java的StringUtils.isBlank和StringUtils.isEmpty方法区别(org.apache.commons.lang3.StringUtils)

待我称王封你为后i 2022-09-15 05:40 319阅读 0赞

## 前言 ##

估计很多朋友跟我一样，平时也不会特别去注意究竟用`isBlank`还是`isEmpty`去判断空字符串，但是大部分场景优先使用`isBlank`就对了。

*  isEmpty是否为空，只有当`==null`或者`==""`才为空
 *  isBlank是否为真空，`==null`和`==""`以及各种长度的空格`==" "`都为空

而且除了isEmpty/isNotEmpty/isNotBlank/isBlank外,其实还有isAnyEmpty/isNoneEmpty/isAnyBlank/isNoneBlank让我们一起来研究一下`org.apache.commons.lang3.StringUtils`这个工具类吧。

## isBank() ##

是否为真空值(空格或者空值)

- StringUtils.isBlank(null) = true
    - StringUtils.isBlank("") = true
    - StringUtils.isBlank(" ") = true
    - StringUtils.isBlank(" ") = true
    - StringUtils.isBlank("moshow") = false
    - StringUtils.isBlank(" moshow ") = false

/** * <p>Checks if a CharSequence is whitespace, empty ("") or null.</p> * @param cs the CharSequence to check, may be null * @return {@code true} if the CharSequence is null, empty or whitespace * @since 2.0 * @since 3.0 Changed signature from isBlank(String) to isBlank(CharSequence) */
    public static boolean isBlank(final CharSequence cs) { 
        int strLen;
        if (cs == null || (strLen = cs.length()) == 0) { 
            return true;
        }
        for (int i = 0; i < strLen; i++) { 
            if (Character.isWhitespace(cs.charAt(i)) == false) { 
                return false;
            }
        }
        return true;
    }

## StringUtils.isNotBlank() ##

是否真的不为空,不是空格或者空值 ,相当于!isBlank();

public static boolean isNotBlank(final CharSequence cs) { 
            return !isBlank(cs);
        }

## StringUtils.isAnyBlank() ##

是否包含任何真空值(包含空格或空值)

StringUtils.isAnyBlank(null) = true
    StringUtils.isAnyBlank(null, "foo") = true
    StringUtils.isAnyBlank(null, " ") = true
    StringUtils.isAnyBlank("", " ") = true

/** * <p>Checks if any one of the CharSequences are blank ("") or null and not whitespace only..</p> * @param css the CharSequences to check, may be null or empty * @return {@code true} if any of the CharSequences are blank or null or whitespace only * @since 3.2 */
    public static boolean isAnyBlank(final CharSequence... css) { 
      if (ArrayUtils.isEmpty(css)) { 
        return true;
      }
      for (final CharSequence cs : css){ 
        if (isBlank(cs)) { 
          return true;
        }
      }
      return false;
    }

## StringUtils.isNoneBlank() ##

是否没有空值或空格

StringUtils.isNoneBlank(null) = false
    StringUtils.isNoneBlank(null, "foo") = false
    StringUtils.isNoneBlank(null, " ") = false
    StringUtils.isNoneBlank("", " ") = false
    StringUtils.isNoneBlank("moshow", " moshow ") = true

关于其他方法其实都是以此类推，知道这几个，就可以类推对应的is\*Empty等等鞥，这里就不做重复展示。

/** * <p>Checks if none of the CharSequences are blank ("") or null and whitespace only..</p> * @param css the CharSequences to check, may be null or empty * @return {@code true} if none of the CharSequences are blank or null or whitespace only * @since 3.2 */
    public static boolean isNoneBlank(final CharSequence... css) { 
      return !isAnyBlank(css);
    }

## StringUtils的其他方法 ##

官方文档中有提及，这里做一个简单整理和翻译。有些方法确实很好用，但是平时并不会去用。  
[https://commons.apache.org/proper/commons-lang/apidocs/org/apache/commons/lang3/StringUtils.html][https_commons.apache.org_proper_commons-lang_apidocs_org_apache_commons_lang3_StringUtils.html]

<table> 
 <thead> 
  <tr> 
   <th>方法 （整理 by <code>https://zhengkai.blog.csdn.net/</code> ）</th> 
   <th>说明EN</th> 
   <th>说明CN</th> 
  </tr> 
 </thead> 
 <tbody> 
  <tr> 
   <td>IsEmpty/IsBlank</td> 
   <td>checks if a String contains text</td> 
   <td>判断是否包含文本</td> 
  </tr> 
  <tr> 
   <td>Trim/Strip</td> 
   <td>removes leading and trailing whitespace</td> 
   <td>删除多余空格</td> 
  </tr> 
  <tr> 
   <td>Equals/Compare</td> 
   <td>compares two strings in a null</td> 
   <td>safe manner</td> 
  </tr> 
  <tr> 
   <td>startsWith /endsWith</td> 
   <td>check if a String starts/ends with a prefix</td> 
   <td>判断是什么开头/结尾</td> 
  </tr> 
  <tr> 
   <td>IndexOf/LastIndexOf/Contains</td> 
   <td>contain a string and return the index</td> 
   <td>判断字符串在string中的位置，判断是否包含</td> 
  </tr> 
  <tr> 
   <td>IndexOfAny/LastIndexOfAny/IndexOfAnyBut/LastIndexOfAnyBut</td> 
   <td>index of any of a set of Strings</td> 
   <td>如果包含某几个字符串就返回</td> 
  </tr> 
  <tr> 
   <td>ContainsOnly/ContainsNone/ContainsAny</td> 
   <td>checks if String contains only/none/any of these characters</td> 
   <td></td> 
  </tr> 
  <tr> 
   <td>Substring/Left/Right/Mid/SubstringBefore/SubstringAfter/SubstringBetween</td> 
   <td>safe substring extractions</td> 
   <td>截取字符串方法</td> 
  </tr> 
  <tr> 
   <td>Split/Join</td> 
   <td>splits a String into an array of substrings and vice versa</td> 
   <td>切割或者拼接字符串</td> 
  </tr> 
  <tr> 
   <td>Remove/Delete</td> 
   <td>removes part of a String</td> 
   <td>移除</td> 
  </tr> 
  <tr> 
   <td>Replace/Overlay</td> 
   <td>Searches a String and replaces one String with another</td> 
   <td>替换</td> 
  </tr> 
  <tr> 
   <td>Chomp/Chop</td> 
   <td>removes the last part of a String</td> 
   <td>删除字符串的最后一部分</td> 
  </tr> 
  <tr> 
   <td>AppendIfMissing/PrependIfMissing</td> 
   <td>appends a suffix to the start/end of the String if not present</td> 
   <td>前缀后缀</td> 
  </tr> 
  <tr> 
   <td>LeftPad/RightPad/Center/Repeat</td> 
   <td>pads a String</td> 
   <td>填充字符串</td> 
  </tr> 
  <tr> 
   <td>UpperCase/LowerCase/SwapCase/Capitalize/Uncapitalize</td> 
   <td>changes the case of a String</td> 
   <td>大写/小写/交换大小写/大写/取消大写</td> 
  </tr> 
  <tr> 
   <td>CountMatches</td> 
   <td>counts the number of occurrences of one String in another</td> 
   <td>统计匹配</td> 
  </tr> 
  <tr> 
   <td>IsAlpha/IsNumeric/IsWhitespace/IsAsciiPrintable</td> 
   <td>checks the characters in a String</td> 
   <td>是否字母/数字/空格/Ascii</td> 
  </tr> 
  <tr> 
   <td>DefaultString</td> 
   <td>protects against a null input String</td> 
   <td>防止空输入字符串</td> 
  </tr> 
  <tr> 
   <td>Rotate</td> 
   <td>rotate (circular shift) a String</td> 
   <td>旋转（循环移位）一个字符串</td> 
  </tr> 
  <tr> 
   <td>Reverse/ReverseDelimited</td> 
   <td>reverses a String</td> 
   <td>反转字符串</td> 
  </tr> 
  <tr> 
   <td>Abbreviate</td> 
   <td>abbreviates a string using ellipses or another given String</td> 
   <td>使用省略号或另一个给定的字符串缩写字符串</td> 
  </tr> 
  <tr> 
   <td>Difference</td> 
   <td>compares Strings and reports on their differences</td> 
   <td>比较字符串并报告它们的差异</td> 
  </tr> 
  <tr> 
   <td>LevenshteinDistance</td> 
   <td>the number of changes needed to change one String into another</td> 
   <td>将一个字符串更改为另一个字符串所需的更改次数</td> 
  </tr> 
 </tbody> 
</table>

[https_commons.apache.org_proper_commons-lang_apidocs_org_apache_commons_lang3_StringUtils.html]: https://commons.apache.org/proper/commons-lang/apidocs/org/apache/commons/lang3/StringUtils.html