final ???? Java?? ??? ???? ???? ???? ?? ???? ?? ? ?????. ??? ?? ?? ??? ? ?? ??? ???? ? ?????. ? ?????? ??? ???? final ???? ?? ??? ??, ?? ?? ? ???? ??? ??? ???????.

1. ??? ??? ??

??? ?? final? ???? ?? ???? ??? ??? ? ????. ??? ??? ??? ????.

• ?? ?? ??: ??? ??? ?????(?: COUNT).
• ??? ?? ??: ???? ???
?? ????? ???.
• ?? ???? ????? ???: ????? ????? ?? ?? ???? ?? ???? ???.
• ?? ??: ?? ??? ??? ? ???? ?? ??? ?? ??? ??? ? ????.

final int COUNT;  
final char GENDER = 'F'; // Initialized at declaration

public FinalKeyword() {
  // Initialized in Constructor
  COUNT = 90;

  // This will give a compile error
  // once initialized during declaration, cannot be changed
  GENDER = 'M'; 
}

?? ???:

• COUNT? ?? ? ????? ????. ? ????? ????? ???.
• GENDER? 'F'? ????? ?? ???? ??? ? ????.

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2. ?? ??? ??? ??

?? ?? ??? ?? ? ?? ?? ???? ?????? ???. ???? ??? ?? ?? ?? ??? ??? ?? ??? ????? ???? ? ????.

• ?? ??? ?? ????? ?? ???? ????.
• Final? ???? ?????. ?, ?? ?? ????? ???? ??? ? ????.

static final int ID = 1;  
static final int DEPT;  

static {
    DEPT = 90; // Initialized in static block
}

????? ?? ?? ??? ???? ? ?? ??? ??????

????? ??? ? ???? ???? ?? ??? (????? ??) ???? ????? ??? ??? ?????? ??? ? ????.

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3. ?? ??? ?? ?? ??

final? ???? ??? ??? ????? ??? ? ????.

static int salary; // Default value 0 at class loading

public FinalKeyword() {
    salary = 10; // Static variable modified in constructor
}

Key Differences

• Static variables are shared across instances and can be modified by any of them.
• Static final variables are immutable and shared by all instances, ensuring they remain constant throughout the program.

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4. Constructor Requirements for Final Variables

When a final variable is not initialized at the time of declaration, it must be initialized in all constructors to avoid a compile-time error.

public FinalKeyword() {
    COUNT = 90; // Initialized in default constructor
}

public FinalKeyword(int count) {
    COUNT = count; // Initialized in parameterized constructor
}

If a constructor does not initialize a final variable, the compiler will throw an error, ensuring the value is always assigned exactly once.

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4. Comparison of Final Keyword Usage in Methods and Classes

• Final Methods: A final method ensures that subclasses cannot override it, enforcing consistent behavior across all instances. This is useful for methods like getType() in Object, which ensures critical functionality is not altered.

• Final Classes: Declaring a class as final (e.g., String or Math) ensures that no subclass can alter its behavior, maintaining data integrity and preventing misuse.

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Conclusion

The final keyword is a powerful tool in Java to enforce immutability and prevent unintended modifications. It plays a crucial role in defining constants, ensuring class-level consistency, and making code easier to understand and maintain.

Stay tuned for other posts in this series, where we’ll cover more Java keywords in depth to help you master the nuances of the language!

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Related Posts

• Java Fundamentals

• Array Interview Essentials

• Java Memory Essentials

• Collections Framework Essentials

Happy Coding!

? ??? Java? ?? ??? ?????: ??, ??? ?? ?? ?????. ??? ??? PHP ??? ????? ?? ?? ??? ?????!