public Thumbnails withAspectRatio(String aspectRatio) {
        setAspectRatio(aspectRatio);
        return this;
    }
<important>
<p>
To better control resolution and aspect ratio of thumbnails, we recommend that you use the values
<code>MaxWidth</code>, <code>MaxHeight</code>, <code>SizingPolicy</code>, and <code>PaddingPolicy</code> instead
of <code>Resolution</code> and <code>AspectRatio</code>. The two groups of settings are mutually exclusive. Do
not use them together.
</p>
</important>
<p>
The aspect ratio of thumbnails. Valid values include:
</p>
<p>
<code>auto</code>, <code>1:1</code>, <code>4:3</code>, <code>3:2</code>, <code>16:9</code>
</p>
<p>
If you specify <code>auto</code>, Elastic Transcoder tries to preserve the aspect ratio of the video in the
output file.
</p>

@param aspectRatio
       <p>
       To better control resolution and aspect ratio of thumbnails, we recommend that you use the values
       <code>MaxWidth</code>, <code>MaxHeight</code>, <code>SizingPolicy</code>, and <code>PaddingPolicy</code>
       instead of <code>Resolution</code> and <code>AspectRatio</code>. The two groups of settings are mutually
       exclusive. Do not use them together.
       </p>
       </important>
       <p>
       The aspect ratio of thumbnails. Valid values include:
       </p>
       <p>
       <code>auto</code>, <code>1:1</code>, <code>4:3</code>, <code>3:2</code>, <code>16:9</code>
       </p>
       <p>
       If you specify <code>auto</code>, Elastic Transcoder tries to preserve the aspect ratio of the video in
       the output file.
@return Returns a reference to this object so that method calls can be chained together.
aws-java-sdk-elastictranscoder/src/main/java/com/amazonaws/services/elastictranscoder/model/Thumbnails.java