經(jīng)常會(huì)遇到這樣的情況，需要判斷一個(gè)字符串是否是一個(gè)合法的數(shù)，包括整數(shù)，小數(shù)或者實(shí)數(shù)。
網(wǎng)上查到很多文章大多是判斷這個(gè)字符串是否全為數(shù)字，比如下面這段來自StringUtils的代碼，可以看到，13.2這樣的數(shù)字實(shí)際上會(huì)返回false，可是，他的確是一個(gè)數(shù)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; } 當(dāng)然，網(wǎng)上還能查到很多其他方式，諸如用正則表達(dá)式判斷是否0-9，用字符ascii碼判斷是否是數(shù)字以及用Double.parseDouble()是否拋出異常來判斷是否為數(shù)字。
事實(shí)上，除了最后一種方式能達(dá)到我們的要求，其他的都很難真正做到類似的判斷。但是最后一種方式也很難區(qū)別出到底是正整數(shù)，負(fù)整數(shù)，正小數(shù)還是負(fù)小數(shù)，而且，捕獲異常的方式實(shí)在是有些難看。
基于此原因，我自己寫了一個(gè)工具類，專門用作數(shù)的檢測，目前能夠檢測正整數(shù)，負(fù)整數(shù)，整數(shù)，正小數(shù)，負(fù)小數(shù)，小數(shù)以及實(shí)數(shù)，采用的仍然是正則表達(dá)式的方式，當(dāng)然，如果有遺漏或者錯(cuò)誤，歡迎聯(lián)系我以便更正，同時(shí)也歡迎修改或使用這些代碼以便符合你的應(yīng)用場景。
可以簡單講下正則的思想以便修改，
1. 對(duì)于正整數(shù)而言，可以帶+號(hào)，第一個(gè)數(shù)字不能為0
2. 對(duì)于負(fù)整數(shù)而言，必須帶負(fù)號(hào)，第一個(gè)數(shù)字也不能為0
3. 對(duì)于整數(shù)而言，實(shí)際是由0，正整數(shù)和負(fù)整數(shù)組成的，所以偷個(gè)懶用前兩個(gè)方法一起判斷
4. 對(duì)于正小數(shù)而言，可以考帶+號(hào)，并考慮兩種情況，第一個(gè)數(shù)字為0和第一個(gè)數(shù)字不為0，第一個(gè)數(shù)字為0時(shí)，則小數(shù)點(diǎn)后面應(yīng)該不為0，第一個(gè)數(shù)字不為0時(shí)，小數(shù)點(diǎn)后可以為任意數(shù)字
5. 對(duì)于負(fù)小數(shù)而言，必須帶負(fù)號(hào)，其余都同上
6. 對(duì)于小數(shù)，可以帶正負(fù)號(hào)，并且?guī)?shù)點(diǎn)就行了，但是至少保證小數(shù)點(diǎn)有一邊不為空，所以這里還是分左邊不為空和右邊不為空的情況
7. 實(shí)數(shù)比較簡單，，要么是整數(shù)，要么是小數(shù)
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); } } 測試用例如下：
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")); } } 以上就是本文的全部內(nèi)容，希望對(duì)大家的學(xué)習(xí)有所幫助，也希望大家多多支持VEVB武林網(wǎng)。
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