isEmpty 和 isBlank 的用法区别，至少一半的人答不上来...

代码语言：javascript复制

文章来源：https://sourl.cn/dRpJ6b

也许你两个都不知道,也许你除了isEmpty/isNotEmpty/isNotBlank/isBlank外,并不知道还有isAnyEmpty/isNoneEmpty/isAnyBlank/isNoneBlank的存在, come on ,让我们一起来探索org.apache.commons.lang3.StringUtils;这个工具类。

isEmpty系列

StringUtils.isEmpty()

是否为空. 可以看到 " " 空格是会绕过这种空判断,因为是一个空格,并不是严格的空值,会导致 isEmpty(" ")=false

代码语言：javascript复制

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()

相当于不为空 , = !isEmpty()。

代码语言：javascript复制

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

StringUtils.isAnyEmpty()

是否有一个为空,只有一个为空,就为true。

代码语言：javascript复制

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()

相当于!isAnyEmpty(css) , 必须所有的值都不为空才返回true

代码语言：javascript复制

/**
 * <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) {

isBank系列

StringUtils.isBlank()

是否为真空值(空格或者空值)

代码语言：javascript复制

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()

是否真的不为空,不是空格或者空值 ,相当于!isBlank();

代码语言：javascript复制

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)

代码语言：javascript复制

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

代码语言：javascript复制

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

可以参考官方的文档,里面有详细的描述,有些方法还是很好用的。

https://commons.apache.org/proper/commons-lang/apidocs/org/apache/commons/lang3/StringUtils.html

方法名	英文解释	中文解释
IsEmpty/IsBlank	checks if a String contains text	检查字符串是否包含文本
Trim/Strip	removes leading and trailing whitespace	删除前导和尾随空格
Equals/Compare	compares two strings null-safe	比较两个字符串是否为null安全的
startsWith	check if a String starts with a prefix null-safe	检查字符串是否以前缀null安全开头
endsWith	check if a String ends with a suffix null-safe	检查字符串是否以后缀null安全结尾
IndexOf/LastIndexOf/Contains	null-safe index-of checks	包含空安全索引检查
IndexOfAny/LastIndexOfAny/IndexOfAnyBut/LastIndexOfAnyBut	index-of any of a set of Strings	任意一组字符串的索引
ContainsOnly/ContainsNone/ContainsAny	does String contains only/none/any of these characters	字符串是否仅包含/无/这些字符中的任何一个
Substring/Left/Right/Mid	null-safe substring extractions	字符串安全提取
SubstringBefore/SubstringAfter/SubstringBetween	substring extraction relative to other strings -相对其他字符串的字符串提取
Split/Join	splits a String into an array of substrings and vice versa	将字符串拆分为子字符串数组，反之亦然
Remove/Delete	removes part of a String -删除字符串的一部分
Replace/Overlay	Searches a String and replaces one String with another	搜索字符串，然后用另一个字符串替换
Chomp/Chop	removes the last part of a String	删除字符串的最后一部分
AppendIfMissing	appends a suffix to the end of the String if not present	如果不存在后缀，则在字符串的末尾附加一个后缀
PrependIfMissing	prepends a prefix to the start of the String if not present	如果不存在前缀，则在字符串的开头添加前缀
LeftPad/RightPad/Center/Repeat	pads a String	填充字符串
UpperCase/LowerCase/SwapCase/Capitalize/Uncapitalize	changes the case of a String	更改字符串的大小写
CountMatches	counts the number of occurrences of one String in another	计算一个字符串在另一个字符串中出现的次数
IsAlpha/IsNumeric/IsWhitespace/IsAsciiPrintable	checks the characters in a String	检查字符串中的字符
DefaultString	protects against a null input String	防止输入字符串为空
Rotate	rotate (circular shift) a String	旋转（循环移位）字符串
Reverse/ReverseDelimited	reverses a String -反转字符串
Abbreviate	abbreviates a string using ellipsis or another given String	使用省略号或另一个给定的String缩写一个字符串
Difference	compares Strings and reports on their differences	比较字符串并报告其差异
LevenshteinDistance	the number of changes needed to change one String into another	将一个String转换为另一个String所需的更改次数

代码语言：javascript复制

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contains null prefix string substring

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