/**

 * 抽象解释器

 */

public interface AbstractExpression {

    int interptet();//处理

}

/**

 * 数字类

 */

public class NumberExpression implements AbstractExpression{

    private int number;

    public NumberExpression(int number){

        this.number = number;

    }

    @Override

    public int interptet() {

        return number;

    }

}

/**

 * 运算类

 */

public class AddExpression implements AbstractExpression{

    private AbstractExpression expression1;

    private AbstractExpression expression2;

    public AddExpression(AbstractExpression expression1,AbstractExpression expression2){

        this.expression1 = expression1;

        this.expression2 = expression2;

    }

    @Override

    public int interptet() {

        return expression1.interptet() + expression2.interptet();

    }

}

import java.util.Stack;

/**

 * 上下文，解释器

 *

 */

public class Context {

    Stack<AbstractExpression> stack = new Stack<AbstractExpression>();

    public Context(String str){

        String strs[] = str.split(" ");

        for(int i=0;i<strs.length;i++){

            switch (strs[i]){

                case "+":

                    AbstractExpression number1 = stack.pop();

                    AbstractExpression number2 = new NumberExpression(Integer.parseInt(strs[++i]));

                    stack.push(new AddExpression(number1,number2));

                    break;

                default:

                    stack.push(new NumberExpression(Integer.parseInt(strs[i])));

                    break;

            }

        }

    }

    public int calculate(){

        return stack.pop().interptet();//计算结果

    }

}

public class Main {

    public static void main(String[] args) {

        Context context = new Context("22 + 33 + 44");

        int result = context.calculate();//计算结果

        System.out.println("计算结果："+result);

    }

}