[use of final keyword]

Concept ： keyword final Indicates final , Immutable .

• keyword final You can modify variables 、 Method , class
• final The decorated class cannot be inherited
• When you don't want the methods of the parent class to be overwritten or overridden by subclasses, you can use final
• When you don't want the attribute to be modified, you can use final
• When you do not want a local variable to be modified, you can use final
• final The modified variable can only be assigned a value once

Use details ：

• final Modified attributes are also called constants
• final The decorated attribute must be assigned at the time of definition , And cannot be modified later , The assignment position can be found in （ Assign value when defining 、 Constructor assignment 、 Code block assignment ）, If final Decorated attributes are static , Only define time or static code block assignment can be used , Do not use constructors
• final Class cannot be inherited , But you can instantiate objects
• If the class is not final class , But there are final Method , Although this method cannot be overridden , But it can be inherited
• Generally speaking , If a class is final class , There is no need to decorate it as final The method
• final Methods cannot modify constructor , That's the constructor
• Packaging （Integer,double,float,Boolean,String All are final class ）, Unalterable