我在启动 UI 时遇到错误，导致此代码在标题中向我吐出错误。它适用于我的所有其他运算符符号，所以我真的不确定这里发生了什么。我不想发布所有代码，所以如果这还不够，您可以在我的 gitHub 上找到其余代码:https://github.com/jparr721/Calculator-App/tree/master/src/calculator
public class Calculation_Controls {
public double A, B;
private String[] operators = new String[] {"-","+","/","*","x","^","X"};
/**
* Check for the symbol being used within the TextArea to then
* apply the correct caculation method.
* FIXME - Allow for multiple symbols to be used and have them return
* FIXME - a result in accordance with PEMDAS
*
*@param nums
*
* @return operator, or error
*/
public String findSymbol(String nums) {
for (String operator : operators) {
if (nums.contains(operator)) {
return operator;
}
}
return "invalid input";
}
/**
* Input method to take the user input from the text area
* and apply the correct calculation to it
*
* @param nums - Stores the input as a String which I then convert to an int
* then back to a string to be printed to the TextArea
*
* @return - The result of the calculation as a string
*/
public String input(String nums){
String operator = findSymbol(nums);
if (operator == null){
System.out.println("Invalid input");
}
String[] split = nums.split(operator);
int left = Integer.parseInt(split[0]);
int right = Integer.parseInt((split[1]));
String result = "";
switch (operator){
case "+":
result = Double.toString(add(left, right));
break;
case "-":
result = Double.toString(subtract(left, right));
break;
case "*":
case "x":
case "X":
result = Double.toString(multiply(left, right));
break;
case "/":
result = Double.toString(divide(left, right));
break;
case "^":
result = Double.toString(pwr(left, right));
break;
default:
System.out.println("Invalid Operator");
}
return result;
}
最佳答案
正则表达式中有保留字符，您应该对这些字符进行转义以实现您想要的效果。例如，你不能使用String.split("+")，你必须使用String.split("\\+")。
正确的运算符是:
String[] operators = new String[] {"-","\\+","/","\\*","x","\\^","X"};
关于java.util.regex.PatternSyntaxException : Dangling meta character '+' near index 0 +，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/40246231/