public GetItemRequest withExpressionAttributeNames(java.util.Map<String, String> expressionAttributeNames) {
        setExpressionAttributeNames(expressionAttributeNames);
        return this;
    }
public GetItemRequest withExpressionAttributeNames ( java . util . Map < String , String > expressionAttributeNames ) { setExpressionAttributeNames ( expressionAttributeNames ) ; return this ; }
<p>
One or more substitution tokens for attribute names in an expression. The following are some use cases for using
<code>ExpressionAttributeNames</code>:
</p>
<ul>
<li>
<p>
To access an attribute whose name conflicts with a DynamoDB reserved word.
</p>
</li>
<li>
<p>
To create a placeholder for repeating occurrences of an attribute name in an expression.
</p>
</li>
<li>
<p>
To prevent special characters in an attribute name from being misinterpreted in an expression.
</p>
</li>
</ul>
<p>
Use the <b>#</b> character in an expression to dereference an attribute name. For example, consider the following
attribute name:
</p>
<ul>
<li>
<p>
<code>Percentile</code>
</p>
</li>
</ul>
<p>
The name of this attribute conflicts with a reserved word, so it cannot be used directly in an expression. (For
the complete list of reserved words, see <a
href="https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/ReservedWords.html">Reserved Words</a> in
the <i>Amazon DynamoDB Developer Guide</i>). To work around this, you could specify the following for
<code>ExpressionAttributeNames</code>:
</p>
<ul>
<li>
<p>
<code>{"#P":"Percentile"}</code>
</p>
</li>
</ul>
<p>
You could then use this substitution in an expression, as in this example:
</p>
<ul>
<li>
<p>
<code>#P = :val</code>
</p>
</li>
</ul>
<note>
<p>
Tokens that begin with the <b>:</b> character are <i>expression attribute values</i>, which are placeholders for
the actual value at runtime.
</p>
</note>
<p>
For more information on expression attribute names, see <a href=
"https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/Expressions.AccessingItemAttributes.html"
>Accessing Item Attributes</a> in the <i>Amazon DynamoDB Developer Guide</i>.
</p>

@param expressionAttributeNames
One or more substitution tokens for attribute names in an expression. The following are some use cases for
using <code>ExpressionAttributeNames</code>:</p>
<ul>
<li>
<p>
To access an attribute whose name conflicts with a DynamoDB reserved word.
</p>
</li>
<li>
<p>
To create a placeholder for repeating occurrences of an attribute name in an expression.
</p>
</li>
<li>
<p>
To prevent special characters in an attribute name from being misinterpreted in an expression.
</p>
</li>
</ul>
<p>
Use the <b>#</b> character in an expression to dereference an attribute name. For example, consider the
following attribute name:
</p>
<ul>
<li>
<p>
<code>Percentile</code>
</p>
</li>
</ul>
<p>
The name of this attribute conflicts with a reserved word, so it cannot be used directly in an expression.
(For the complete list of reserved words, see <a
href="https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/ReservedWords.html">Reserved
Words</a> in the <i>Amazon DynamoDB Developer Guide</i>). To work around this, you could specify the
following for <code>ExpressionAttributeNames</code>:
</p>
<ul>
<li>
<p>
<code>{"#P":"Percentile"}</code>
</p>
</li>
</ul>
<p>
You could then use this substitution in an expression, as in this example:
</p>
<ul>
<li>
<p>
<code>#P = :val</code>
</p>
</li>
</ul>
<note>
<p>
Tokens that begin with the <b>:</b> character are <i>expression attribute values</i>, which are
placeholders for the actual value at runtime.
</p>
</note>
<p>
For more information on expression attribute names, see <a href=
"https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/Expressions.AccessingItemAttributes.html"
>Accessing Item Attributes</a> in the <i>Amazon DynamoDB Developer Guide</i>.
@return Returns a reference to this object so that method calls can be chained together.