven widget and search functionality. (Privacy Policy)
    Marketing
    Google AdSenseThis is an ad network. (Privacy Policy)
    Google DoubleClickGoogle provides ad serving technology and runs an ad network. (Privacy Policy)
    Index ExchangeThis is an ad network. (Privacy Policy)
    SovrnThis is an ad network. (Privacy Policy)
    Facebook AdsThis is an ad network. (Privacy Policy)
    Amazon Unified Ad MarketplaceThis is an ad network. (Privacy Policy)
    AppNexusThis is an ad network. (Privacy Policy)
    OpenxThis is an ad network. (Privacy Policy)
    Rubicon ProjectThis is an ad network. (Privacy Policy)
    TripleLiftThis is an ad network. (Privacy Policy)
    Say MediaWe partner with Say Media to deliver ad campaigns on our sites. (Privacy Policy)
    Remarketing PixelsWe may use remarketing pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to advertise the HubPages Service to people that have visited our sites.
    Conversion Tracking PixelsWe may use conversion tracking pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to identify when an advertisement has successfully resulted in the desired action, such as signing up for the HubPages Service or publishing an article on the HubPages Service.
    Statistics
    Author Google AnalyticsThis is used to provide traffic data and reports to the authors of articles on the HubPages Service. (Privacy Policy)
    ComscoreComScore is a media measurement and analytics company providing marketing data and analytics to enterprises, media and advertising agencies, and publishers. Non-consent will result in ComScore only processing obfuscated personal data. (Privacy Policy)
    Amazon Tracking PixelSome articles display amazon products as part of the Amazon Affiliate program, this pixel provides traffic statistics for those products (Privacy Policy)