isfloat.java

模拟图书馆管理系统 实现了各种图书馆管理功能

import java.lang.*;
import java.util.regex.*;
public class IsFloat {
 public static boolean isFloat(String arg){
	 final String Digits     = "(\\p{Digit}+)";
	 final String HexDigits  = "(\\p{XDigit}+)";
	 final String Exp        = "[eE][+-]?"+Digits;
	 final String fpRegex    =
	            ("[\\x00-\\x20]*"+// Optional leading "whitespace"
	             "[+-]?(" +       // Optional sign character
	             "NaN|" +         // "NaN" string
	             "Infinity|" +    // "Infinity" string
	             "((("+Digits+"(\\.)?("+Digits+"?)("+Exp+")?)|"+

	             "(\\.("+Digits+")("+Exp+")?)|"+

	       "((" +
	        "(0[xX]" + HexDigits + "(\\.)?)|" +
	        "(0[xX]" + HexDigits + "?(\\.)" + HexDigits + ")" +

	        ")[pP][+-]?" + Digits + "))" +
	             "[fFdD]?))" +
	             "[\\x00-\\x20]*");
	 
	 if (Pattern.matches(fpRegex,arg)){
        //System.out.println(Double.valueOf(arg));
		 return true;
	 }
    else {
    	return false;
        //System.out.println("wrong");
    }
	 
 }
}