解释模式

/**解释模式
 * 用解释器模式来实现 加减乘除四则运算
 * Created by nicknailo on 2018/8/30.
 */
public class InterpretPattern {

    public static void main(String[] args) {
        Calculator calculator = new Calculator("123 + 124 + 125 - 126");
        System.out.println(calculator.calculate());


    }

}

abstract class ArithmeticExpression {
    public abstract int interptet();
}

class NumExpression extends ArithmeticExpression {
    private int num;
    public NumExpression(int _num) {
        num = _num;
    }
    @Override
    public int interptet() {
        return num;
    }
}

abstract class OperatorExpression extends ArithmeticExpression {
    protected ArithmeticExpression mArithmeticExpression1,mArithmeticExpression2;

    public OperatorExpression(ArithmeticExpression _arithmeticExpression1, ArithmeticExpression _arithmeticExpression2) {
        mArithmeticExpression1 = _arithmeticExpression1;
        mArithmeticExpression2 = _arithmeticExpression2;
    }
}

class AdditionExpression extends OperatorExpression {
    public AdditionExpression(ArithmeticExpression _arithmeticExpression1, ArithmeticExpression _arithmeticExpression2) {
        super(_arithmeticExpression1, _arithmeticExpression2);
    }

    @Override
    public int interptet() {
        return mArithmeticExpression1.interptet() + mArithmeticExpression2.interptet();
    }
}

class PlusExpression extends OperatorExpression {
    public PlusExpression(ArithmeticExpression _arithmeticExpression1, ArithmeticExpression _arithmeticExpression2) {
        super(_arithmeticExpression1, _arithmeticExpression2);
    }

    @Override
    public int interptet() {
        return mArithmeticExpression1.interptet() - mArithmeticExpression2.interptet();
    }
}


class Calculator {

    protected Stack<ArithmeticExpression> mArithmeticExpressionStack = new Stack<ArithmeticExpression>();

    public Calculator(String expression) {
        ArithmeticExpression arithmeticExpression1, arithmeticExpression2;
        String[] elements = expression.split(" ");
        for (int i = 0; i < elements.length; ++i) {
            System.out.println("elements: " + Arrays.toString(elements));
            System.out.println("elements[i]: " + elements[i].charAt(0));
            switch (elements[i].charAt(0)) {
                case '+':
                    arithmeticExpression1 = mArithmeticExpressionStack.pop();
                    System.out.println("stack.pop : = "+ arithmeticExpression1.interptet());
                    arithmeticExpression2 = new NumExpression(Integer.valueOf(elements[++i]));
                    mArithmeticExpressionStack.push(
                            new AdditionExpression(arithmeticExpression1, arithmeticExpression2));
                    break;
                case '-':
                    arithmeticExpression1 = mArithmeticExpressionStack.pop();
                    System.out.println("stack.pop : = "+ arithmeticExpression1.interptet());
                    arithmeticExpression2 = new NumExpression(Integer.valueOf(elements[++i]));
                    mArithmeticExpressionStack.push(
                            new PlusExpression(arithmeticExpression1, arithmeticExpression2));
                    break;
                default:
                    mArithmeticExpressionStack.push(new NumExpression(Integer.valueOf(elements[i])));
                    break;
            }
        }
    }

    public int calculate() {
        return mArithmeticExpressionStack.pop().interptet();
    }
}