Cache (MollyPages.org Foundation API)

All Known Implementing Classes:

MemoryCache
```
public interface Cache
```
A data cache. This is essentially a wrapper over a collection that allows for objects to be cached for a specified amount of time and expired thereafter. Objects in the cache can expire automatically or can be removed manually.

Version:

1.0 12/29/2001

Method Summary

All Methods Instance Methods Abstract Methods
Modifier and Type	Method and Description
`void`	`clear()` Empties the entire cache by expiring and removing all objects.
`void`	`close()` Closes this cache, which makes all items in the cache unavailable.
`boolean`	`containsKey(Object key)` Returns true if the cache has a valid cached item specified by the key.
`void`	`expire(Object key)` Expires immediately the object specified by the key.
`void`	`extend(Object key, long extendTime)` Adds the specified amount of time to the object (to it's current time left) before that object will be expired.
`Object`	`get(Object key)` Returns the cached item specified by the key.
`Map`	`getAll()` Returns all objects in the cache.
`long`	`getDefaultTTL()` Gets the default TTL in milliseconds.
`long`	`getTimeLeft(Object key)` Returns the amount of time left (in milliseconds) before the object will be expired from the cache.
`boolean`	`isClosed()` Returns true if this cache has been closed, false otherwise.
`Object`	`put(Object key, Object item)` Convenience method that puts an object into the cache that expires in the default TTL.
`Object`	`put(Object key, Object val, long expiry)` Puts the specified object into the cache, mapped with the specified key.
`void`	`setDefaultTTL(long millis)` Sets the default TTL in milliseconds.

- Method Detail
  - clear
```
void clear()
```
    Empties the entire cache by expiring and removing all objects.
  - containsKey
```
boolean containsKey(Object key)
```
    Returns true if the cache has a valid cached item specified by the key. If no item is found for that key or if the item has expired, returns false.
    
    Parameters:
    
    key - typically a String but can be any object
  - get
```
Object get(Object key)
```
    Returns the cached item specified by the key. If no item is found for that key or if the item has expired, returns null.
    
    Parameters:
    
    key - typically a String but can be any object
  - getAll
```
Map getAll()
```
    Returns all objects in the cache. The returned map is implementation specific but will typically contain pairs of all objects in the cache. The item might be encapsulated in another implementation-specific class.
    Modification to this map will affect this cache.
  - put
```
Object put(Object key,
           Object val,
           long expiry)
```
    Puts the specified object into the cache, mapped with the specified key. The object stays in the cache for the specified amount of time, after which it is discarded. If that key already contains a value, then that value is returned by this method (and also replaced by the new value).
    
    Parameters:
    
    key - key with which the specified value is to be associated.
    
    val - value to be associated with the specified key.
    
    expiry - time in milliseconds (from the time the object is put into the cache) before it is expired. Specify -1 for the item to never expire.
  - put
```
Object put(Object key,
           Object item)
```
    Convenience method that puts an object into the cache that expires in the default TTL. The default TTL can be get/set by the setDefaultTTL(long) method and subclasses are free to implement a default TTL as they see fit. If that key already contains a value, then that value is returned by this method (and also replaced by the new value).
  - getTimeLeft
```
long getTimeLeft(Object key)
```
    Returns the amount of time left (in milliseconds) before the object will be expired from the cache.
    If the object specified by the key is not found in the cache, then 0 is returned.
    If the object has already expired, then 0 is returned.
    If the object will never expire, then -1 is returned.
    
    Parameters:
    
    key - the key with which to find the object under consideration.
  - expire
```
void expire(Object key)
```
    Expires immediately the object specified by the key. Overrides any previous setting for that object's expire time.
    
    Parameters:
    
    key - the key with which to find the object under consideration.
  - extend
```
void extend(Object key,
            long extendTime)
```
    Adds the specified amount of time to the object (to it's current time left) before that object will be expired. Overrides any previous setting that the object may have had, such as never expiring. Specify -1 for that object to never expire. Does not work for objects that have already expired.
    
    Parameters:
    
    key - the key with which to find the object under consideration.
    
    extendTime - exntension time in milliseconds, valid values are >= 0 and -1
  - setDefaultTTL
```
void setDefaultTTL(long millis)
```
    Sets the default TTL in milliseconds.
  - getDefaultTTL
```
long getDefaultTTL()
```
    Gets the default TTL in milliseconds.
  - close
```
void close()
```
    Closes this cache, which makes all items in the cache unavailable. Any items needed for later should be taken out of the cache before closing it.
  - isClosed
```
boolean isClosed()
```
    Returns true if this cache has been closed, false otherwise.

Interface Cache

Method Summary

Method Detail

clear

containsKey

get

getAll

put

put

getTimeLeft

expire

extend

setDefaultTTL

getDefaultTTL

close

isClosed