基于控制台的命令处理：将字符串映射到Java中的枚举

Question

For my java console application, I need to call a set of functions with user given arguments. My operations O1, O2, .. O5 are defined as an enum as

enum Operations {O1, O2, O3, O4, O5};

I need to read user input args[0] and call function F1, F2,...F5.

For example user is going to give:

>java MyApp O1 5 6

For this I suppose I need to map sting (args[0]) to an enum so that I can use switch select. How to do this?

Answer 1

Enum.valueOf(Class, String) .

Example

Operations oper = Enum.valueOf(Operations.class, args[0]);

Will throw an exception if there are no enum values that matches args[0]

Answer 2

I suppose using what chuk lee 's lead you can come up with pritty cool program here what I did.

public class Main {


public static void main(String[] args) {

    if(args.length < NUMBER_OF_OPERATORS){
         throw new IllegalArgumentException(INSUFFICIENT_OPERANDS); 
    }

    Operator operator = Enum.valueOf(Operator.class,
                                         args[OPERATION_NAME].toUpperCase());

    System.out.println(operator.operate(args[FIRST_OPERAND],
                                                   args[SECOND_OPERAND]));


}


private enum Operator {

    ADD,SUBSTRACT,MULTIPLY,DIVIDE;

    public String operate(String aString, String bString) {

        int a = Integer.valueOf(aString);
        int b = Integer.valueOf(bString);

        int out = 0;


        switch(this) {


            case ADD    : out = a + b; break;
            case SUBSTRACT  : out = a - b; break;
            case MULTIPLY   : out = a * b; break;
            case DIVIDE : out = a / b; break;
            default: throw new UnsupportedOperationException();
        }

        return String.valueOf(out);
    }

}

private static final int NUMBER_OF_OPERATORS = 3;
private static final int OPERATION_NAME = 0;
private static final int FIRST_OPERAND = 1;
private static final int SECOND_OPERAND = 2;
private static final String INSUFFICIENT_OPERANDS = 
                           "Insufficient operads to carry out the operation.";

}