探索StringUtils3之StringUtils.isEmpty()和StringUtils.isBlank()的區別

也許你兩個都不知道,也許你除了isEmpty/isNotEmpty/isNotBlank/isBlank外,並不知道還有isAnyEmpty/isNoneEmpty/isAnyBlank/isNoneBlank的存在, come on ,讓我們一起來探索org.apache.commons.lang3.StringUtils;這個工具類.

#isEmpty系列

StringUtils.isEmpty()

>>>是否為空. 可以看到 " " 空格是會繞過這種空判斷,因為是一個空格,並不是嚴格的空值,會導致 isEmpty(" ")=false

• StringUtils.isEmpty(null) = true
• StringUtils.isEmpty("") = true
• StringUtils.isEmpty(" ") = false
• StringUtils.isEmpty(“bob”) = false
• StringUtils.isEmpty(" bob ") = false

    /**
     *
     * <p>NOTE: This method changed in Lang version 2.0.
     * It no longer trims the CharSequence.
     * That functionality is available in isBlank().</p>
     *
     * @param cs  the CharSequence to check, may be null
     * @return {@code true} if the CharSequence is empty or null
     * @since 3.0 Changed signature from isEmpty(String) to isEmpty(CharSequence)
     */
    public static boolean isEmpty(final CharSequence cs) {
        return cs == null || cs.length() == 0;
    }

StringUtils.isNotEmpty()

>>>相當於不為空 , = !isEmpty()

public static boolean isNotEmpty(final CharSequence cs) {
        return !isEmpty(cs);
    }

StringUtils.isAnyEmpty()

>>>是否有一個為空,只有一個為空,就為true.

• StringUtils.isAnyEmpty(null) = true
• StringUtils.isAnyEmpty(null, “foo”) = true
• StringUtils.isAnyEmpty("", “bar”) = true
• StringUtils.isAnyEmpty(“bob”, “”) = true
• StringUtils.isAnyEmpty(" bob ", null) = true
• StringUtils.isAnyEmpty(" ", “bar”) = false
• StringUtils.isAnyEmpty(“foo”, “bar”) = false

	/**
     * @param css  the CharSequences to check, may be null or empty
     * @return {@code true} if any of the CharSequences are empty or null
     * @since 3.2
     */
    public static boolean isAnyEmpty(final CharSequence... css) {
      if (ArrayUtils.isEmpty(css)) {
        return true;
      }
      for (final CharSequence cs : css){
        if (isEmpty(cs)) {
          return true;
        }
      }
      return false;
    }

StringUtils.isNoneEmpty()

>>>相當於!isAnyEmpty(css) , 必須所有的值都不為空才返回true

    /**
     * <p>Checks if none of the CharSequences are empty ("") or null.</p>
     *
     * <pre>
     * StringUtils.isNoneEmpty(null)             = false
     * StringUtils.isNoneEmpty(null, "foo")      = false
     * StringUtils.isNoneEmpty("", "bar")        = false
     * StringUtils.isNoneEmpty("bob", "")        = false
     * StringUtils.isNoneEmpty("  bob  ", null)  = false
     * StringUtils.isNoneEmpty(" ", "bar")       = true
     * StringUtils.isNoneEmpty("foo", "bar")     = true
     * </pre>
     *
     * @param css  the CharSequences to check, may be null or empty
     * @return {@code true} if none of the CharSequences are empty or null
     * @since 3.2
     */
    public static boolean isNoneEmpty(final CharSequence... css) {
      return !isAnyEmpty(css);
    }    

#isBank系列

StringUtils.isBlank()

>>> 是否為真空值(空格或者空值)

• StringUtils.isBlank(null) = true
• StringUtils.isBlank("") = true
• StringUtils.isBlank(" ") = true
• StringUtils.isBlank(“bob”) = false
• StringUtils.isBlank(" bob ") = 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()

>>> 是否真的不為空,不是空格或者空值 ,相當於!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, null) = true
• StringUtils.isAnyBlank("", “bar”) = true
• StringUtils.isAnyBlank(“bob”, “”) = true
• StringUtils.isAnyBlank(" bob ", null) = true
• StringUtils.isAnyBlank(" ", “bar”) = true
• StringUtils.isAnyBlank(“foo”, “bar”) = false

     /**
     * <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()

>>>是否全部都不包含空值或空格

• StringUtils.isNoneBlank(null) = false
• StringUtils.isNoneBlank(null, “foo”) = false
• StringUtils.isNoneBlank(null, null) = false
• StringUtils.isNoneBlank("", “bar”) = false
• StringUtils.isNoneBlank(“bob”, “”) = false
• StringUtils.isNoneBlank(" bob ", null) = false
• StringUtils.isNoneBlank(" ", “bar”) = false
• StringUtils.isNoneBlank(“foo”, “bar”) = true

    /**
     * <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

可以參考官方的文件,裡面有詳細的描述,有些方法還是很好用的.
https://commons.apache.org/proper/commons-lang/apidocs/org/apache/commons/lang3/StringUtils.html
.

方法名	英文解釋	中文解釋
IsEmpty/IsBlank	checks if a String contains text	檢查字串是否包含文字
Trim/Strip	removes leading and trailing whitespace	刪除前導和尾隨空格
Equals/Compare	compares two strings null-safe	比較兩個字串是否為null安全的
startsWith	check if a String starts with a prefix null-safe	檢查字串是否以字首null安全開頭
endsWith	check if a String ends with a suffix null-safe	檢查字串是否以字尾null安全結尾
IndexOf/LastIndexOf/Contains	null-safe index-of checks	包含空安全索引檢查
IndexOfAny/LastIndexOfAny/IndexOfAnyBut/LastIndexOfAnyBut	index-of any of a set of Strings	任意一組字串的索引
ContainsOnly/ContainsNone/ContainsAny	does String contains only/none/any of these characters	字串是否僅包含/無/這些字元中的任何一個
Substring/Left/Right/Mid	null-safe substring extractions	字串安全提取
SubstringBefore/SubstringAfter/SubstringBetween	substring extraction relative to other strings -相對其他字串的字串提取
Split/Join	splits a String into an array of substrings and vice versa	將字串拆分為子字串陣列，反之亦然
Remove/Delete	removes part of a String -刪除字串的一部分
Replace/Overlay	Searches a String and replaces one String with another	搜尋字串，然後用另一個字串替換
Chomp/Chop	removes the last part of a String	刪除字串的最後一部分
AppendIfMissing	appends a suffix to the end of the String if not present	如果不存在字尾，則在字串的末尾附加一個字尾
PrependIfMissing	prepends a prefix to the start of the String if not present	如果不存在字首，則在字串的開頭新增字首
LeftPad/RightPad/Center/Repeat	pads a String	填充字串
UpperCase/LowerCase/SwapCase/Capitalize/Uncapitalize	changes the case of a String	更改字串的大小寫
CountMatches	counts the number of occurrences of one String in another	計算一個字串在另一個字串中出現的次數
IsAlpha/IsNumeric/IsWhitespace/IsAsciiPrintable	checks the characters in a String	檢查字串中的字元
DefaultString	protects against a null input String	防止輸入字串為空
Rotate	rotate (circular shift) a String	旋轉（迴圈移位）字串
Reverse/ReverseDelimited	reverses a String -反轉字串
Abbreviate	abbreviates a string using ellipsis or another given String	使用省略號或另一個給定的String縮寫一個字串
Difference	compares Strings and reports on their differences	比較字串並報告其差異
LevenshteinDistance	the number of changes needed to change one String into another	將一個String轉換為另一個String所需的更改次數