Where are static final variables used in java?

Question

I am studying java and wanted to know what's the usage of static final variables in application designing. Please provide some examples too.

Answer 1

Uses of a static final variable :

1. To define a compile time constant value. eg : The Integer class defines a constant called MIN_VALUE as : public static final int MIN_VALUE = 0x80000000;
2. To create a non modifiable reference that can be accessed globally : Eg The Singleton pattern using a public static final reference.

When you mark a variable defined in a class as static , it is shared across all the instances of a class . When you mark a variable in a class as final , it can only be initialized once either on the same line as the declaration of the variable or in the constructor of the class. Putting both together, a member static final variable is shared across all instances of a class , must be initialized where it is declared, and cannot be modified once declared.

Answer 2

final means the reference can't be changed once it's set. static means the variable belongs to a class , not a specific instance . This combination of modifiers, especially when used on a primitive or an immutable class (such as String ) are often used to represent constants. A classic example would be java.io.File.separtorChar .

Answer 3

您可以像这样定义常量

public static final String LANGUAGE = "JAVA"