Java技术-isEmpty 和 isBlank 的用法区别

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, 他们都是org.apache.commons.lang3.StringUtils;这个工具类中的方法

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

?源码分析：

    /**
     *
     * <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;
    }

针对源码的分析，只可以看到对字符串的null判断和长度是否为0进行判断，例如带有空格的空字符串，长度是不为0的并且不为空，所以是可以通过的。

StringUtils.isNotEmpty()

相当于不为空 , = !isEmpty()

源码分析：

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

?源码分析：

/**
     * @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) {      
return !isAnyEmpty(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

     /**
     * <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

?也可以去StringUtils (Apache Commons Lang 3.14.0 API)去查看一下其他的用法。