public static boolean isEmpty(final CharSequence cs) {
        return cs == null || cs.length() == 0;
    }
<p>Checks if a CharSequence is empty ("") or null.</p>

<pre>
StringUtils.isEmpty(null)      = true
StringUtils.isEmpty("")        = true
StringUtils.isEmpty(" ")       = false
StringUtils.isEmpty("bob")     = false
StringUtils.isEmpty("  bob  ") = false
</pre>

<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
fastexcel-core/src/main/java/cn/idev/excel/util/StringUtils.java