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