StoredContainer (Sleepycat Software, Inc. - Berkeley DB Java API)
Keywords: com.sleepycat.collections.StoredContainer class

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## com.sleepycat.collections
Class StoredContainer

    java.lang.Object
      com.sleepycat.collections.StoredContainer

All Implemented Interfaces:
  Cloneable

Direct Known Subclasses:
  StoredCollection, StoredMap

public abstract class StoredContainer
extends Object
implements Cloneable

A abstract base class for all stored collections and maps. This class provides implementations of methods that are common to the `Collection` and the `Map` interfaces, namely `clear()`, `isEmpty()` and `size()`.

Note that this class does not conform to the standard Java collections interface in the following ways:

- The `size()` method always throws `UnsupportedOperationException` because, for performance reasons, databases do not maintain their total record count.
- All iterators must be explicitly closed using `StoredIterator.close()` or `StoredIterator.close(java.util.Iterator)` to release the underlying database cursor resources.

In addition, this class provides the following methods for stored collections only. Note that the use of these methods is not compatible with the standard Java collections interface.

- `isWriteAllowed()`
- `isSecondary()`
- `isOrdered()`
- `areDuplicatesAllowed()`
- `areDuplicatesOrdered()`
- `areKeysRenumbered()`
- `isDirtyReadAllowed()`
- `isDirtyRead()`
- `isTransactional()`

Method Summary
`boolean` | `areDuplicatesAllowed()` Returns whether duplicate keys are allowed in this container.
`boolean` | `areDuplicatesOrdered()` Returns whether duplicate keys are allowed and sorted by element value.
`boolean` | `areKeysRenumbered()` Returns whether keys are renumbered when insertions and deletions occur.
`void` | `clear()` Removes all mappings or elements from this map or collection (optional operation).
`boolean` | `isDirtyRead()` Returns whether dirty-read is enabled for this container.
`boolean` | `isDirtyReadAllowed()` Returns whether dirty-read is allowed for this container.
`boolean` | `isEmpty()` Returns true if this map or collection contains no mappings or elements.
`boolean` | `isOrdered()` Returns whether keys are ordered in this container.
`boolean` | `isSecondary()` Returns whether this container is a view on a secondary database rather than directly on a primary database.
`boolean` | `isTransactional()` Returns whether the databases underlying this container are transactional.
`boolean` | `isWriteAllowed()` Returns true if this is a read-write container or false if this is a read-only container.
`int` | `size()` Always throws UnsupportedOperationException.

Methods inherited from class java.lang.Object
`equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Method Detail

### isWriteAllowed

    public final boolean isWriteAllowed()

  Returns true if this is a read-write container or false if this is a read-only container. This method does not exist in the standard `Map` or `Collection` interfaces.

  Returns:
    whether write is allowed.

### isDirtyReadAllowed

    public final boolean isDirtyReadAllowed()

  Returns whether dirty-read is allowed for this container. For the JE product, dirty-read is always allowed; for the DB product, dirty-read is allowed if it was configured for the underlying database for this container. Even when dirty-read is allowed it must specifically be enabled by calling one of the `StoredCollections` methods. This method does not exist in the standard `Map` or `Collection` interfaces.

  Returns:
    whether dirty-read is allowed.

### isDirtyRead

    public final boolean isDirtyRead()

  Returns whether dirty-read is enabled for this container. If dirty-read is enabled, data will be read that is modified but not committed. Dirty-read is disabled by default. This method always returns false if `isDirtyReadAllowed()` returns false. This method does not exist in the standard `Map` or `Collection` interfaces.

  Returns:
    whether dirty-read is enabled.

### isTransactional

    public final boolean isTransactional()

  Returns whether the databases underlying this container are transactional. Even in a transactional environment, a database will be transactional only if it was opened within a transaction or if the auto-commit option was specified when it was opened. This method does not exist in the standard `Map` or `Collection` interfaces.

  Returns:
    whether the database is transactional.

### areDuplicatesAllowed

    public final boolean areDuplicatesAllowed()

  Returns whether duplicate keys are allowed in this container. Duplicates are optionally allowed for HASH and BTREE databases. This method does not exist in the standard `Map` or `Collection` interfaces.

  Returns:
    whether duplicates are allowed.

### areDuplicatesOrdered

    public final boolean areDuplicatesOrdered()

  Returns whether duplicate keys are allowed and sorted by element value. Duplicates are optionally sorted for HASH and BTREE databases. This method does not exist in the standard `Map` or `Collection` interfaces.

  Returns:
    whether duplicates are ordered.

### areKeysRenumbered

    public final boolean areKeysRenumbered()

  Returns whether keys are renumbered when insertions and deletions occur. Keys are optionally renumbered for RECNO databases. This method does not exist in the standard `Map` or `Collection` interfaces.

  Returns:
    whether keys are renumbered.

### isOrdered

    public final boolean isOrdered()

  Returns whether keys are ordered in this container. Keys are ordered for BTREE, RECNO and QUEUE database. This method does not exist in the standard `Map` or `Collection` interfaces.

  Returns:
    whether keys are ordered.

### isSecondary

    public final boolean isSecondary()

  Returns whether this container is a view on a secondary database rather than directly on a primary database. This method does not exist in the standard `Map` or `Collection` interfaces.

  Returns:
    whether the view is for a secondary database.

### size

    public int size()

  Always throws UnsupportedOperationException. The size of a database cannot be obtained reliably or inexpensively. This method therefore violates the `Collection.size()` and `Map.size()` interfaces.

  Returns:
    always throws an exception.
  Throws:
    `UnsupportedOperationException` - unconditionally.

### isEmpty

    public boolean isEmpty()

  Returns true if this map or collection contains no mappings or elements. This method conforms to the `Collection.isEmpty()` and `Map.isEmpty()` interfaces.

  Returns:
    whether the container is empty.
  Throws:
    `RuntimeExceptionWrapper` - if a `DatabaseException` is thrown.

### clear

    public void clear()

  Removes all mappings or elements from this map or collection (optional operation). This method conforms to the `Collection.clear()` and `Map.clear()` interfaces.

  Throws:
    `UnsupportedOperationException` - if the container is read-only.
    `RuntimeExceptionWrapper` - if a `DatabaseException` is thrown.

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Copyright (c) 1996-2004 Sleepycat Software, Inc. - All rights reserved.