Java 枚举(enum) 常见用法

用法一：常量

public enum Color{
RED,GREEN,BLANK,YELLOW
}

用法二：switch

enum Signal{
GREEN,YELLOW,RED
}
public class TrafficLight{
public void change(Color color){
switch(color){
case RED:
System.out.println("red");
break;
case GREEN:
System.out.println("green");
break;
}
}
}

用法三：向枚举中添加新方法

enum Color{
RED("red",1),GREEN("绿色",2);
//成员变量
private String name;
//构造方法
private Color(String name,int index){
this.name = name;
this.index = index;
}
//普通方法
public static String getName(int index){
for(Color color:Color.values()){
if(color.getIndex() == index){
return c.name;
}
}
return null;
}
// get set 方法
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getIndex() {
return index;
}
public void setIndex(int index) {
this.index = index;
}
}

用法四：覆盖枚举的方法

public enum Color {
RED("红色", 1), GREEN("绿色", 2), BLANK("白色", 3), YELLO("黄色", 4);
// 成员变量
private String name;
private int index;
// 构造方法
private Color(String name, int index) {
this.name = name;
this.index = index;
}
//覆盖方法
@Override
public String toString() {
return this.index+"_"+this.name;
}
}

用法五：实现接口

public interface Behaviour {
void print();
String getInfo();
}
public enum Color implements Behaviour{
RED("红色", 1), GREEN("绿色", 2), BLANK("白色", 3), YELLO("黄色", 4);
// 成员变量
private String name;
private int index;
// 构造方法
private Color(String name, int index) {
this.name = name;
this.index = index;
}
//接口方法
@Override
public String getInfo() {
return this.name;
}
//接口方法
@Override
public void print() {
System.out.println(this.index+":"+this.name);
}
}

用法六：使用接口组织枚举

public interface Food {
enum Coffee implements Food{
BLACK_COFFEE,DECAF_COFFEE,LATTE,CAPPUCCINO
}
enum Dessert implements Food{
FRUIT, CAKE, GELATO
}
}

用法七：定义枚举值自己的方法

enum Color {
Red {
public String toString() {
return "Color.Red";
}
},
Green {
public String toString() {
return "Color.Green";
}
},
Blue {
public String toString() {
return "Color.Blue";
}
};
}

用法八：实现单例

class Test{}
enum Singleton {
INSTANCE;
private Test test;
private Singleton() {
test = new Test();
}
public Test getInstance() {
return test;
}
}