public MetricDataQuery withExpression(String expression) {
        setExpression(expression);
        return this;
    }
<p>
The math expression to perform on the returned data, if this object is performing a math expression. This
expression can use the <code>Id</code> of the other metrics to refer to those metrics, and can also use the
<code>Id</code> of other expressions to use the result of those expressions.
</p>
<p>
Conditional: Within each <code>MetricDataQuery</code> object, you must specify either <code>Expression</code> or
<code>MetricStat</code>, but not both.
</p>

@param expression
       The math expression to perform on the returned data, if this object is performing a math expression. This
       expression can use the <code>Id</code> of the other metrics to refer to those metrics, and can also use
       the <code>Id</code> of other expressions to use the result of those expressions. </p>
       <p>
       Conditional: Within each <code>MetricDataQuery</code> object, you must specify either
       <code>Expression</code> or <code>MetricStat</code>, but not both.
@return Returns a reference to this object so that method calls can be chained together.
aws-java-sdk-autoscaling/src/main/java/com/amazonaws/services/autoscaling/model/MetricDataQuery.java