Usage of enum in java

Enumerations are used in Java to define a limited set of constants, providing features such as singleton, immutability, and comparability. Specific usage methods include: defining enumerations, obtaining enumeration constant names and order, obtaining constants by name, and comparing constants. Enumerations are often used to represent a limited set of options for colors, seasons, file types, etc.

Usage of enumerations in Java

Enumerations are used in Java to represent fixed and limited set values. of a type. It provides a safe and reliable way to deal with a predefined set of constants.

How to use enumerations

To define an enumeration, use the enum keyword, followed by the name of the enumeration:

<code class="java">enum Color {
  RED,
  GREEN,
  BLUE
}</code>

This creates three enumeration constants: RED, GREEN, and BLUE.

Characteristics of enumerations

• Single case: Each enumeration constant is a singleton object, which means that it There is only one instance.
• Immutable: Once an enumeration constant is created, it cannot be modified.
• Comparability: Enumeration constants can be safely compared using the == and != operators.

Uses of enumerations

Enumerations are often used to represent a limited set of options, for example:

• Color
• Season
• File Type
• HTTP Status Code

Enumeration Methods

Enumeration provides The following useful methods:

• #name(): Returns the name of the enumeration constant.
• ordinal(): Returns the order of the enumeration constants in the enumeration (starting from 0).
• valueOf(String name): Get the enumeration constant by name.

Example

The following example shows how to use enumerations:

<code class="java">enum Color {
  RED,
  GREEN,
  BLUE
}

public class Main {
  public static void main(String[] args) {
    Color color = Color.RED;

    // 打印枚举常量的名称
    System.out.println(color.name()); // 输出：RED

    // 打印枚举常量的顺序
    System.out.println(color.ordinal()); // 输出：0

    // 通过名称获取枚举常量
    Color otherColor = Color.valueOf("GREEN");

    // 比较两个枚举常量
    if (color == otherColor) {
      System.out.println("两个颜色相等");
    }
    else {
      System.out.println("两个颜色不相等");
    } // 输出：两个颜色不相等
  }
}</code>

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