public String getPattern() {
        return this.pattern;
    }
<p>
A regular expression used to validate the value of a slot.
</p>
<p>
Use a standard regular expression. Amazon Lex supports the following characters in the regular expression:
</p>
<ul>
<li>
<p>
A-Z, a-z
</p>
</li>
<li>
<p>
0-9
</p>
</li>
<li>
<p>
Unicode characters ("\ u&lt;Unicode&gt;")
</p>
</li>
</ul>
<p>
Represent Unicode characters with four digits, for example "\u0041" or "\u005A".
</p>
<p>
The following regular expression operators are not supported:
</p>
<ul>
<li>
<p>
Infinite repeaters: *, +, or {x,} with no upper bound.
</p>
</li>
<li>
<p>
Wild card (.)
</p>
</li>
</ul>

@return A regular expression used to validate the value of a slot. </p>
        <p>
        Use a standard regular expression. Amazon Lex supports the following characters in the regular
        expression:
        </p>
        <ul>
        <li>
        <p>
        A-Z, a-z
        </p>
        </li>
        <li>
        <p>
        0-9
        </p>
        </li>
        <li>
        <p>
        Unicode characters ("\ u&lt;Unicode&gt;")
        </p>
        </li>
        </ul>
        <p>
        Represent Unicode characters with four digits, for example "\u0041" or "\u005A".
        </p>
        <p>
        The following regular expression operators are not supported:
        </p>
        <ul>
        <li>
        <p>
        Infinite repeaters: *, +, or {x,} with no upper bound.
        </p>
        </li>
        <li>
        <p>
        Wild card (.)
        </p>
        </li>
aws-java-sdk-lexmodelbuilding/src/main/java/com/amazonaws/services/lexmodelbuilding/model/SlotTypeRegexConfiguration.java