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。
public static boolean isNumeric(String str) {
if (str == null) {
时间正则表达式javareturn false;
}
int sz = str.length();
for (int i = 0; i < sz; i++) {
if (Character.isDigit(str.charAt(i)) == false) {
return false;
}
}
return true;
}
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
package sp.creditinsight.web.app.util;
import Matcher;
import Pattern;
public class NumberValidationUtils {
private static boolean isMatch(String regex, String orginal){
if (orginal == null || im().equals("")) {
return false;
}
Pattern pattern = Patternpile(regex);
Matcher isNum = pattern.matcher(orginal);
return isNum.matches();
}
public static boolean isPositiveInteger(String orginal) {
return isMatch("^\\+{0,1}[1-9]\\d*", orginal);
}
public static boolean isNegativeInteger(String orginal) {
return isMatch("^-[1-9]\\d*", orginal);
}
public static boolean isWholeNumber(String orginal) {
return isMatch("[+-]{0,1}0", orginal) || isPositiveInteger(orginal) || isNegativeInteger(orginal);
}
public static boolean isPositiveDecimal(String orginal){
return isMatch("\\+{0,1}[0]\\.[1-9]*|\\+{0,1}[1-9]\\d*\\.\\d*", orginal);
}
public static boolean isNegativeDecimal(String orginal){
return isMatch("^-[0]\\.[1-9]*|^-[1-9]\\d*\\.\\d*", orginal);
}
public static boolean isDecimal(String orginal){
return isMatch("[-+]{0,1}\\d+\\.\\d*|[-+]{0,1}\\d*\\.\\d+", orginal);
}
public static boolean isRealNumber(String orginal){
return isWholeNumber(orginal) || isDecimal(orginal);
}
}
测试⽤例如下：
package sp.creditinsight.web.app.util;
import junit.framework.Assert;
import org.junit.Test;
public class NumberValidationUtilsTest {
/**
* Test method for {@link sp.creditinsight.web.app.util.NumberValidationUtils#isPositiveInteger(java.lang.String)}    */
//correct test case: 1, 87653521123567
//wrong test case: 0.1, 0, 0123, -1, -0.1, ab
@Test
public void testIsPositiveInteger() {
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"));
}
/**
* Test method for {@link sp.creditinsight.web.app.util.NumberValidationUtils#isNegativeInteger(java.lang.String)}    */
//correct test case: -1, -87653521123567
//wrong test case: 0.1, 0, 0123, 1, -0.1, -ab
@Test
public void testIsNegativeInteger() {
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"));
}
/**
* Test method for {@link sp.creditinsight.web.app.util.NumberValidationUtils#isWholeNumber(java.lang.String)}.    */
//correct test case: -1, 0, 1, 8673434231, -282464334
//wrong test case: 0.1, 0123, -0.1, ab
@Test
public void testIsWholeNumber() {
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"));
}
/
**
* Test method for {@link sp.creditinsight.web.app.util.NumberValidationUtils#isPositiveDecimal(java.lang.String)}    */
//correct test case: 0.1, 0.132213, 1.0
//wrong test case: 1, 0.0, 0123, -1, -0.1
@Test
public void testIsPositiveDecimal() {
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"));
}
/**
* Test method for {@link sp.creditinsight.web.app.util.NumberValidationUtils#isNegativeDecimal(java.lang.String)}    */
//correct test case: -0.132213, -1.0
//wrong test case: 1, 0, 0123, -1, 0.1
@Test
public void testIsNegativeDecimal() {
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"));
}
/**
* Test method for {@link sp.creditinsight.web.app.util.NumberValidationUtils#isDecimal(java.lang.String)}.
*/
//correct test case: 0.1, 0.00, -0.132213
//wrong test case: 1, 0, 0123, -1, 0., ba
@Test
public void testIsDecimal() {
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"));
}
/
**
* Test method for {@link sp.creditinsight.web.app.util.NumberValidationUtils#isRealNumber(java.lang.String)}.
*/
//correct test case: 0.032213, -0.234, 0.0, 1, -1, 0
//wrong test case: 00.13, ab, +0.14
@Test
public void testIsRealNumber() {
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。

版权声明：本站内容均来自互联网，仅供演示用，请勿用于商业和其他非法用途。如果侵犯了您的权益请与我们联系QQ:729038198，我们将在24小时内删除。