字符串运算java简单实现，没有优化，没有大批量的测试。

import java.util.ArrayList;import java.util.List;public class MathString {public static void main(String[] args){String press = "12*12.22-7*(23.45-(-2))+(12-34)";press = press.replaceAll("[\\[\\{]", "(").replaceAll("[\\]\\}]", ")");System.out.println(parseString(press));}public static String parseString(String press){int lasc = press.lastIndexOf("(");if(lasc==-1){return String.valueOf(addString(press));}String firstKHString = press.substring(0,lasc);String lastFKHString = press.substring(lasc+1);//System.out.println("firstKHString---"+firstKHString);//System.out.println("lastFKHString---"+lastFKHString);int firc = lastFKHString.indexOf(")");lastFKHString = press.substring(firc+lasc+2);//System.out.println("lastFKHString---"+lastFKHString);String currentPress = press.substring(lasc+1,firc+lasc+1);//System.out.println(currentPress);return parseString(firstKHString+addString(currentPress)+lastFKHString);}public static double addString(String press){//System.out.println(press);press = repAddString(press);press = repString(press);//System.out.println(press);String[] numbers = press.split("[\\+]");double number = 0;List<String> fhs = getFHAdd(press);for(int i=0 ; i<numbers.length; i++ ){String curNum = numbers[i];//System.out.println(curNum);if(curNum.equals("")){curNum="0";}if(fhs.get(i).equals("+")){number = number + mathString(curNum);}else if(fhs.get(i).equals("-")){number = number - mathString(curNum);}}return number;}public static double mathString(String press){  /*int firstCH = press.indexOf("*");int firstC = press.indexOf("/");if(firstCH == -1 && firstC == -1){return Double.parseDouble(press);}int firstindex = firstC < firstCH ? firstC : firstCH;   */press = repAddString(press);String[] numbers = press.split("[\\*\\/]");List<String> fhs = getFH(press);double result = 1;for(int i=0 ; i<numbers.length; i++){if(fhs.get(i).equals("*")){result = result * Double.parseDouble(numbers[i]);}else if(fhs.get(i).equals("/")){if(Double.parseDouble(numbers[i])==0){throw new ArithmeticException("表达式中被除数有空值！");}result = result / Double.parseDouble(numbers[i]);}}return result;}public static String repAddString(String press){return press.replace("++", "+").replace("--", "+").replace("+-", "-").replace("-+", "-");}public static String repString(String press){StringBuffer sb = new StringBuffer();char ch = 0;for(char c:press.toCharArray()){if(c=='-'&&'/'!=ch&&'*'!=ch){sb.append("+");}ch = c;sb.append(c);}return sb.toString();}public static List<String> getFH(String press){char[] chars = press.toCharArray();List<String> fhs = new ArrayList<String>();fhs.add("*");for(char c : chars){if(c=='*' || c=='/'){fhs.add(String.valueOf(c));}}return fhs;}public static List<String> getFHAdd(String press){char[] chars = press.toCharArray();List<String> fhs = new ArrayList<String>();fhs.add("+");for(char c : chars){if(c=='+'){fhs.add(String.valueOf(c));}}return fhs;}}