Mega Code Archive
Checks whether the String a valid Java number
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/*
* @(#)$Id: StringUtils.java 3619 2008-03-26 07:23:03Z yui $
*
* Copyright 2006-2008 Makoto YUI
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
* Contributors:
* Makoto YUI - initial implementation
*/
//package xbird.util.string;
/**
*
* <DIV lang="en"></DIV>
* <DIV lang="ja"></DIV>
*
* @author Makoto YUI (yuin405+xbird@gmail.com)
*/
public final class StringUtils {
/**
* Checks whether the String a valid Java number.
* this code is ported from jakarta commons lang.
*
* @link http://jakarta.apache.org/commons/lang/apidocs/org/apache/commons/lang/math/NumberUtils.html
*/
public static boolean isNumber(String str) {
if(str == null || str.length() == 0) {
return false;
}
char[] chars = str.toCharArray();
int sz = chars.length;
boolean hasExp = false;
boolean hasDecPoint = false;
boolean allowSigns = false;
boolean foundDigit = false;
// deal with any possible sign up front
int start = (chars[0] == '-') ? 1 : 0;
if(sz > start + 1) {
if(chars[start] == '0' && chars[start + 1] == 'x') {
int i = start + 2;
if(i == sz) {
return false; // str == "0x"
}
// checking hex (it can't be anything else)
for(; i < chars.length; i++) {
if((chars[i] < '0' || chars[i] > '9') && (chars[i] < 'a' || chars[i] > 'f')
&& (chars[i] < 'A' || chars[i] > 'F')) {
return false;
}
}
return true;
}
}
sz--; // don't want to loop to the last char, check it afterwords
// for type qualifiers
int i = start;
// loop to the next to last char or to the last char if we need another digit to
// make a valid number (e.g. chars[0..5] = "1234E")
while(i < sz || (i < sz + 1 && allowSigns && !foundDigit)) {
if(chars[i] >= '0' && chars[i] <= '9') {
foundDigit = true;
allowSigns = false;
} else if(chars[i] == '.') {
if(hasDecPoint || hasExp) {
// two decimal points or dec in exponent
return false;
}
hasDecPoint = true;
} else if(chars[i] == 'e' || chars[i] == 'E') {
// we've already taken care of hex.
if(hasExp) {
// two E's
return false;
}
if(!foundDigit) {
return false;
}
hasExp = true;
allowSigns = true;
} else if(chars[i] == '+' || chars[i] == '-') {
if(!allowSigns) {
return false;
}
allowSigns = false;
foundDigit = false; // we need a digit after the E
} else {
return false;
}
i++;
}
if(i < chars.length) {
if(chars[i] >= '0' && chars[i] <= '9') {
// no type qualifier, OK
return true;
}
if(chars[i] == 'e' || chars[i] == 'E') {
// can't have an E at the last byte
return false;
}
if(!allowSigns
&& (chars[i] == 'd' || chars[i] == 'D' || chars[i] == 'f' || chars[i] == 'F')) {
return foundDigit;
}
if(chars[i] == 'l' || chars[i] == 'L') {
// not allowing L with an exponent
return foundDigit && !hasExp;
}
// last character is illegal
return false;
}
// allowSigns is true iff the val ends in 'E'
// found digit it to make sure weird stuff like '.' and '1E-' doesn't pass
return !allowSigns && foundDigit;
}
}
]]>