package org.odmg;

/**
 * This interface defines the operations associated with an ODMG bag collection.
 * All of the operations defined by the JavaSoft <code>Collection</code>
 * interface are supported by an ODMG implementation of <code>DBag</code>,
 * the exception <code>UnsupportedOperationException</code> is not thrown when a
 * call is made to any of the <code>Collection</code> methods.
 * @author	David Jordan (as Java Editor of the Object Data Management Group)
 * @version ODMG 3.0
 */
// * @see java.lang.UnsupportedOperationException

public interface DBag extends DCollection
{
    /**
     * A new <code>DBag</code> instance is created that is the union of this object
     * and <code>otherBag</code>.
     * This method is similar to the <code>addAll</code> method in <code>Collection</code>,
     * except that this method creates a new collection and <code>addAll</code>
     * modifies the object to contain the result.
     * @param	otherBag	The other bag to use in the union operation.
     * @return A <code>DBag</code> instance that contains the union of this object
     * and <code>otherBag</code>.
     */
// * @see	com.sun.java.util.collections.Collection#addAll
    public DBag union(DBag otherBag);

    /**
     * A new <code>DBag</code> instance is created that contains the intersection of
     * this object and the <code>DBag</code> referenced by <code>otherBag</code>.
     * This method is similar to the <code>retainAll</code> method in <code>Collection</code>,
     * except that this method creates a new collection and <code>retainAll</code>
     * modifies the object to contain the result.
     * @param	otherBag The other bag to use in creating the intersection.
     * @return A <code>DBag</code> instance that contains the intersection of this
     * object and <code>otherBag</code>.
     */
// @see com.sun.java.util.collections.Collection#retainAll
    public DBag intersection(DBag otherBag);

    /**
     * A new <code>DBag</code> instance is created that contains the difference of
     * this object and the <code>DBag</code> instance referenced by <code>otherBag</code>.
     * This method is similar to the <code>removeAll</code> method in <code>Collection</code>,
     * except that this method creates a new collection and <code>removeAll</code>
     * modifies the object to contain the result.
     * @param	otherBag The other bag to use in creating the difference.
     * @return A <code>DBag</code> instance that contains the elements of this object
     * minus the elements in <code>otherBag</code>.
     */
// * @see com.sun.java.util.collections.Collection#removeAll
    public DBag difference(DBag otherBag);

    /**
     * This method returns the number of occurrences of the object <code>obj</code>
     * in the <code>DBag</code> collection.
     * @param obj The value that may have elements in the collection.
     * @return The number of occurrences of <code>obj</code> in this collection.
     */
    public int occurrences(Object obj);
}