What are the Active Uses of a Class?

There are six active uses of classes that JVM should go through the initialization phase before comes to those cases.

• Process ‘new’ Keyword

For an example, create a new object of Employee, from the Company class. [Employee emp1= new Employee( ); ]

• Invoke a Static Method

For an example, Employee class has a static method called verifyEmployee( ).

So, without creating an object, you just can invoke that method from Company class. [ Employee.verifyEmployee( )]

• Assign Value for a Static Field

For an example, Employee class has a static variable called employeeCode.

So, without creating an object, you just can call that field from Company class. [ Employee.employeeCode = ‘‘executive” ]

But if that static field is final, if you access it, it will not take as an active use.

• Execute the Initial Class

If JVM is executing the class which has the main method, it is an active use.

• Invoke a Reflection Method

For an example, if you use, getInstance( ) method from Reflection API, it considers as an active use.

• Invoke Instance Subclass

For example, if you execute Manager class which is subclass of the Employee (which consist with static fields, static methods).