Java判斷是否是整數,小數或實數的正則表示式
阿新 • • 發佈:2019-01-24
經常會遇到這樣的情況,需要判斷一個字串是否是一個合法的數,包括整數,小數或者實數。
網上查到很多文章大多是判斷這個字串是否全為數字,比如下面這段來自StringUtils的程式碼,可以看到,13.2這樣的數字實際上會返回false,可是,他的確是一個數字。
- publicstaticboolean isNumeric(String str) {
- if (str == null) {
- returnfalse;
- }
- int sz = str.length();
-
for (int
- if (Character.isDigit(str.charAt(i)) == false) {
- returnfalse;
- }
- }
- returntrue;
- }
事實上,除了最後一種方式能達到我們的要求,其他的都很難真正做到類似的判斷。但是最後一種方式也很難區別出到底是正整數,負整數,正小數還是負小數,而且,捕獲異常的方式實在是有些難看。
基於此原因,我自己寫了一個工具類,專門用作數的檢測,目前能夠檢測正整數,負整數,整數,正小數,負小數,小數以及實數,採用的仍然是正則表示式的方式,當然,如果有遺漏或者錯誤,歡迎聯絡我以便更正,同時也歡迎修改或使用這些程式碼以便符合你的應用場景。
可以簡單講下正則的思想以便修改,
1. 對於正整數而言,可以帶+號,第一個數字不能為0
2. 對於負整數而言,必須帶負號,第一個數字也不能為0
3. 對於整數而言,實際是由0,正整數和負整陣列成的,所以偷個懶用前兩個方法一起判斷
4. 對於正小數而言,可以考帶+號,並考慮兩種情況,第一個數字為0和第一個數字不為0,第一個數字為0時,則小數點後面應該不為0,第一個數字不為0時,小數點後可以為任意數字
5. 對於負小數而言,必須帶負號,其餘都同上
6. 對於小數,可以帶正負號,並且帶小數點就行了,但是至少保證小數點有一邊不為空,所以這裡還是分左邊不為空和右邊不為空的情況
7. 實數比較簡單,,要麼是整數,要麼是小數
- package com.sap.cesp.creditinsight.web.app.util;
- import java.util.regex.Matcher;
- import java.util.regex.Pattern;
- publicclass NumberValidationUtils {
- privatestaticboolean isMatch(String regex, String orginal){
- if (orginal == null || orginal.trim().equals("")) {
- returnfalse;
- }
- Pattern pattern = Pattern.compile(regex);
- Matcher isNum = pattern.matcher(orginal);
- return isNum.matches();
- }
- publicstaticboolean isPositiveInteger(String orginal) {
- return isMatch("^\\+{0,1}[1-9]\\d*", orginal);
- }
- publicstaticboolean isNegativeInteger(String orginal) {
- return isMatch("^-[1-9]\\d*", orginal);
- }
- publicstaticboolean isWholeNumber(String orginal) {
- return isMatch("[+-]{0,1}0", orginal) || isPositiveInteger(orginal) || isNegativeInteger(orginal);
- }
- publicstaticboolean isPositiveDecimal(String orginal){
- return isMatch("\\+{0,1}[0]\\.[1-9]*|\\+{0,1}[1-9]\\d*\\.\\d*", orginal);
- }
- publicstaticboolean isNegativeDecimal(String orginal){
- return isMatch("^-[0]\\.[1-9]*|^-[1-9]\\d*\\.\\d*", orginal);
- }
- publicstaticboolean isDecimal(String orginal){
- return isMatch("[-+]{0,1}\\d+\\.\\d*|[-+]{0,1}\\d*\\.\\d+", orginal);
- }
- publicstaticboolean isRealNumber(String orginal){
- return isWholeNumber(orginal) || isDecimal(orginal);
- }
- }
- package com.sap.cesp.creditinsight.web.app.util;
- import junit.framework.Assert;
- import org.junit.Test;
- publicclass 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
- publicvoid 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
- publicvoid 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
- publicvoid 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
- publicvoid 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
- publicvoid testIsNegativeDecimal() {
- Assert.assertTrue(NumberValidationUtils.isNegativeDecimal("-0.132213"));
- Assert.assertTrue(NumberValidationUtils.isNegativeDecimal("-1.0"));
- Assert.assertTrue(NumberValidationUtils.isDecimal("-0."));
- Assert.assertFalse(NumberValidationUtils.isNegativeDecimal("1"));