public static String toString(Character ch) {
        if (ch == null) {
            return null;
        }
        return toString(ch.charValue());
    }
<p>Converts the character to a String that contains the one character.</p>

<p>For ASCII 7 bit characters, this uses a cache that will return the
same String object each time.</p>

<p>If {@code null} is passed in, {@code null} will be returned.</p>

<pre>
  CharUtils.toString(null) = null
  CharUtils.toString(' ')  = " "
  CharUtils.toString('A')  = "A"
</pre>

@param ch  the character to convert
@return a String containing the one specified character
android/android_framework/base/src/main/java/lang3/CharUtils.java