How are Java constants defined?

In Java, constants can be defined using the keyword final. The value of a constant cannot be changed after it is defined.

Constant names are typically written in uppercase letters, with underscores separating multiple words, for example:

final int MAX_NUMBER = 10; // 定义一个整型常量，值为10
final double PI = 3.14; // 定义一个浮点型常量，值为3.14
final String GREETING = "Hello"; // 定义一个字符串常量，值为"Hello"

Please be aware:

1. After a constant is defined, it cannot be reassigned.
2. Constants are typically defined at the top of a class as class attributes.
3. Constants can be defined within a method, but can only be used within that method.

If you want constants to be accessible in other classes, you can use the public or static keyword for modification.

public static final int MAX_NUMBER = 10; // public和static修饰的常量可以在其他类中访问

Using constants can improve the readability and maintainability of code by defining some fixed values as constants, making it easier to modify and maintain the code.