逆波兰计算器完整版
完整版的逆波兰计算器，功能包括：
（1）支持+，-，*，/，()
（2）支持多位数，支持小数
（3）兼容处理，过滤任何空白字符，包括空格、制表符，换页符
代码实现：
1 import java.util.ArrayList;
2 import java.util.Collections;
3 import java.util.List;
4 import java.util.Stack;
5 import java.util.regex.Pattern;
6
7 public class ReversePolishMultiCalc {
8
9 /**
10 * 匹配 + - * / ( ) 运算符
11 */
12 static final String SYMBOL = "\\+|-|\\*|/|\\(|\\)";
13
14 static final String LEFT = "(";
15 static final String RIGHT = ")";
16 static final String ADD = "+";
17 static final String MINUS= "-";
18 static final String TIMES = "*";
19 static final String DIVISION = "/";
20
21 /**
22 * 加減 + -
23 */
24 static final int LEVEL_01 = 1;
25 /**
26 * 乘除 * /
27 */
28 static final int LEVEL_02 = 2;
29
30 /**
31 * 括号
32 */
33 static final int LEVEL_HIGH = Integer.MAX_VALUE;
34
35
36 static Stack<String> stack = new Stack<>();
37 static List<String> data = Collections.synchronizedList(new ArrayList<String>());
38
39 /**
40 * 去除所有空白符
41 * @param s
42 * @return
43 */
44 public static String replaceAllBlank(String s ){
45 // \\s+ 匹配任何空白字符，包括空格、制表符、换页符等等, 等价于[ \f\n\r\t\v]
46 return s.replaceAll("\\s+","");
47 }
48
49 /**
50 * 判断是不是数字 int double long float
51 * @param s
52 * @return
53 */
54 public static boolean isNumber(String s){
55 Pattern pattern = Pattern.compile("^[-\\+]?[.\\d]*$");
56 return pattern.matcher(s).matches();
57 }
58
59 /**
60 * 判断是不是运算符
61 * @param s
62 * @return
63 */
64 public static boolean isSymbol(String s){
65 return s.matches(SYMBOL);
66 }
67
68 /**
69 * 匹配运算等级
70 * @param s
71 * @return
72 */
73 public static int calcLevel(String s){
74 if("+".equals(s) || "-".equals(s)){
75 return LEVEL_01;
76 } else if("*".equals(s) || "/".equals(s)){
77 return LEVEL_02;
78 }
79 return LEVEL_HIGH;
80 }
81
82 /**
83 * 匹配
84 * @param s
85 * @throws Exception
86 */
87 public static List<String> doMatch (String s) throws Exception{
88 if(s == null || "".equals(s.trim())) throw new RuntimeException("data is empty");
89 if(!isNumber(s.charAt(0)+"")) throw new RuntimeException("data illeagle,start not with a number");
90
91 s = replaceAllBlank(s);
92
93 String each;
94 int start = 0;
95
96 for (int i = 0; i < s.length(); i++) {
97 if(isSymbol(s.charAt(i)+"")){
98 each = s.charAt(i)+"";
99 //栈为空，(操作符，或者 操作符优先级大于栈顶优先级 && 操作符优先级不是( )的优先级 及是 ) 不能直接入栈
100 if(stack.isEmpty() || LEFT.equals(each)
101 || ((calcLevel(each) > calcLevel(stack.peek())) && calcLevel(each) < LEVEL_HIGH)){
102 stack.push(each);
103 }else if( !stack.isEmpty() && calcLevel(each) <= calcLevel(stack.peek())){
104 //栈非空，操作符优先级小于等于栈顶优先级时出栈入列，直到栈为空，或者遇到了(，最后操作符入栈
105 while (!stack.isEmpty() && calcLevel(each) <= calcLevel(stack.peek()) ){
106 if(calcLevel(stack.peek()) == LEVEL_HIGH){
107 break;
108 }
109 data.add(stack.pop());
110 }
111 stack.push(each);
112 }else if(RIGHT.equals(each)){
113 // ) 操作符，依次出栈入列直到空栈或者遇到了第一个)操作符，此时)出栈
114 while (!stack.isEmpty() && LEVEL_HIGH >= calcLevel(stack.peek())){
115 if(LEVEL_HIGH == calcLevel(stack.peek())){
116 stack.pop();
117 break;
118 }
119 data.add(stack.pop());
120 }
121 }
122 start = i ; //前一个运算符的位置
123 }else if( i == s.length()-1 || isSymbol(s.charAt(i+1)+"") ){
124 each = start == 0 ? s.substring(start,i+1) : s.substring(start+1,i+1);
125 if(isNumber(each)) {
126 data.add(each);
127 continue;
128 }
129 throw new RuntimeException("data not match number");
130 }
131 }
132 //如果栈里还有元素，此时元素需要依次出栈入列，可以想象栈里剩下栈顶为/，栈底为+，应该依次出栈入列，可以直接翻转整个stack 添加到队列
133 Collections.reverse(stack);
134 data.addAll(new ArrayList<>(stack));
135
136 System.out.println(data);
137 return data;
138 }
139
140 /**
141 * 算出结果
142 * @param list
143 * @return
144 */
145 public static Double doCalc(List<String> list){
146 Double d = 0d;
147 if(list == null || list.isEmpty()){
148 return null;
149 }
150 if (list.size() == 1){
151 System.out.println(list);
152 d = Double.valueOf(list.get(0));
153 return d;
154 }
155 ArrayList<String> list1 = new ArrayList<>();
156 for (int i = 0; i < list.size(); i++) {
157 list1.add(list.get(i));
158 if(isSymbol(list.get(i))){
159 Double d1 = doTheMath(list.get(i - 2), list.get(i - 1), list.get(i));
160 list1.remove(i);
161 list1.remove(i-1);
162 list1.set(i-2,d1+"");
163 list1.addAll(list.subList(i+1,list.size()));
164 break;
165 }
166 }
167 doCalc(list1);
168 return d;
169 }
170
171 /**
172 * 运算
173 * @param s1
174 * @param s2
175 * @param symbol
176 * @return
177 */
178 public static Double doTheMath(String s1,String s2,String symbol){
179 Double result ;
180 switch (symbol){
181 case ADD : result = Double.valueOf(s1) + Double.valueOf(s2); break;
182 case MINUS : result = Double.valueOf(s1) - Double.valueOf(s2); break;
183 case TIMES : result = Double.valueOf(s1) * Double.valueOf(s2); break;
184 case DIVISION : result = Double.valueOf(s1) / Double.valueOf(s2); break;
185 default : result = null;
186 }
187 return result;
188
189 }
190
191 public static void main(String[] args) {
192 //String math = "9+(3-1)*3+10/2";
193 String math = "12.8 + (2 - 3.55)*4+10/5.0";
194 try {
195 doCalc(doMatch(math));
196 } catch (Exception e) {
197 e.printStackTrace();
198 }
199 }
200
201 }