public Builder setPattern(java.lang.String value) {
      if (value == null) {
        throw new NullPointerException();
      }
      pattern_ = value;
      bitField0_ |= 0x00080000;
      onChanged();
      return this;
    }
<pre>
Optional. Pattern of the Type.STRING to restrict a string to a regular
expression.
</pre>

<code>string pattern = 20 [(.google.api.field_behavior) = OPTIONAL];</code>

@param value The pattern to set.
@return This builder for chaining.
java-vertexai/proto-google-cloud-vertexai-v1/src/main/java/com/google/cloud/vertexai/api/Schema.java