CmsLruCache (OpenCms Core API, version 10.0.0)

java.lang.Object
- org.opencms.cache.CmsLruCache

```
public class CmsLruCache
extends java.lang.Object
```
Implements an LRU (last recently used) cache.
The idea of this cache is to separate the caching policy from the data structure where the cached objects are stored. The advantage of doing so is, that the CmsFlexLruCache can identify the last-recently-used object in O(1), whereas you would need at least O(n) to traverse the data structure that stores the cached objects. Second, you can easily use the CmsFlexLruCache to get an LRU cache, no matter what data structure is used to store your objects.
The cache policy is affected by the "costs" of the objects being cached. Valuable cache costs might be the byte size of the cached objects for example.
To add/remove cached objects from the data structure that stores them, the objects have to implement the methods defined in the interface I_CmsLruCacheObject to be notified when they are added/removed from the CmsFlexLruCache.

Since:

6.0.0

See Also:
I_CmsLruCacheObject

Constructor Summary

Constructors
Constructor and Description
`CmsLruCache(long theMaxCacheCosts, long theAvgCacheCosts, int theMaxObjectCosts)` The constructor with all options.

Method Summary

Methods
Modifier and Type	Method and Description
`boolean`	`add(I_CmsLruCacheObject theCacheObject)` Adds a new object to this cache.
`void`	`clear()` Removes all cached objects in this cache.
`long`	`getAvgCacheCosts()` Returns the average costs of all cached objects.
`long`	`getMaxCacheCosts()` Returns the max costs of all cached objects.
`int`	`getMaxObjectCosts()` Returns the max allowed costs per cached object.
`int`	`getObjectCosts()` Returns the current costs of all cached objects.
`I_CmsLruCacheObject`	`remove(I_CmsLruCacheObject theCacheObject)` Removes an object from the list of all cached objects in this cache, no matter what position it has inside the list.
`int`	`size()` Returns the count of all cached objects.
`java.lang.String`	`toString()` Returns a string representing the current state of the cache.
`boolean`	`touch(I_CmsLruCacheObject theCacheObject)` Touch an existing object in this cache, in the sense that it's "last-recently-used" state is updated.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

- Constructor Detail
  - CmsLruCache
```
public CmsLruCache(long theMaxCacheCosts,
           long theAvgCacheCosts,
           int theMaxObjectCosts)
```
    The constructor with all options.
    
    Parameters:
    theMaxCacheCosts - the maximum cache costs of all cached objects
    theAvgCacheCosts - the average cache costs of all cached objects
    theMaxObjectCosts - the maximum allowed cache costs per object. Set theMaxObjectCosts to -1 if you don't want to limit the max. allowed cache costs per object
- Method Detail
  - add
```
public boolean add(I_CmsLruCacheObject theCacheObject)
```
    Adds a new object to this cache.
    If add the same object more than once, the object is touched instead.
    
    Parameters:
    theCacheObject - the object being added to the cache
    
    Returns:
    true if the object was added to the cache, false if the object was denied because its cache costs were higher than the allowed max. cache costs per object
  - clear
```
public void clear()
```
    Removes all cached objects in this cache.
  - getAvgCacheCosts
```
public long getAvgCacheCosts()
```
    Returns the average costs of all cached objects.
    
    Returns:
    the average costs of all cached objects
  - getMaxCacheCosts
```
public long getMaxCacheCosts()
```
    Returns the max costs of all cached objects.
    
    Returns:
    the max costs of all cached objects
  - getMaxObjectCosts
```
public int getMaxObjectCosts()
```
    Returns the max allowed costs per cached object.
    
    Returns:
    the max allowed costs per cached object
  - getObjectCosts
```
public int getObjectCosts()
```
    Returns the current costs of all cached objects.
    
    Returns:
    the current costs of all cached objects
  - remove
```
public I_CmsLruCacheObject remove(I_CmsLruCacheObject theCacheObject)
```
    Removes an object from the list of all cached objects in this cache, no matter what position it has inside the list.
    
    Parameters:
    theCacheObject - the object being removed from the list of all cached objects
    
    Returns:
    a reference to the object that was removed
  - size
```
public int size()
```
    Returns the count of all cached objects.
    
    Returns:
    the count of all cached objects
  - toString
```
public java.lang.String toString()
```
    Returns a string representing the current state of the cache.
    
    Overrides:
    
    toString in class java.lang.Object
    
    Returns:
    a string representing the current state of the cache
  - touch
```
public boolean touch(I_CmsLruCacheObject theCacheObject)
```
    Touch an existing object in this cache, in the sense that it's "last-recently-used" state is updated.
    
    Parameters:
    theCacheObject - the object being touched
    
    Returns:
    true if an object was found and touched

Class CmsLruCache

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Constructor Detail

CmsLruCache

Method Detail

add

clear

getAvgCacheCosts

getMaxCacheCosts

getMaxObjectCosts

getObjectCosts

remove

size

toString

touch