[Java]apache.commons.lang3中StringUtils的isEmpty和isBlank等等的区别和用法

2022-08-01 488点热度 0人点赞 0条评论

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

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/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

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