Java enumeration (enum) explains seven common uses

JDK1. 5 introduces a new type enumeration. Although it is a "small" function in Java, it brings "big" convenience to my development.

Usage 1: constant

At jdk1 Before 5, we defined constants as public static fianl. Now, with enumeration, you can group related constants into an enumeration type, and enumeration provides more methods than constants.

Usage 2: switch

JDK1. The switch statements before 6 only support int, char and enum types. Using enumeration can make our code more readable.

Usage 3: add a new method to the enumeration

If you want to customize your own methods, you must add a semicolon at the end of the Enum instance sequence. Moreover, Java requires that enum instances must be defined first.

Usage 4: override enumeration method

Here is an example of toString () method coverage.

Usage 5: implement interface

All enumerations are inherited from Java Lang. enum class. Because Java does not support multi inheritance, enumerated objects can no longer inherit other classes.

Usage 6: use interface to organize enumeration

Usage 7: about the use of enumeration collection

java. util. Enumset and Java util. Enummap is a collection of two enumerations. Enumset ensures that the elements in the set are not repeated; The key in enummap is of enum type, while the value can be of any type. The use of these two sets will not be described here. You can refer to the JDK documentation.

For the implementation details and principle of enumeration, please refer to:

Reference: Thinking in Java, 4th Edition http://www.jb51.net/books/75540.html

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