Static and Final in Java

 

Static in Java

• A static method should be called using the class name rather than object reference variables.
• A static method can be invoked without any instances of the method’s class on the heap.
• A static method is good for a utility method that does not depend on a particular instance variable value.
• A static method is not associated with a particular instance – only the class = so it cannot access any instance variable values of its class.  It wouldn’t know which instance’s values to use.
• A static method cannot access a non-static method, since non-static methods are usually associated with instance variable state.
• If you have a class with only static methods and you do not want the class to be instantiated you can mark the constructor private.
• A static variable is a variable shared by all members of a given class.  There is only one copy of a static variable in a class, rather than one copy per each individual instance for instance variables.
• A static method can access a static variable
• To make a constant in java, mark a variable as both static and final
• A final static variable must be assigned a value either at the time it is declared, or in a static initializer

 

• The naming convention for constants is to make the name all uppercase.
• A final variable value cannot be changed once it has been assigned.
• Assigning a value to a final instance variable must be either at the time it is declared, or in the constructor.
• A final method cannot be overridden.
• A final class cannot be extended (subclassed)

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