In the above example, zi can modify Fu's show() function
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final can modify classes, methods, variables
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A. Modifiers
The bottom-level class is generally modified with final, "sterilized" and cannot have subclasses.
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B. Modification methods
This method cannot be overridden, or overridden
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B. Modified variables
The variable cannot be recopied because the variable is actually a constant
There are two types of constants:
A literal constant: 10, true, "hello"
B custom constant: final int x = 10;
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final decorates local variables:
1) Local variables are primitive data types
1) Local variables are reference types
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The timing of initialization of final modified variables:
---Final modified variables can only be assigned once
--- Occurs before the completion of the construction method (non-static constants, statics are already initialized when the class is loaded)
