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What are the regular ways to write whether it is an integer, decimal or real number?
What are the regular ways to write whether it is an integer, decimal or real number?
这次给大家带来判断是否是整数，小数或实数正则有哪些写法，使用判断是否是整数，小数或实数正则的注意事项有哪些，下面就是实战案例，一起来看一下。
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) {
return 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 com.sap.cesp.creditinsight.web.app.util;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class NumberValidationUtils {
private static boolean isMatch(String regex, String orginal){
if (orginal == null || orginal.trim().equals("")) {
return false;
}
Pattern pattern = Pattern.compile(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 com.sap.cesp.creditinsight.web.app.util;
import junit.framework.Assert;
import org.junit.Test;
public class NumberValidationUtilsTest {
/**
* Test method for {@link com.sap.cesp.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 com.sap.cesp.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 com.sap.cesp.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 com.sap.cesp.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 com.sap.cesp.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 com.sap.cesp.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 com.sap.cesp.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"));
}
}相信看了本文案例你已经掌握了方法，更多精彩请关注php中文网其它相关文章！
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