Java基础：枚举

枚举使用enum关键字创建。所有枚举都继承自java.lang.Enum。

示例代码：

enum Transport{ //声明一个枚举
CAR(65), //
TRUCK(55),
AIRPLANE(600),
TRAIN(70),
BOAT(22);
private speed; //实例变量，保存速度
Transport(int s){speed=s;}//构造函数传递速度
int getSpeed(){return speed;}//方法获取速度
}
public class EnumDemo {
public EnumDemo() {
}
public static void main(String[] args) {
Transport tp; //声明一个Transport的引用
tp=Transport.AIRPLANE; //赋值
System.out.println("Value of tp:"+tp);
System.out.println();
tp=Transport.TRAIN;
if(tp==Transport.TRAIN) {
System.out.println("tp contains TRAIN.\n");
}
switch(tp) { //枚举常量可以控制switch语句
case CAR:
System.out.println("A car carries people.");
break;
case TRUCK:
System.out.println("A truck carries freight.");
break;
case AIRPLANE:
System.out.println("A airplane flies.");
break;
case TRAIN:
System.out.println("A train runs on rails.");
break;
case BOAT:
System.out.println("A boat sails on water.");
break;
}
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Values()和valueOf()方法：
Transport tp;
System.out.println("Here are all Transport constants");
Transport[] allTransports=Transport.values(); //values()获取枚举常量列表
for(Transport t:allTransports) {
System.out.println(t);
}
System.out.println();
tp=Transport.valueOf("AIRPLANE"); //valueOf()获取一个枚举常量
System.out.println("tp contains "+tp);
}
}
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构造函数，方法，实例变量：
System.out.println(Transports.AIRPLANE.getSpeed()); //调用方法获取速度
System.out.println("All speed in Transports");
for(Transports t:Transports.values()) {
System.out.println(t.getSpeed());
System.out.println(t+" "+t.ordinal()); //ordinal()获取顺序值
}
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