设计模式-解释器模式(下)

package com.example.designpattern.interpret.hard;

/**
 * @Author: zhangQi
 * @Date: 2021-02-10 11:25
 */
public interface Expression {
    long interpret();
}

package com.example.designpattern.interpret.hard;


/**
 * @Author: zhangQi
 * @Date: 2021-02-10 11:26
 */
public class NumberExpression implements Expression{

    private long number;

    public NumberExpression(long number){
        this.number = number;
    }

    public NumberExpression(String number){
        this.number = Long.parseLong(number);
    }

    @Override
    public long interpret() {
        return this.number;
    }


}

package com.example.designpattern.interpret.hard;


/**
 * @Author: zhangQi
 * @Date: 2021-02-10 11:27
 */
public class AdditionExpression implements Expression{
    private Expression exp1;
    private Expression exp2;

    public AdditionExpression(Expression exp1,Expression exp2){
        this.exp1 = exp1;
        this.exp2 = exp2;
    }

    @Override
    public long interpret() {
        return exp1.interpret()+exp2.interpret() ;
    }

}

package com.example.designpattern.interpret.hard;

/**
 * @Author: zhangQi
 * @Date: 2021-02-10 12:22
 */
public class SubstractionExpression implements Expression{
    private Expression exp1;
    private Expression exp2;

    public SubstractionExpression(Expression exp1, Expression exp2){
        this.exp1 = exp1;
        this.exp2 = exp2;
    }

    @Override
    public long interpret() {
        return exp1.interpret()-exp2.interpret() ;
    }
}

package com.example.designpattern.interpret.hard;


/**
 * @Author: zhangQi
 * @Date: 2021-02-10 12:23
 */
public class MultiplicationExpression implements Expression{
    private Expression exp1;
    private Expression exp2;

    public MultiplicationExpression(Expression exp1,Expression exp2){
        this.exp1 = exp1;
        this.exp2 = exp2;
    }

    @Override
    public long interpret() {
        return exp1.interpret()*exp2.interpret() ;
    }

}

package com.example.designpattern.interpret.hard;

/**
 * @Author: zhangQi
 * @Date: 2021-02-10 12:23
 */
public class DivisionExpression implements Expression{
    private Expression exp1;
    private Expression exp2;

    public DivisionExpression(Expression exp1,Expression exp2){
        this.exp1 = exp1;
        this.exp2 = exp2;
    }

    @Override
    public long interpret() {

        try {
            return exp1.interpret()/exp2.interpret();
        } catch (ArithmeticException e) {
            if(exp2.interpret()==0){
                System.out.print("除数不能为0,默认返回Long最大值:");
            }
            return Long.MAX_VALUE;
        }
    }
}

package com.example.designpattern.interpret.hard;

import java.util.ArrayList;
import java.util.Deque;
import java.util.LinkedList;
import java.util.List;

/**
 * @Author: zhangQi
 * @Date: 2021-02-10 12:26
 */
public class ExpressionInterpreter {
    private Deque<Expression> numbers = new LinkedList<>();

    public long interpret(String expression){
        String[] elements = expression.split(" ");
        int length = elements.length;
        for(int i=0;i<(length+1)/2;++i){
            numbers.addLast(new NumberExpression(elements[i]));
        }
        for(int i=(length+1)/2;i<length;++i){
            String operator = elements[i];
            boolean isValid = "+".equals(operator) || "-".equals(operator)
                    || "*".equals(operator) || "/".equals(operator);
            if(!isValid){
                throw new RuntimeException("Expression is invalid: "+expression);
            }

            Expression exp1 = numbers.pollFirst();
            Expression exp2 = numbers.pollFirst();
            Expression combindExp = null;
            if(operator.equals("+")){
                combindExp = new AdditionExpression(exp1,exp2);
            }else if(operator.equals("-")){
                combindExp = new SubstractionExpression(exp1,exp2);
            }else if(operator.equals("*")){
                combindExp = new MultiplicationExpression(exp1,exp2);
            }else if(operator.equals("/")){
                combindExp = new DivisionExpression(exp1,exp2);
            }
            long result = combindExp.interpret();
            numbers.addFirst(new NumberExpression(result));
        }

        if(numbers.size()!=1){
            throw new RuntimeException("Expression is invalid: "+expression);
        }

        return numbers.pop().interpret();
    }

    public static void main(String[] args) {
        ExpressionInterpreter cal = new ExpressionInterpreter();
        String behindExpression1 = "3 3 +";
        String behindExpression2 = "3 3 1 4 + - *";
        String behindExpression3 = "5 3 1 4 0 - - * /";
        String behindExpression4 = "2 3 1 4 0 9 * - * + +";
        List<String> behindExpressionList = new ArrayList<>();
        behindExpressionList.add(behindExpression1);
        behindExpressionList.add(behindExpression2);
        behindExpressionList.add(behindExpression3);
        behindExpressionList.add(behindExpression4);
        behindExpressionList.forEach(bhex-> System.out.println(cal.interpret(bhex)));
    }
}