java_包含抽象方法的枚举类

package ming;

enum Operation {
PLUS {

public double eval(double x, double y) {
return x + y;
}

},
MINS {

public double eval(double x, double y) {
return x - y;
}

},
TIMES {

public double eval(double x, double y) {
return x * y;
}

},
DIVIDE {
public double eval(double x, double y) {
if (y == 0) {
return -1;
}
return x / y;
}
};
//为枚举类定义抽象方法，具体由枚举值提供实现
public abstract double eval(double x, double y);

}

public class OperationTest {

public static void main(String[] args) {
// TODO Auto-generated method stub
System.out.println(Operation.PLUS.eval(1, 2));
System.out.println(Operation.DIVIDE.eval(1, 0));

}

}