mini dc与简易计算器 20165235

Posted 2020-11-04 qy20165235

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mini dc

任务内容

本次mini dc任务就是通过补充代码来实现整型数据的后缀表达式计算

实现代码

import java.util.Stack;
import java.util.StringTokenizer;
import java.util.*;
public class MyDC
{
/** constant for addition symbol */
private final char ADD = ‘+‘;
/** constant for subtraction symbol */
private final char SUBTRACT = ‘-‘;
/** constant for multiplication symbol */
private final char MULTIPLY = ‘*‘;
/** constant for division symbol */
private final char DIVIDE = ‘/‘;
/** the stack */
private Stack<Integer> stack;
   // MyDC my= new MyDC();
public MyDC() {
    stack = new Stack<Integer>();
}

public int evaluate (String expr)
{
    int op1, op2, result = 0;
    String token;
    StringTokenizer tokenizer = new StringTokenizer (expr);
    while (tokenizer.hasMoreTokens())
        {
        token = tokenizer.nextToken();
            //System.out.println(token);
        //如果是运算符，调用isOperator
        if (isOperator(token))
        {
            char []c=token.toCharArray();
            op1=stack.pop();
            //从栈中弹出操作数2
            op2=stack.pop();
            //从栈中弹出操作数1
            result=evalSingleOp(c[0],op1,op2);
            //根据运算符和两个操作数调用evalSingleOp计算result;
            stack.push(result);
            //计算result入栈;
        }
        else{
            //如果是操作数
            if(token.matches("[0-9]+")) {
                int number=Integer.parseInt(token);
                stack.push(number);
            }
        }
    }
    return result;
}

private boolean isOperator (String token)
{
    return ( token.equals("+") || token.equals("-") ||
            token.equals("*") || token.equals("/") );
}

private int evalSingleOp (char operation, int op1, int op2)
{
    int result = 0;

    switch (operation)
    {
        case ADD:
            result = op1 + op2;
            break;
        case SUBTRACT:
            result = op1 - op2;
            break;
        case MULTIPLY:
            result = op1 * op2;
            break;
        case DIVIDE:
            result = op1 / op2;
    }

    return result;
}
}

代码运行截图

技术分享图片

简易计算器

任务内容

实现一个简易计算器Calc,支持+ - x /和%运算, 从命令行传入计算数据，Calc计算器可以进行简单的计算。

实现代码

import java.io.IOException;
import java.util.*;
public class CalczOperator  {
    /** constant for addition symbol */
    private final char ADD = ‘+‘;
    /** constant for subtraction symbol */
    private final char SUBTRACT = ‘-‘;
    /** constant for multiplication symbol */
    private final char MULTIPLY = ‘x‘;
    /** constant for division symbol */
    private final char DIVIDE = ‘/‘;
    /** constant for MOD symbol */
    private final char MOD = ‘%‘;
    /** the stack */
    Stack<Integer> stack=new Stack<Integer>();
    Stack<Character> stack1=new Stack<Character>();
     int operate(String str)throws IOException {
        int op1,op2,result=0;
        int i=0;
        String string;
        StringTokenizer fenxi=new StringTokenizer(str);
        while (fenxi.hasMoreTokens())
        {
            string = fenxi.nextToken();
            //如果是运算符，调用isOperator
            if (isOperator(string))
            {
                char c[]=string.toCharArray();
                stack1.push(c[0]);
            }
            else{
                //如果是操作数
                if(string.matches("[0-9]+")) {
                    i++;
                    int number=Integer.parseInt(string);
                    stack.push(number);
                    if(i==2){
                        op1=stack.pop();
                        op2=stack.pop();
                        result=result=evalSingleOp(stack1.pop(),op2,op1);
                    }
                }
            }
        }
        return result;
    }
private int evalSingleOp (char operation, int op1, int op2)
        {
        int result = 0;

        switch (operation)
        {
        case ADD:
        result = op1 + op2;
        break;
        case SUBTRACT:
        result = op1 - op2;
        break;
        case MULTIPLY:
        result = op1 * op2;
        break;
        case DIVIDE:
        result = op1 / op2;
        break;
        case MOD:
        result = op1 % op2;
        break;
        }

        return result;
        }
 private boolean isOperator (String token)
    {
        return ( token.equals("+") || token.equals("-") ||
                token.equals("x") || token.equals("/") ||token.equals("%"));
    }

}

import java.io.IOException;
public class Calc  {
    public static void main (String args[]){
        try {
            CalczOperator calczoperator = new CalczOperator();
            String[] prt = new String[args.length];
            for(int i =0;i<args.length;i++){
                prt[i] = args[i];
            }
            String str = prt[0]+" "+prt[1]+" "+prt[2]
            int result = calczoperator.operate(str);
            System.out.println(str + " = " + result);
        }
        catch (IOException e){
            System.out.println("error");
        }
    }
}

代码运行截图：

技术分享图片

遇到的问题以及解决过程

当运行代码java Calc 3 * 2，时报错，对其他的运算符都能正常运行出结果，只有*运算符不可以，我在Ubuntu和Windows的命令行中都运行了一遍，但都会报错。
技术分享图片
我通过JDB调试，print args[]中的数值时，args[1]，args[2]的数据出错。