double res = cal(nowValue, parts.get(pos), parts.get(pos+1)); return calPostFixParts(parts, pos+2, res); } protected static double cal(double m, String b, String operator) { if(operator.length()!=1) throw new RuntimeException("操作符不合法");
Character op = operator.charAt(0); double n = Double.valueOf(b); switch(op) { case '+':return m+n; case '-':return m-n; case '*':return m*n; case '/':return m/n; case '^':return Math.pow(m, n); default:throw new RuntimeException("操作符不合法"); } }}
import java.util.List;
public class PostFix {
public static void main(String[] args) {
StringBuilder sb = new StringBuilder();
for(int i=0;i<args.length;i++)
sb.append(args[i]+" ");
System.out.println(calPostFix(sb.toString())); }
private static double calPostFix(String str)
{
List<String> parts = new LinkedList<String>();
for(int i=0;i<str.length();)
{
if(str.charAt(i)==' ')
{
i++;
continue;
}
int pos = i;
while(Character.isDigit(str.charAt(i)) || str.charAt(i)=='.') //数字
i++;
if(pos!=i)
{
parts.add(str.substring(pos, i));
continue;
}
//操作符
parts.add(str.charAt(i++)+"");
}
double nowValue = Double.parseDouble(parts.get(0));
return calPostFixParts(parts, 1, nowValue);
}
/**这里递归调用**/
private static double calPostFixParts(List<String> parts, int pos, double nowValue)
{
if(pos>=parts.size())
return nowValue;
double res = cal(nowValue, parts.get(pos), parts.get(pos+1));
return calPostFixParts(parts, pos+2, res);
} protected static double cal(double m, String b, String operator)
{
if(operator.length()!=1)
throw new RuntimeException("操作符不合法");
Character op = operator.charAt(0);
double n = Double.valueOf(b);
switch(op)
{
case '+':return m+n;
case '-':return m-n;
case '*':return m*n;
case '/':return m/n;
case '^':return Math.pow(m, n);
default:throw new RuntimeException("操作符不合法");
}
}}