isEmpty 和 isBlank 的用法区别,至少一半的人答不上来...

沉默王二2022年7月11日
大约 5 分钟

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文章来源:https://sourl.cn/dRpJ6b

大家好,我是二哥,开发中经常有些小细节容易忽略,这些小细节往往容易导致代码缺陷,今天分享一波工具类的小细节

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

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()

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。

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

/**
 * <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)

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();

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/IsBlankchecks if a String contains text检查字符串是否包含文本
Trim/Stripremoves leading and trailing whitespace删除前导和尾随空格
Equals/Comparecompares two strings null-safe比较两个字符串是否为 null 安全的
startsWithcheck if a String starts with a prefix null-safe检查字符串是否以前缀 null 安全开头
endsWithcheck 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/Containsnull-safe index-of checks包含空安全索引检查
IndexOfAny/LastIndexOfAny/IndexOfAnyBut/LastIndexOfAnyButindex-of any of a set of Strings任意一组字符串的索引
ContainsOnly/ContainsNone/ContainsAnydoes 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/Midnull-safe substring extractions字符串安全提取
SubstringBefore/SubstringAfter/SubstringBetweensubstring extraction relative to other strings -相对其他字符串的字符串提取
Split/Joinsplits 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/Deleteremoves part of a String -删除字符串的一部分
Replace/OverlaySearches 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/Chopremoves the last part of a String删除字符串的最后一部分
AppendIfMissingappends 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
PrependIfMissingprepends 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/Repeatpads a String填充字符串
UpperCase/LowerCase/SwapCase/Capitalize/Uncapitalizechanges the case of a String更改字符串的大小写
CountMatchescounts 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/IsAsciiPrintablechecks the characters in a String检查字符串中的字符
DefaultStringprotects against a null input String防止输入字符串为空
Rotaterotate (circular shift) a String旋转(循环移位)字符串
Reverse/ReverseDelimitedreverses a String -反转字符串
Abbreviateabbreviates 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
Differencecompares Strings and reports on their differences比较字符串并报告其差异
LevenshteinDistancethe 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

程序汪资料链接

转载链接:https://mp.weixin.qq.com/s?__biz=MzA4NzQ0Njc4Ng==&mid=2247504624&idx=1&sn=c47e5413aa4914c7301970e0d217bc88&chksm=903bd69da74c5f8b4d4dc6683b4e34b2750278df3dcb9d13b129e80bad9a435b3d98e4ad3fe6#rdopen in new window,出处:我是程序汪,整理:沉默王二

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