正则表达式&自定义异常 典型案例

时间:2024-01-11 12:11:08
import java.util.regex.Matcher;
import java.util.regex.Pattern; public class Test
{ public static void main(String[] args)
{
System.out.println(oper(" 12.3+213.1")); } public static float oper(String s)
{
Float res = null;
Pattern p = Pattern
.compile("\\s*(\\d+)(\\.*)(\\d+)\\s*(\\+|-|\\*\\/)\\s*(\\d+)(\\.*)(\\d+)\\s*");
Matcher m = p.matcher(s); boolean b = m.matches();
if (!b)
{
throw new couldNotCaculateException("匹配错误");
} String s1 = m.group(1) + m.group(2) + m.group(3);
String s2 = m.group(5) + m.group(6) + m.group(7); Float f1 = Float.parseFloat(s1);
Float f2 = Float.parseFloat(s2);
if ("+".equals(m.group(4)))
{
res = f1 + f2;
} else if ("-".equals(m.group(4)))
{
res = f1 - f2;
} else if ("*".equals(m.group(4)))
{
res = f1 * f2;
} else if ("/".equals(m.group(4)))
{
if (f2 == 0)
{
throw new couldNotCaculateException("除数不能为o");
}
res = f1 / f2;
} return res;
} } class couldNotCaculateException extends RuntimeException
{ private static final long serialVersionUID = -1127307315212919888L; public couldNotCaculateException(String msg)
{
super(msg);
}
}