public static String defaultString(String str) {
        return str == null ? EMPTY : str;
    }
<p>Returns either the passed in String,
or if the String is {@code null}, an empty String ("").</p>

<pre>
StringUtils.defaultString(null)  = ""
StringUtils.defaultString("")    = ""
StringUtils.defaultString("bat") = "bat"
</pre>

@see ObjectUtils#toString(Object)
@see String#valueOf(Object)
@param str  the String to check, may be null
@return the passed in String, or the empty String if it
 was {@code null}
android/android_framework/base/src/main/java/lang3/StringUtils.java