{"id":6554,"date":"2024-04-21T23:55:07","date_gmt":"2024-04-22T06:55:07","guid":{"rendered":"https:\/\/zentut.com\/java-tutorial\/java-final-class\/"},"modified":"2024-04-21T23:55:32","modified_gmt":"2024-04-22T06:55:32","slug":"java-final-class","status":"publish","type":"page","link":"https:\/\/www.zentut.com\/java-tutorial\/java-final-class\/","title":{"rendered":"Java Final Class"},"content":{"rendered":"\n

Summary<\/strong>: in this tutorial, you will learn about the Java final class and how to use it to define classes that cannot be inherited.<\/p>\n\n\n\n

Introduction to Java final class<\/h2>\n\n\n\n

In Java, a final class cannot be inherited<\/a>. When you define a class<\/a> as final, you’re stating that it is complete and should not be extended.<\/p>\n\n\n\n

In practice, you often use the final classes to encapsulate functionality that should remain unchanged.<\/p>\n\n\n\n

To create a final class in Java, you use the final<\/code> keyword as follows:<\/p>\n\n\n

final<\/span> class<\/span> MyFinalClass<\/span> <\/span>{\n    \/\/ Class members and methods<\/span>\n}<\/code><\/span>Code language:<\/span> Java<\/span> (<\/span>java<\/span>)<\/span><\/small><\/pre>\n\n\n
In this syntax, the MyFinalClass<\/code> is final. If you attempt to extend it, you’ll get an error:<\/p>\n\n\n
\/\/ Error: Cannot inherit from final 'Calculator'<\/span>\nclass<\/span> Subclass<\/span> extends<\/span> MyFinalClass<\/span> <\/span>{\n}<\/code><\/span>Code language:<\/span> Java<\/span> (<\/span>java<\/span>)<\/span><\/small><\/pre>\n\n\n
Java final class example<\/h2>\n\n\n\n
The following example shows how to define the Calculator<\/code> class as a final class:<\/p>\n\n\n
final<\/span> class<\/span> Calculator<\/span> <\/span>{\n    public<\/span> static<\/span> double<\/span> add<\/span>(double<\/span> a, double<\/span> b)<\/span><\/span>{\n        return<\/span> a + b;\n    }\n    public<\/span> static<\/span> double<\/span> subtract<\/span>(double<\/span> a, double<\/span> b)<\/span><\/span>{\n        return<\/span> a - b;\n    }\n\n    public<\/span> static<\/span> double<\/span> divide<\/span>(double<\/span> a, double<\/span> b)<\/span><\/span>{\n        return<\/span> a \/ b;\n    }\n\n    public<\/span> static<\/span> double<\/span> multiply<\/span>(double<\/span> a, double<\/span> b)<\/span><\/span>{\n        return<\/span> a * b;\n    }\n}<\/code><\/span>Code language:<\/span> Java<\/span> (<\/span>java<\/span>)<\/span><\/small><\/pre>\n\n\n
The Calculator<\/code> class contains four static methods that perform basic mathematical operations including addition, subtraction, multiplication, and division. <\/p>\n\n\n\n
You can use the final Calculator<\/code> class throughout your application without the risk of accidentally extending it or modifying its behavior.<\/p>\n\n\n\n
Java final class use cases<\/h2>\n\n\n\n
You use final classes when you want to ensure a certain classes of your codebase remain unchanged.<\/p>\n\n\n\n
Here are some common use cases of the final classes:<\/p>\n\n\n\n
    \n
  • Utility Classes<\/strong>: Classes that contain static utility methods often make good final classes because the utility methods should not be extended.<\/li>\n\n\n\n
  • Immutable Classes<\/strong>: Classes representing immutable objects (objects whose state cannot be changed after creation) are often declared as final to guarantee their immutability.<\/li>\n\n\n\n
  • Security<\/strong>: Final classes can be used to prevent tampering with critical code in security-sensitive applications.<\/li>\n<\/ul>\n\n\n\n
    Final classes in Java SE<\/h2>\n\n\n\n
    Java standard library has many built-in final classes. These classes cannot be extended because if you do so,  their intended use would now make sense.<\/p>\n\n\n\n
    For example, the String (java.lang<\/code>.String) is a final class because the string is immutable. Therefore, you cannot make an extended version of the String class via inheritance like this:<\/p>\n\n\n
    \/\/ error<\/span>\nclass<\/span> MyString<\/span> extends<\/span> String<\/span> <\/span>{\n}<\/code><\/span>Code language:<\/span> Java<\/span> (<\/span>java<\/span>)<\/span><\/small><\/pre>\n\n\n
    Another example of a utility class, which is a final class, is the Math class (java.lang<\/code>.Math). The Math class provides a static method for performing mathematical operations is a final class:<\/p>\n\n\n
    public<\/span> final<\/span> class<\/span> Math<\/span> <\/span>{\n \/\/ ...<\/span>\n}<\/code><\/span>Code language:<\/span> Java<\/span> (<\/span>java<\/span>)<\/span><\/small><\/pre>\n\n\n
    Summary<\/h2>\n\n\n\n
      \n
    • Define a class as final if you don’t want it to be extended.<\/li>\n\n\n\n
    • Use Java final classes for utility or immutable classes.<\/li>\n<\/ul>\n","protected":false},"excerpt":{"rendered":"
      Summary: in this tutorial, you will learn about the Java final class and how to use it to define classes that cannot be inherited. Introduction to Java final class In Java, a final class cannot be inherited. When you define a class as final, you’re stating that it is complete and should not be extended. […]<\/p>\n","protected":false},"author":2,"featured_media":0,"parent":2190,"menu_order":37,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-6554","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/www.zentut.com\/wp-json\/wp\/v2\/pages\/6554","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.zentut.com\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/www.zentut.com\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/www.zentut.com\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.zentut.com\/wp-json\/wp\/v2\/comments?post=6554"}],"version-history":[{"count":2,"href":"https:\/\/www.zentut.com\/wp-json\/wp\/v2\/pages\/6554\/revisions"}],"predecessor-version":[{"id":6556,"href":"https:\/\/www.zentut.com\/wp-json\/wp\/v2\/pages\/6554\/revisions\/6556"}],"up":[{"embeddable":true,"href":"https:\/\/www.zentut.com\/wp-json\/wp\/v2\/pages\/2190"}],"wp:attachment":[{"href":"https:\/\/www.zentut.com\/wp-json\/wp\/v2\/media?parent=6554"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}