code: public JobFlowInstancesConfig withEc2SubnetIds(String... ec2SubnetIds) {
          if (this.ec2SubnetIds == null) {
              setEc2SubnetIds(new com.amazonaws.internal.SdkInternalList<String>(ec2SubnetIds.length));
          }
          for (String ele : ec2SubnetIds) {
              this.ec2SubnetIds.add(ele);
          }
          return this;
      }
docs: <p>
  Applies to clusters that use the instance fleet configuration. When multiple EC2 subnet IDs are specified, Amazon
  EMR evaluates them and launches instances in the optimal subnet.
  </p>
  <note>
  <p>
  The instance fleet configuration is available only in Amazon EMR versions 4.8.0 and later, excluding 5.0.x
  versions.
  </p>
  </note>
  <p>
  <b>NOTE:</b> This method appends the values to the existing list (if any). Use
  {@link #setEc2SubnetIds(java.util.Collection)} or {@link #withEc2SubnetIds(java.util.Collection)} if you want to
  override the existing values.
  </p>
  
  @param ec2SubnetIds
  Applies to clusters that use the instance fleet configuration. When multiple EC2 subnet IDs are specified,
  Amazon EMR evaluates them and launches instances in the optimal subnet.</p> <note>
  <p>
  The instance fleet configuration is available only in Amazon EMR versions 4.8.0 and later, excluding 5.0.x
  versions.
  </p>
  @return Returns a reference to this object so that method calls can be chained together.