详解Java判断是否是整数，小数或实数的正则表达式
经常会遇到这样的情况，需要判断一个字符串是否是一个合法的数，包括整数，小数或者实数。
网上查到很多文章大多是判断这个字符串是否全为数字，比如下面这段来自StringUtils的代码，可以看到，13.2这样的数字实际上会返回false，可是，他的确是一个数字。
publicstaticbooleanisNumeric(Stringstr){
if(str==null){
returnfalse;
}
intsz=str.length();
for(inti=0;i<sz;i++){
if(Character.isDigit(str.charAt(i))==false){
returnfalse;
}
}
returntrue;
}
当然，网上还能查到很多其他方式，诸如用正则表达式判断是否0-9，用字符ascii码判断是否是数字以及用Double.parseDouble()是否抛出异常来判断是否为数字。
事实上，除了最后一种方式能达到我们的要求，其他的都很难真正做到类似的判断。但是最后一种方式也很难区别出到底是正整数，负整数，正小数还是负小数，而且，捕获异常的方式实在是有些难看。
基于此原因，我自己写了一个工具类，专门用作数的检测，目前能够检测正整数，负整数，整数，正小数，负小数，小数以及实数，采用的仍然是正则表达式的方式，当然，如果有遗漏或者错误，欢迎联系我以便更正，同时也欢迎修改或使用这些代码以便符合你的应用场景。
可以简单讲下正则的思想以便修改，
1.对于正整数而言，可以带+号，第一个数字不能为0
2.对于负整数而言，必须带负号，第一个数字也不能为0
3.对于整数而言，实际是由0，正整数和负整数组成的，所以偷个懒用前两个方法一起判断
4.对于正小数而言，可以考带+号，并考虑两种情况，第一个数字为0和第一个数字不为0，第一个数字为0时，则小数点后面应该不为0，第一个数字不为0时，小数点后可以为任意数字
5.对于负小数而言，必须带负号，其余都同上
6.对于小数，可以带正负号，并且带小数点就行了，但是至少保证小数点有一边不为空，所以这里还是分左边不为空和右边不为空的情况
7.实数比较简单，，要么是整数，要么是小数
packagecom.sap.cesp.creditinsight.web.app.util;
importjava.util.regex.Matcher;
importjava.util.regex.Pattern;
publicclassNumberValidationUtils{
privatestaticbooleanisMatch(Stringregex,Stringorginal){
if(orginal==null||orginal.trim().equals("")){
returnfalse;
}
Patternpattern=Pattern.compile(regex);
MatcherisNum=pattern.matcher(orginal);
returnisNum.matches();
}
publicstaticbooleanisPositiveInteger(Stringorginal){
returnisMatch("^\\+{0,1}[1-9]\\d*",orginal);
}
publicstaticbooleanisNegativeInteger(Stringorginal){
returnisMatch("^-[1-9]\\d*",orginal);
}
publicstaticbooleanisWholeNumber(Stringorginal){
returnisMatch("[+-]{0,1}0",orginal)||isPositiveInteger(orginal)||isNegativeInteger(orginal);
}
publicstaticbooleanisPositiveDecimal(Stringorginal){
returnisMatch("\\+{0,1}[0]\\.[1-9]*|\\+{0,1}[1-9]\\d*\\.\\d*",orginal);
}
publicstaticbooleanisNegativeDecimal(Stringorginal){
returnisMatch("^-[0]\\.[1-9]*|^-[1-9]\\d*\\.\\d*",orginal);
}
publicstaticbooleanisDecimal(Stringorginal){
returnisMatch("[-+]{0,1}\\d+\\.\\d*|[-+]{0,1}\\d*\\.\\d+",orginal);
}
publicstaticbooleanisRealNumber(Stringorginal){
returnisWholeNumber(orginal)||isDecimal(orginal);
}
}
测试用例如下：
packagecom.sap.cesp.creditinsight.web.app.util;
importjunit.framework.Assert;
importorg.junit.Test;
publicclassNumberValidationUtilsTest{
/**
*Testmethodfor{@linkcom.sap.cesp.creditinsight.web.app.util.NumberValidationUtils#isPositiveInteger(java.lang.String)}
*/
//correcttestcase:1,87653521123567
//wrongtestcase:0.1,0,0123,-1,-0.1,ab
@Test
publicvoidtestIsPositiveInteger(){
Assert.assertTrue(NumberValidationUtils.isPositiveInteger("1"));
Assert.assertTrue(NumberValidationUtils.isPositiveInteger("+12"));
Assert.assertTrue(NumberValidationUtils.isPositiveInteger("87653521123567"));
Assert.assertFalse(NumberValidationUtils.isPositiveInteger("0.1"));
Assert.assertFalse(NumberValidationUtils.isPositiveInteger("0"));
Assert.assertFalse(NumberValidationUtils.isPositiveInteger("0123"));
Assert.assertFalse(NumberValidationUtils.isPositiveInteger("-1"));
Assert.assertFalse(NumberValidationUtils.isPositiveInteger("-0.1"));
Assert.assertFalse(NumberValidationUtils.isPositiveInteger("ab"));
}
/**
*Testmethodfor{@linkcom.sap.cesp.creditinsight.web.app.util.NumberValidationUtils#isNegativeInteger(java.lang.String)}
*/
//correcttestcase:-1,-87653521123567
//wrongtestcase:0.1,0,0123,1,-0.1,-ab
@Test
publicvoidtestIsNegativeInteger(){
Assert.assertTrue(NumberValidationUtils.isNegativeInteger("-1"));
Assert.assertTrue(NumberValidationUtils.isNegativeInteger("-87653521123567"));
Assert.assertFalse(NumberValidationUtils.isNegativeInteger("0.1"));
Assert.assertFalse(NumberValidationUtils.isNegativeInteger("0"));
Assert.assertFalse(NumberValidationUtils.isNegativeInteger("0123"));
Assert.assertFalse(NumberValidationUtils.isNegativeInteger("1"));
Assert.assertFalse(NumberValidationUtils.isNegativeInteger("-0.1"));
Assert.assertFalse(NumberValidationUtils.isNegativeInteger("ab"));
}
/**
*Testmethodfor{@linkcom.sap.cesp.creditinsight.web.app.util.NumberValidationUtils#isWholeNumber(java.lang.String)}.
*/
//correcttestcase:-1,0,1,8673434231,-282464334
//wrongtestcase:0.1,0123,-0.1,ab
@Test
publicvoidtestIsWholeNumber(){
Assert.assertTrue(NumberValidationUtils.isWholeNumber("-1"));
Assert.assertTrue(NumberValidationUtils.isWholeNumber("0"));
Assert.assertTrue(NumberValidationUtils.isWholeNumber("1"));
Assert.assertTrue(NumberValidationUtils.isWholeNumber("+12"));
Assert.assertTrue(NumberValidationUtils.isWholeNumber("8673434231"));
Assert.assertTrue(NumberValidationUtils.isWholeNumber("-282464334"));
Assert.assertFalse(NumberValidationUtils.isWholeNumber("0123"));
Assert.assertFalse(NumberValidationUtils.isWholeNumber("0.1"));
Assert.assertFalse(NumberValidationUtils.isWholeNumber("-0.1"));
Assert.assertFalse(NumberValidationUtils.isWholeNumber("ab"));
}
/**
*Testmethodfor{@linkcom.sap.cesp.creditinsight.web.app.util.NumberValidationUtils#isPositiveDecimal(java.lang.String)}
*/
//correcttestcase:0.1,0.132213,1.0
//wrongtestcase:1,0.0,0123,-1,-0.1
@Test
publicvoidtestIsPositiveDecimal(){
Assert.assertTrue(NumberValidationUtils.isPositiveDecimal("0.1"));
Assert.assertTrue(NumberValidationUtils.isPositiveDecimal("0.132213"));
Assert.assertTrue(NumberValidationUtils.isPositiveDecimal("30.00"));
Assert.assertTrue(NumberValidationUtils.isDecimal("0."));
Assert.assertTrue(NumberValidationUtils.isPositiveDecimal("+12.0"));
Assert.assertFalse(NumberValidationUtils.isPositiveDecimal("0123"));
Assert.assertFalse(NumberValidationUtils.isPositiveDecimal("1"));
Assert.assertFalse(NumberValidationUtils.isPositiveDecimal("0.0"));
Assert.assertFalse(NumberValidationUtils.isPositiveDecimal("ab"));
Assert.assertFalse(NumberValidationUtils.isPositiveDecimal("-1"));
Assert.assertFalse(NumberValidationUtils.isPositiveDecimal("-0.1"));
}
/**
*Testmethodfor{@linkcom.sap.cesp.creditinsight.web.app.util.NumberValidationUtils#isNegativeDecimal(java.lang.String)}
*/
//correcttestcase:-0.132213,-1.0
//wrongtestcase:1,0,0123,-1,0.1
@Test
publicvoidtestIsNegativeDecimal(){
Assert.assertTrue(NumberValidationUtils.isNegativeDecimal("-0.132213"));
Assert.assertTrue(NumberValidationUtils.isNegativeDecimal("-1.0"));
Assert.assertTrue(NumberValidationUtils.isDecimal("-0."));
Assert.assertFalse(NumberValidationUtils.isNegativeDecimal("1"));
Assert.assertFalse(NumberValidationUtils.isNegativeDecimal("0"));
Assert.assertFalse(NumberValidationUtils.isNegativeDecimal("0123"));
Assert.assertFalse(NumberValidationUtils.isNegativeDecimal("0.0"));
Assert.assertFalse(NumberValidationUtils.isNegativeDecimal("ab"));
Assert.assertFalse(NumberValidationUtils.isNegativeDecimal("-1"));
Assert.assertFalse(NumberValidationUtils.isNegativeDecimal("0.1"));
}
/**
*Testmethodfor{@linkcom.sap.cesp.creditinsight.web.app.util.NumberValidationUtils#isDecimal(java.lang.String)}.
*/
//correcttestcase:0.1,0.00,-0.132213
//wrongtestcase:1,0,0123,-1,0.,ba
@Test
publicvoidtestIsDecimal(){
Assert.assertTrue(NumberValidationUtils.isDecimal("0.1"));
Assert.assertTrue(NumberValidationUtils.isDecimal("0.00"));
Assert.assertTrue(NumberValidationUtils.isDecimal("+0.0"));
Assert.assertTrue(NumberValidationUtils.isDecimal("-0.132213"));
Assert.assertTrue(NumberValidationUtils.isDecimal("0."));
Assert.assertFalse(NumberValidationUtils.isDecimal("1"));
Assert.assertFalse(NumberValidationUtils.isDecimal("0123"));
Assert.assertFalse(NumberValidationUtils.isDecimal("0"));
Assert.assertFalse(NumberValidationUtils.isDecimal("ab"));
Assert.assertFalse(NumberValidationUtils.isDecimal("-1"));
}
/**
*Testmethodfor{@linkcom.sap.cesp.creditinsight.web.app.util.NumberValidationUtils#isRealNumber(java.lang.String)}.
*/
//correcttestcase:0.032213,-0.234,0.0,1,-1,0
//wrongtestcase:00.13,ab,+0.14
@Test
publicvoidtestIsRealNumber(){
Assert.assertTrue(NumberValidationUtils.isRealNumber("0.032213"));
Assert.assertTrue(NumberValidationUtils.isRealNumber("-0.234"));
Assert.assertTrue(NumberValidationUtils.isRealNumber("0.0"));
Assert.assertTrue(NumberValidationUtils.isRealNumber("1"));
Assert.assertTrue(NumberValidationUtils.isRealNumber("+0.14"));
Assert.assertTrue(NumberValidationUtils.isRealNumber("-1"));
Assert.assertTrue(NumberValidationUtils.isRealNumber("0.0"));
Assert.assertFalse(NumberValidationUtils.isRealNumber("00.13"));
Assert.assertFalse(NumberValidationUtils.isRealNumber("ab"));
}
}
以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持毛票票。