What does final mean in java?

The final keyword in Java means: once a variable is initialized, it cannot be changed; methods cannot be overridden by subclasses; classes cannot be inherited. Benefits include ensuring data integrity, improving code security, and enhancing performance.

final meaning in Java

final is a keyword in Java with the following meanings:

1. Modify variables

• Declaring a variable as final means that the value of the variable cannot be modified.
• Final variables must be initialized when declared.

final int MAX_VALUE = 100;

2. Modified method

• Declaring a method as final means that the method cannot be overridden by subclasses.
• Final methods are usually used to prevent subclasses from modifying the basic behavior in the parent class.

public final void displayMessage() {
    // 方法不能被覆盖
    System.out.println("Hello World!");
}

3. Modify the class

• Declaring the class as final means that the class cannot be subclassed.
• Final classes are typically used to create immutable types, such as String or Integer.

public final class MyClass {
    // 类不能被继承
}

Benefits:

• Ensure data integrity and prevent accidental modification of variables.
• Improve code security and prevent subclasses from modifying behavior in unpredictable ways.
• Enhance performance because the compiler can optimize final variables and methods.

Note:

• The final keyword is immutable and cannot be changed once declared.
• Final variables and methods should be used with caution to avoid limiting the flexibility of your code.

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