字符串数学算法出错 JavaFX

Question

当我构建我的第一个JavaFX项目时，我注意到我构建的计算器引擎有点不对劲。话虽如此，我现在检查了大约一个小时的代码，试图找出问题所在，但我找不到任何与我的程序中这个奇怪错误相关的内容。

计算器引擎：

public static String BasicEval(String str, String function) {
int indexOfOperation = str.indexOf(function);
int downBoundary = indexOfOperation - 1;
int upBoundary = indexOfOperation + 1;
int closestUp = str.length(), closestDown = 0;
for (int index = 0; index < str.length(); index++) { // Searching for the closest white space (between vals.) to determine what are the two vals.
if (Math.abs(indexOfOperation - index) == 1) {
continue;
} else if ((str.charAt(index) == ' ') && ((indexOfOperation - index) > closestDown)) {
closestDown = index; //Finds the closest blank space in order to differentiate between elements.
} else if ((str.charAt(index) == ' ') && (Math.abs(indexOfOperation + index) < closestUp)) {
closestUp = index; //Finds the closest black space in order to differentiate between elements.
}
}
while (str.substring(upBoundary,closestUp).contains("X") || (str.substring(upBoundary,closestUp).contains("-") || (str.substring(upBoundary,closestUp).contains("+") || (str.substring(upBoundary,closestUp).contains("/") || (str.substring(upBoundary,closestUp).contains("^")))))) {
closestUp--;
}
double firstValue = Double.valueOf(str.substring((closestDown + 1), downBoundary));
double secondValue = Double.valueOf(str.substring(upBoundary + 1, (closestUp-1)));
double OperationResult;
switch (function) {
case "^" : OperationResult = Math.pow(firstValue,secondValue); break;
case "X" : OperationResult = (firstValue * secondValue); break;
case "/" : OperationResult = (firstValue / secondValue); break;
case "+" : OperationResult = (firstValue + secondValue); break;
case "-" : OperationResult = firstValue - secondValue; break;
default: OperationResult = -999.12349876; //ERROR
}
str = strSort(str,firstValue,secondValue,OperationResult);
return str;
}

关于引擎的一点：引擎本身假设计算字符串中的数学表达式，因此例如输入将是："3 + 4"，答案将是：7.0作为双精度。我希望实现这一目标的方法是通过术语和操作符号之间的空格将str分成4个较小的部分。问题是：当你使用更大的数字时，数学变得很奇怪。数字 -999.123...代表我的程序中的错误。

该引擎适用于使用低数字的简单计算，但是当您开始使用较大的数字时，事情会变得混乱。有时它还会产生诸如"空字符串"之类的错误，我不明白为什么..

有关项目或引擎的更多信息，请发表评论。 -- 请记住，我正在寻找一个适用于我的算法的答案，而不是一般的 javaFX -- (尽管我很想学习新东西( 谢谢！！

事情如何不像它们应该的那样的例子： 在此处输入图像描述 在此处输入图像描述

我会在评论中发布更多图片。

strSort Method

public static String strSort(String str, double firstValue, double secondValue, double result) {
//Method that sorts between which vals are ints and which ones are doubles. --> returns them in their current form.
int firstValueIndex = 0;
int secondValueIndex = 0;
if (!intOrDoubleTest(firstValue) && firstValue == secondValue){ // Special category : indexOf doesn't work since the two vals. are the same --> giving off the same index.
firstValueIndex = str.indexOf(Double.toString(firstValue));
secondValueIndex = str.indexOf(Double.toString(secondValue),firstValueIndex+1);
} else if (intOrDoubleTest(firstValue) && firstValue == secondValue) { // Special category : indexOf doesn't work since the two vals. are the same --> giving off the same index.
firstValueIndex = str.indexOf(Integer.toString(intValue(firstValue)));
secondValueIndex = str.indexOf(Integer.toString(intValue(secondValue)),firstValueIndex+1);
} else if (intOrDoubleTest(firstValue) && intOrDoubleTest(secondValue)) { // First, sorts out the two vals.
firstValueIndex = str.indexOf(Integer.toString(intValue(firstValue)));
secondValueIndex = str.indexOf(Integer.toString(intValue(secondValue)));
} else if (!intOrDoubleTest(firstValue) && intOrDoubleTest(secondValue)) {
firstValueIndex = str.indexOf(Double.toString(firstValue));
secondValueIndex = str.indexOf(Integer.toString(intValue(secondValue)));
} else if (intOrDoubleTest(firstValue) && !intOrDoubleTest(secondValue)) {
firstValueIndex = str.indexOf(Integer.toString(intValue(firstValue)));
secondValueIndex = str.indexOf(Double.toString(secondValue));
} else if (!intOrDoubleTest(firstValue) && !intOrDoubleTest(secondValue)) {
firstValueIndex = str.indexOf(Double.toString(firstValue));
secondValueIndex = str.indexOf(Double.toString(secondValue));
}
String strToReplace = str.substring(firstValueIndex, secondValueIndex); // Computing the range that need to be replaced.
if (intOrDoubleTest(result)) {
int intResult = intValue(result);
str = str.replace(strToReplace,Integer.toString(intResult));
} else if (!intOrDoubleTest(result)) {
str = str.replace(strToReplace,Double.toString(result));
}
return str;
}
public static boolean intOrDoubleTest(double value) {
return (value % 1 == 0); // True = val is Int, False = val is Double.
}

Answer 1

发现问题：

问题出在strToReplace.substring的strSort方法中。所以很自然地，我以一种更简单、更好的方式重写了整个方法。

public static String strSort(String str, double firstValue, double secondValue, double result) {
//Method that sorts between which vals are ints and which ones are doubles. --> returns them in their current form.
int firstValueIndex;
int secondValueIndex;
if (intOrDoubleTest(firstValue)) {
firstValueIndex = str.indexOf(Integer.toString(intValue(firstValue)));
} else {
firstValueIndex = str.indexOf(Double.toString(firstValue));
}
if (intOrDoubleTest(secondValue)) {
secondValueIndex = str.indexOf(Integer.toString(intValue(secondValue)), firstValueIndex+1);
} else {
secondValueIndex = str.indexOf(Double.toString(secondValue), firstValueIndex+1);
}
int lengthOfSecondVal;
lengthOfSecondVal = (int)(Math.log10(secondValue)+1);
String strToReplace = str.substring(firstValueIndex, secondValueIndex+lengthOfSecondVal); // Computing the range that need to be replaced.
if (intOrDoubleTest(result)) {
int intResult = intValue(result);
str = str.replace(strToReplace,Integer.toString(intResult));
} else if (!intOrDoubleTest(result)) {
str = str.replace(strToReplace,Double.toString(result));
}
return str;
}
public static boolean intOrDoubleTest(double value) {
return (value % 1 == 0); // True = val is Int, False = val is Double.
}

感谢所有帮助过的人！