如何调试我的非常规 Java 计算器？

Question

我刚刚完成了一个计算器的编程，该计算器执行四种基本算术运算，外加六种三角运算，界面非常简约，用户只需输入表达式并显示结果，无需单独输入操作数和运算符。

我认为它可以为用户节省时间，并且看起来会更完整，因为没有更好的词了，如果它能起作用的话。

import java.util.*;

public class Calculator
{
public static String getOperator(String expression)          
{
    int counter=0;                                          

    for (int i=0; i<3; i++)                                 
    {
        if (Character.isLetter(expression.charAt(i)))      
            counter++;                                        
    }                                                      

    if (counter==3)                                       
        return expression.substring(0, 3);
    else
    {
        for (int j=0; j<expression.length(); j++)
        {
            if (Character.isDigit(expression.charAt(j))==false)
            {
              if (expression.charAt(j)!='.')
                return Character.toString(expression.charAt(j));
            }
        }
    }

    return "false";
}

public static double getFirstOperand(String operator, String expression)
{
    return Double.parseDouble(expression.substring(expression.indexOf(operator)+1));
}

public static String getOperatorType(String expression)
{
    int counter=0;

    for (int i=0; i<3; i++)
    {
        if (Character.isLetter(expression.charAt(i)))
            counter++;
    }

    if (counter==3)
        return "Trigonometrical";
    else
        return "Arithemtic";
}

public static double getResult(String operator, double operand)
{
    if (operator.equals("sin"))
        return Math.sin(operand);
    if (operator.equals("cos"))
        return Math.cos(operand);
    if (operator.equals("tan"))
        return Math.tan(operand);
    if (operator.equals("cot"))
        return 1/Math.tan(operand);
    if (operator.equals("cosec"))
        return 1/Math.sin(operand);
    else
        return 1/Math.cos(operand);      
}

public static double getSecondOperand(String expression)
{
    return Double.parseDouble(expression.substring(0, expression.indexOf(expression)));
}

public static double getResult(String operator, double operand1, double operand2)
{
    if (operator.equals("*"))
        return operand1*operand2;
    if (operator.equals("+"))
        return operand1+operand2;
    if (operator.equals("/"))
        return operand2/operand1;
    else
        return operand2-operand1;
}

public static void main(String[] args)
{
    Scanner sc = new Scanner(System.in);
    String command="", operator="", operatorType="";
    double operand1=0.0, operand2=0.0, result=0.0;

    while (command.equals("EXIT")=false)
    {
        System.out.println("Enter command: ");
        command = sc.next();

        operator = getOperator(command);
        operand1 = getFirstOperand(operator, command);
        operatorType = getOperatorType(command);

        if (operatorType.equals("Trigonometrical"))
            result=getResult(operator, operand1);
        if (operatorType.equals("Arithmetic"))
        {
            operand2 = getSecondOperand(command);
            result=getResult(operator, operand1, operand2); 
        }

        System.out.println("Result="+result);
    }
}
}

不知何故，无论我输入什么，结果总是0.0。

Enter command:
45*2
Result=0.0
Enter command:
2+2
Result=0.0

我不明白问题出在哪里。代码都找了几十遍了，就是没看到。

更新：感谢你们的帮助，伙计们。计算器终于可以正常工作了。事实上，几乎所有的问题都是由 getSecondOperand 中的一个致命错误引起的。我现在已经修复了代码，修复后的代码如下。

Answer 1

您在 getOperatorType() 中的 "Arithmetic" 中有错别字：

public static String getOperatorType(String expression)
{
    int counter=0;

    for (int i=0; i<3; i++)
    {
        if (Character.isLetter(expression.charAt(i)))
            counter++;
    }

    if (counter==3)
        return "Trigonometrical";
    else
        return "Arithemtic";
}

这就是为什么在这种情况下应避免使用字符串，而应使用 Enums。

此外，您正在使用 == 比较字符串，这是行不通的。请改用 equals()。或者，改用 Enums。

Answer 2

解决方法如下：

import java.util.*;

public class Calculator
{
public static String getOperator(String expression)
{
    int counter=0;

    for (int i=0; i<3; i++)
    {
        if (Character.isLetter(expression.charAt(i)))
            counter++;
    }

    if (counter==3)
        return expression.substring(0, 3);
    else
    {
        for (int j=0; j<expression.length(); j++)
        {
            if (Character.isDigit(expression.charAt(j))==false)
                return Character.toString(expression.charAt(j));
        }
    }

    return "false";
}

public static double getFirstOperand(String operator, String expression)
{
    return Double.parseDouble(expression.substring(expression.lastIndexOf(operator)+1));
}

public static String getOperatorType(String expression)
{
    int counter=0;

    for (int i=0; i<3; i++)
    {
        if (Character.isLetter(expression.charAt(i)))
            counter++;
    }

    if (counter==3)
        return "Trigonometrical";
    else
        return "Arithmetic";
}

public static double getResult(String operator, double operand)
{
    if (operator.equals("sin"))
        return Math.sin(operand);
    if (operator.equals("cos"))
        return Math.cos(operand);
    if (operator.equals("tan"))
        return Math.tan(operand);
    if (operator.equals("cot"))
        return 1/Math.tan(operand);
    if (operator.equals("cosec"))
        return 1/Math.sin(operand);
    else
        return 1/Math.cos(operand);      
}

public static double getSecondOperand(String expression, String operator)
{
    return Double.parseDouble(expression.substring(0, expression.indexOf(operator)));
}

public static double getResult(String operator, double operand1, double operand2)
{
    if (operator.equals("*"))
        return operand1*operand2;
    if (operator.equals("+"))
        return operand1+operand2;
    if (operator.equals("/"))
        return operand2/operand1;
    else
        return operand2-operand1;
}

public static void main(String[] args)
{
    Scanner sc = new Scanner(System.in);
    String command="", operator="", operatorType="";
    double operand1=0.0, operand2=0.0, result=0.0;
    char exitNow='0';

    while (exitNow=='0'||exitNow=='N')
    {
        System.out.println("Enter command: ");
        command = sc.next();

        operator = getOperator(command);
        operand1 = getFirstOperand(operator, command);
        operatorType = getOperatorType(command);

        if (operatorType.equals("Trigonometrical"))
            result=getResult(operator, operand1);
        if (operatorType.equals("Arithmetic"))
        {
            operand2 = getSecondOperand(command, operator);
            result=getResult(operator, operand1, operand2); 
        }

        System.out.println("Result="+result+"\nExit now(1/0)(Y/N)");
        exitNow=sc.next().charAt(0);            
    }
}
}

如何调试我的非常规 Java 计算器？

How to debug my unconventional Java calculator?

java

debugging

calculator