The ejb-jar.xml visual editor lets you edit the general for an EJB module. You open the editor by expanding the project's Configuration Files node in the Projects window and double-clicking ejb-jar.xml. The Enterprise Beans section of the Overview view contains a section for each of your EJB module's enterprise beans.
When you click CMP Relationships at the top of the editor, you can edit the container-managed relationships between the CMP entity beans in the EJB module. For each relationship, specify the following:
If the multiplicity is set to many, you can choose whether to return java.util.Set or java.util.Collection. Choose java.util.Set if the returned beans cannot be duplicates. Choose java.util.Collection if the returned beans can include duplicates.