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详解Java判断整数、小数或实数的正则表达式

2016-12-13??来源:blog.csdn.net??我有话说??收藏本文

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")); 
     
  } 
 
} 

本文结束,欢迎阅读。

原文链接:http://blog.csdn.net/z69183787/article/details/12848685

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