Java Constants: Definition & Usage

In Java, constants are values that do not change during the program’s execution. The definition and usage of constants are as follows:

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final int MAX_VALUE = 100;
final String MESSAGE = "Hello";

Please note that for constant reference types, only the reference itself is guaranteed to remain constant, not the content of the referenced object.

1. The standard naming convention for constants. According to Java’s naming convention, constants are typically written in all uppercase letters and separated by underscores. For example:

final int MAX_VALUE = 100;
final String ERROR_MESSAGE = "An error occurred";

1. The use of constants. Constants can be directly used in the program without the need for assignment operations. For example:

final int MAX_VALUE = 100;
System.out.println(MAX_VALUE);  // 输出：100

It is important to note that once a constant is defined, its value cannot be changed. Attempting to modify the value of a constant will result in a compilation error. For example:

final int MAX_VALUE = 100;
MAX_VALUE = 200;  // 编译错误：无法为最终变量MAX_VALUE分配值

In summary, the definition and usage of Java constants involve using the ‘final’ keyword to declare variables and naming them following conventions. Once a constant is defined, its value cannot be changed.