UrlCache

```
public interface UrlCache

                    
```
The url cache holds UrlAwares.
A url cache contains several queues for different purpose: reentrant, non-reentrant and n-reentrant. A reentrant queue accepts a url multiple times, a non-reentrant queue accepts a url only once, and a n-reentrant queue accepts a url for n times at most.
Url caches are expected to be very large, the items can be loaded from external source, for example, MongoDB.

Method Summary

Modifier and Type	Method	Description
`abstract Unit`	`removeDeceased()`	Remove dead urls.
`abstract Unit`	`clear()`	Clear the local cache.
`Unit`	`deepClear()`	Clear both the local cache and external source.
`abstract String`	`getName()`	The cache name
`abstract Integer`	`getPriority()`	The priority
`abstract Queue<UrlAware>`	`getNonReentrantQueue()`	A non-reentrant queue accepts the same url only once
`abstract Queue<UrlAware>`	`getNReentrantQueue()`	A non-reentrant queue accepts the same url for n times at most
`abstract Queue<UrlAware>`	`getReentrantQueue()`	A reentrant queue accepts the same url multiple times
`List<Queue<UrlAware>>`	`getQueues()`
`Integer`	`getSize()`
`Integer`	`getExternalSize()`
`Integer`	`getEstimatedExternalSize()`
`Integer`	`getEstimatedSize()`

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

- Method Detail
  - removeDeceased
```
 abstract Unit removeDeceased()
```
    Remove dead urls.
  - clear
```
 abstract Unit clear()
```
    Clear the local cache.
  - deepClear
```
 Unit deepClear()
```
    Clear both the local cache and external source.
  - getName
```
 abstract String getName()
```
    The cache name
  - getPriority
```
 abstract Integer getPriority()
```
    The priority
  - getNonReentrantQueue
```
 abstract Queue<UrlAware> getNonReentrantQueue()
```
    A non-reentrant queue accepts the same url only once
  - getNReentrantQueue
```
 abstract Queue<UrlAware> getNReentrantQueue()
```
    A non-reentrant queue accepts the same url for n times at most
  - getReentrantQueue
```
 abstract Queue<UrlAware> getReentrantQueue()
```
    A reentrant queue accepts the same url multiple times
  - getQueues
```
 List<Queue<UrlAware>> getQueues()
```
  - getSize
```
 Integer getSize()
```
  - getExternalSize
```
 Integer getExternalSize()
```
  - getEstimatedExternalSize
```
 Integer getEstimatedExternalSize()
```
  - getEstimatedSize
```
 Integer getEstimatedSize()
```