directionvalue.java

是有关解释器的.用JAVA编写.可以解释一般的JAVA程序.

public class DirectionValue extends Value {
    private String value;

    DirectionValue() {
        value = "North";
    }

    DirectionValue(String s) {
        value = s;
    }

    boolean isDirection() {
        return true;
    }

    String directionValue() {
        return value;
    }

    boolean isOfType(String typeName) {
        return typeName.equals("direction");
    }

    int numberValue() {
        if (value.equals("North"))
            return direction.NORTH_VALUE;
        else if (value.equals("East"))
            return direction.EAST_VALUE;
        else if (value.equals("South"))
            return direction.SOUTH_VALUE;
        else
            return direction.WEST_VALUE;

        // could check for "West", too and throw an exception if it's not "West"
        // either
        // but it schould be redundant
    }

    direction primitiveDirectionValue() {
        if (value.equals("North"))
            return direction.NORTH;
        else if (value.equals("East"))
            return direction.EAST;
        else if (value.equals("South"))
            return direction.SOUTH;
        else
            return direction.WEST;
    }

    public String toString() {
        return value;
    }

    Value isEqual(Value v) throws InterpreterException {
        if (!v.isDirection())
            throw new InterpreterException(
                    "This type does not support equation.");

        return new BooleanValue(value.equals(((DirectionValue) v)
                .directionValue()));
    }

    Value assign(Value v) throws InterpreterException {
        if (!v.isDirection())
            throw new InterpreterException("wrong type.");

        this.value = ((DirectionValue) v).directionValue();
        return this;
    }

    Value cloneValue() {
        return new DirectionValue(value);
    }
}