Java技术-isEmpty 和 isBlank 的用法区别-编程知识

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);}