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non-access modifier
Java also provides many non-access modifiers in order to implement some other functions.
The static modifier is used to modify class methods and class variables.
The final modifier is used to modify classes, methods and variables. Final modified classes cannot be inherited, modified methods cannot be redefined by inherited classes, and modified variables are constants and cannot be modified.
The abstract modifier is used to create abstract classes and abstract methods.
The synchronized and volatile modifiers are mainly used for thread programming.
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static modifier
Static variables : The static keyword is used to declare static variables independent of objects. No matter how many objects a class instantiates, there is only one copy of its static variables. Static variables are also known as class variables. Local variables cannot be declared as static variables.
Static method : The static keyword is used to declare a static method independent of the object. Static methods cannot use non-static variables of the class. Static methods get data from a parameter list and then compute the data.
Access to class variables and methods can be accessed directly using class name .variablename and class name .methodname
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final modifier
final variables can be explicitly initialized and can only be initialized once. A reference to an object declared final cannot point to a different object. But the data in final objects can be changed. That is to say, the reference to the final object cannot be changed, but the value inside it can be changed.
The final modifier is usually used in conjunction with the static modifier to create class constants.
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