The final keyword in Java is one of the most useful keywords when it comes to implementing security in a program. It restricts the user from changing the values or contents declared as final. The final keyword can be used with variables, methods, and classes. In this article, we will take a look at the implementation of the final keyword in a Java program.<\/p>\n
“Final” as the name suggests, we cannot modify. When the keyword final is used before a variable, method, or class that means that it has some restrictions to prevent any changes.<\/p>\n
As the word-final suggests, we can finalize a certain entity using the final keyword. In other words, anything declared final in the Java program cannot be modified. The final keyword restricts the user’s access to modify the data.<\/p>\n
Final variables are constants that cannot be altered throughout the program. After the initialization of the final variable, it is finalized, and alteration is not possible. If we try to alter it, we will get a compilation error.<\/p>\n
The syntax for defining a final variable in Java:<\/strong><\/p>\n Code to understand the implementation of the final Variable:<\/strong><\/p>\n The output of the above code:<\/strong><\/p>\n The above code will give a compile-time error as we are trying to reassign the value of a final variable. It is impossible to do so, and hence the program won\u2019t compile.<\/p>\n We can declare a final variable and not initialize it; this type of final variable is known as a blank final variable. We have to initialize the variable in a constructor; otherwise, it will give a compilation error that the variable might not have been initialized.<\/p>\n Code to understand the implementation of the blank final Variable:<\/strong><\/p>\n The output of the above code:<\/strong><\/p>\n We might have a final variable that has a different value for different cases. In this case, if we initialize the variable at first, it will have the same value for all cases. For example, in a company, every employee has an employee ID, which is a final variable that cannot be changed. So, if we declare and initialize it at the same time, all the employees will have the same employee ID. In such cases, the employee ID is declared during object creation.<\/p>\n Code to understand the use of blank final variables:<\/strong><\/p>\n The output of the above code:<\/strong><\/p>\n We can declare a static final variable and not initialize it right away. But this variable can only be initialized in a static block inside the code.<\/p>\n Code to understand the implementation of an uninitialized static final variable:<\/strong><\/p>\n The output of the above code:<\/strong><\/p>\n We can use a final variable as a reference to an object; this is known as the reference final variable. For example, final StringBuffer S; Code to Understand Reference Final Variable:<\/strong><\/p>\n The output of the above code:<\/strong><\/p>\n A final method is a method that cannot be overridden. We can call a final method from a subclass, but the subclass cannot override the final method of the parent class. If we try to do so, it will give a compilation error.<\/p>\n Code to understand what will happen if we try to override a final method:<\/strong><\/p>\n The output of the above code:<\/strong><\/p>\n The above code didn\u2019t run as the extended class tried to override the final method, which is illegal. Let us write the code now in such a way that it runs without error.<\/p>\n Code to implement the final method properly:<\/strong><\/p>\n The output of the above code:<\/strong><\/p>\n This code did run, as the extended class only called the final method and did not try to override the final method.<\/p>\n The Java final method increases security. A final method prevents the subclass from overriding the definition of a method. If there is a method that contains a definition that should not be altered by the extended classes, it should be declared final to prevent overriding. This increases security while implementing the program.<\/p>\n When there is a class that is a stand-alone and should not be inherited in any circumstances, it should be declared final. A final class cannot be inherited whatsoever.<\/p>\n Code to understand what happens when we try to inherit a final class:<\/strong><\/p>\n The output of the above code:<\/strong><\/p>\n We can declare a parameter final, but then we will not be able to change the value of the parameter inside the method.<\/p>\n Code to understand what happens when we try to change the value of a final parameter:<\/strong><\/p>\n The output of the above code:<\/strong><\/p>\n The above code did not run because we tried to change the value of a final parameter.<\/p>\n Code to implement the final parameter properly:<\/strong><\/p>\n The output of the above code:<\/strong><\/p>\n 1. We cannot declare a constructor as final.<\/p>\n 2. Local final variables cannot be kept uninitialized.<\/p>\n 3. The default datatype of all variables in an interface is final.<\/p>\n 4. The value of a final variable is unaltered throughout.<\/p>\n 5. Overriding a final method is impossible.<\/p>\n 6. Inheriting a final class is impossible.<\/p>\n 7. A final parameter has a value that cannot be altered inside the method.<\/p>\n 8. final, finally, and finalize should not be confused as the same. They are very different concepts. finally is used in exception handling, whereas finalize is used in garbage collection.<\/p>\n While the final keyword offers advantages, it’s essential to steer clear of some common mistakes:<\/p>\n 1. Misunderstanding final parameters:<\/strong> A final parameter cannot have its value altered within the method. However, you can modify the object the parameter refers to if it’s a reference type.<\/p>\n 2. Confusing final with finally and finalize:<\/strong> These terms are distinct. Final restricts modification, finally ensures code execution even during exceptions, and finalize is invoked by the garbage collector before object removal.<\/p>\n 3. Forgetting to initialize local final variables:<\/strong> Local final variables must be assigned a value during declaration or within the same code block to prevent compilation errors.<\/p>\n In this article, we saw the use of a final keyword, and when and where we can use it. A final keyword acts as an important element when the topic is about security and imposing restrictions. Hope you understand the use and common practices of the final keyword in Java. So, start practising the final keyword and create your own runnable code.<\/p>\n","protected":false},"excerpt":{"rendered":" The final keyword in Java is one of the most useful keywords when it comes to implementing security in a program. It restricts the user from changing the values or contents declared as final....<\/p>\n","protected":false},"author":5,"featured_media":108899,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[32],"tags":[4699,4701,4703,4704,7495,16076],"class_list":["post-18872","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-java","tag-final-class-in-java","tag-final-keyword-in-java","tag-final-method-in-java-with-exmaple","tag-final-variable-in-java","tag-java-final-methods","tag-when-to-use-a-final-variable-in-java"],"yoast_head":"\nfinal <datatype> <variable name>=<value>;\/\/final variable\r\nfinal <datatype><variable name>;\/\/blank final variable\r\nstatic final <datatype><variable name>=<value>;\/\/final static variable\r\n<\/pre>\n
package com.DataFlair.Final;\r\npublic class Intern\r\n{\r\n final int SALARY=10000;\r\n void change(){ \r\n SALARY=10500;\r\n } \r\n public static void main(String args[]){ \r\n Intern i=new Intern(); \r\n i.change(); \r\n } \r\n}\r\n<\/pre>\nBlank final variable in Java<\/h3>\n
package com.DataFlair.Final;\r\npublic class Intern\r\n{\r\n final int SALARY;\r\n Intern()\r\n {\r\n SALARY=10000;\r\n }\r\n void show(){ \r\n System.out.println(SALARY);\r\n } \r\n public static void main(String args[]){ \r\n Intern i=new Intern(); \r\n i.show(); \r\n } \r\n}\r\n<\/pre>\nWhat is the use of a blank final variable?<\/h3>\n
package com.DataFlair.Final;\r\npublic class Employee\r\n{\r\n final int EMPLOYEE_ID; \r\n Employee(int eid){\r\n EMPLOYEE_ID=eid;\r\n }\r\n void show(){ \r\n System.out.println(\"The Employee ID is:\"+EMPLOYEE_ID);\r\n } \r\n public static void main(String args[]){ \r\n Employee e1=new Employee(112131221); \r\n e1.show(); \r\n }\r\n}\r\n<\/pre>\nUninitialized static final variable in Java<\/h3>\n
package com.DataFlair.Final;\r\npublic class Employee\r\n{\r\n static final int EMPLOYEE_ID; \r\n static\r\n {\r\n EMPLOYEE_ID=112131221;\r\n }\r\n void show(){ \r\n System.out.println(\"The Employee ID is:\"+EMPLOYEE_ID);\r\n } \r\n public static void main(String args[]){ \r\n Employee e1=new Employee(); \r\n e1.show(); \r\n }\r\n}\r\n<\/pre>\nReference Final Variable in Java<\/h3>\n
\nWe can change the internal state of the object that the final variable is pointing to. This doesn\u2019t mean that the property of the final variable is violated; we are not reassigning the value but changing the state of the object.<\/p>\npackage com.DataFlair.Final;\r\npublic class FinalReference\r\n{\r\n public static void main(String[] args) \r\n {\r\n final StringBuilder S = new StringBuilder(\"Data\");\r\n System.out.println(S);\r\n S.append(\"Flair\"); \r\n System.out.println(S);\r\n } \r\n}\r\n<\/pre>\n
\nDataFlair<\/div>\nJava final method<\/h3>\n
package com.DataFlair.Final;\r\npublic class Company\r\n{\r\n final void comment(){\r\n System.out.println(\"Only Company admin can access\");\r\n } \r\n} \r\npublic class Intern1 extends Company\r\n{\r\n void comment()\/\/Trying to override\r\n {\r\n System.out.println(\"Intern trying to access admin!!!!\");\r\n } \r\n public static void main(String args[]){ \r\n Intern1 i1= new Intern1(); \r\n i1.comment(); \r\n } \r\n}\r\n<\/pre>\npackage com.DataFlair.Final;\r\npublic class Company\r\n{\r\n final void comment(){\r\n System.out.println(\"Only Company admin can access\");\r\n } \r\n} \r\npublic class Intern1 extends Company\r\n{\r\n public static void main(String args[]){ \r\n Intern1 i1= new Intern1(); \r\n i1.comment(); \r\n } \r\n}\r\n<\/pre>\nPurpose of Java Final Method<\/h3>\n
Java final class<\/h3>\n
package com.DataFlair.Final;\r\nfinal public class Company\r\n{\r\n void comment(){\r\n System.out.println(\"Only Company admin can access this class!\");\r\n } \r\n} \r\npublic class Intern1 extends Company\r\n{\r\n public static void main(String args[]){ \r\n Intern1 i1= new Intern1(); \r\n i1.comment(); \r\n } \r\n}\r\n\r\n<\/pre>\nJava final parameter<\/h3>\n
package com.DataFlair.Final;\r\npublic class FinalParameter\r\n{\r\n int square(final int n)\r\n { \r\n n=n+2;\/\/can't be changed as n is final \r\n return n*n; \r\n } \r\n public static void main(String args[]){ \r\n FinalParameter p=new FinalParameter(); \r\n p.square(10); \r\n } \r\n}\r\n<\/pre>\npackage com.DataFlair.Final;\r\npublic class FinalParameter\r\n{\r\n int square(final int n)\r\n { \r\n return n*n; \r\n } \r\n public static void main(String args[]){ \r\n FinalParameter p=new FinalParameter(); \r\n int sq=p.square(10); \r\n System.out.println(sq);\r\n } \r\n}\r\n<\/pre>\nImportant points to remember:<\/h3>\n
Common Pitfalls to Avoid with the Final Keyword in Java<\/h3>\n
Conclusion<\/h3>\n