完整逆波兰计算器（Java）
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功能
支持 + - * / ( )
多位数，支持小数,
兼容处理, 过滤任何空白字符，包括空格、制表符、换页符
基本思路
中缀表达式转后缀表达式
代码
package stack;import java.util.ArrayList;import java.util.List;import java.util.Stack;import java.util.Collections;import java.util.regex.Pattern;public class ReversePolishMultiCalc { //匹配运算符 static final String SYMBOL = "\\+|-|\\*|/|\\(|\\)"; static final String LEFT = "("; static final String RIGHT = ")"; static final String ADD = "+"; static final String MINUS = "-"; static final String TIMES = "*"; static final String DIVISION = "/"; //优先级 static final int LEVEL_01 = 1; static final int LEVEL_02 = 2; static final int LEVEL_HIGH = Integer.MAX_VALUE; static Stack<String> stack = new Stack<>(); static List<String> data = Collections.synchronizedList(new ArrayList<String>()); //去除所有空白符号 public static String replaceAllBlank(String s) { return s.replaceAll("\\s+", ""); } //判断是否为数字 public static boolean isNumber(String s) { Pattern pattern = Pattern.compile("^[-\\+]?[.\\d]*$"); return pattern.matcher(s).matches(); } //判断是否是运算符 public static boolean isSymbol(String s) { return s.matches(SYMBOL); } //匹配运算优先级 public static int calcLevel(String s) { if ("+".equals(s) || "-".equals(s)) { return LEVEL_01; } else if ("*".equals(s) || "/".equals(s)) { return LEVEL_02; } return LEVEL_HIGH; } //匹配 public static List<String> doMatch(String s) throws Exception { if (s == null || "".equals(s.trim())) throw new RuntimeException("data is empty"); if (!isNumber(s.charAt(0) + "")) throw new RuntimeException("data illeagle,start not with a number"); s = replaceAllBlank(s); String each; int start = 0; for (int i = 0; i < s.length(); i++) { if (isSymbol(s.charAt(i) + "")) { each = s.charAt(i) + ""; if (stack.isEmpty() || LEFT.equals(each) || ((calcLevel(each) > calcLevel(stack.peek())) && calcLevel(each) < LEVEL_HIGH)) { stack.push(each); } else if (!stack.isEmpty() && calcLevel(each) <= calcLevel(stack.peek())) { while (!stack.isEmpty() && calcLevel(each) <= calcLevel(stack.peek())) { if (calcLevel(stack.peek()) == LEVEL_HIGH) { break; } data.add(stack.pop()); } stack.push(each); } else if (RIGHT.equals(each)) { while (!stack.isEmpty() && LEVEL_HIGH >= calcLevel(stack.peek())) { if (LEVEL_HIGH == calcLevel(stack.peek())) { stack.pop(); break; } data.add(stack.pop()); } } start = i; } else if (i == s.length() - 1 || isSymbol(s.charAt(i + 1) + "")) { each = start == 0 ? s.substring(start, i + 1) : s.substring(start + 1, i + 1); if (isNumber(each)) { data.add(each); continue; } throw new RuntimeException("data not match number"); } } Collections.reverse(stack); data.addAll(new ArrayList<>(stack)); System.out.println(data); return data; } //计算结果 public static Double doCalc(List<String> list){ Double d = 0d; if(list == null || list.isEmpty()){ return null; } if(list.size() == 1){ System.out.println(list); d = Double.valueOf(list.get(0)); return d; } ArrayList<String> list1 = new ArrayList<>(); for (int i = 0; i < list.size(); i++) { list1.add(list.get(i)); if(isSymbol(list.get(i))){ Double d1 = doTheMath(list.get(i-2),list.get(i-1),list.get(i)); list1.remove(i); list1.remove(i-1); list1.set(i-2,d1+""); list1.addAll(list.subList(i+1,list.size())); break; } } doCalc(list1); return d; } //运算 public static Double doTheMath(String s1,String s2,String symbol){ Double result; switch (symbol){ case ADD: result = Double.valueOf(s1) + Double.valueOf(s2); break; case MINUS: result = Double.valueOf(s1) - Double.valueOf(s2); break; case TIMES: result = Double.valueOf(s1) * Double.valueOf(s2); break; case DIVISION: result = Double.valueOf(s1) / Double.valueOf(s2); break; default: result = null; } return result; } public static void main(String[] args) { String math = "12.8 + (2-3.55)*4+10/5.0"; try{ doCalc(doMatch(math)); }catch (Exception e){ e.printStackTrace(); } }}结果
感谢
尚硅谷万能的网络
以及勤劳的自己