DiskLruCache

xcoding.commons.util.DiskLruCache

```
public class DiskLruCache
```
Taken from the JB source code, can be found in: libcore/luni/src/main/java/libcore/io/DiskLruCache.java or direct link: https://android.googlesource.com/platform/libcore/+/android-4.1.1_r1/luni/src/main/java/libcore/io/DiskLruCache.java A cache that uses a bounded amount of space on a filesystem. Each cache entry has a string key and a fixed number of values. Values are byte sequences, accessible as streams or files. Each value must be between 0 and Integer.MAX_VALUE bytes in length.
The cache stores its data in a directory on the filesystem. This directory must be exclusive to the cache; the cache may delete or overwrite files from its directory. It is an error for multiple processes to use the same cache directory at the same time.
This cache limits the number of bytes that it will store on the filesystem. When the number of stored bytes exceeds the limit, the cache will remove entries in the background until the limit is satisfied. The limit is not strict: the cache may temporarily exceed it while waiting for files to be deleted. The limit does not include filesystem overhead or the cache journal so space-sensitive applications should set a conservative limit.
Clients call DiskLruCache.edit to create or update the values of an entry. An entry may have only one editor at one time; if a value is not available to be edited then DiskLruCache.edit will return null.
- When an entry is being created it is necessary to supply a full set of values; the empty value should be used as a placeholder if necessary.
- When an entry is being edited, it is not necessary to supply data for every value; values default to their previous value.
Every DiskLruCache.edit call must be matched by a call to DiskLruCache.Editor.commit or DiskLruCache.Editor.abort. Committing is atomic: a read observes the full set of values as they were before or after the commit, but never a mix of values.
Clients call DiskLruCache.get to read a snapshot of an entry. The read will observe the value at the time that DiskLruCache.get was called. Updates and removals after the call do not impact ongoing reads.
This class is tolerant of some I/O errors. If files are missing from the filesystem, the corresponding entries will be dropped from the cache. If an error occurs while writing a cache value, the edit will fail silently. Callers should handle other problems by catching IOException and responding appropriately.
另请参阅:

DiskLruCache.edit, DiskLruCache.edit, DiskLruCache.edit, DiskLruCache.Editor.commit, DiskLruCache.Editor.abort, DiskLruCache.get, DiskLruCache.get

嵌套类概要

嵌套类
限定符和类型类和说明

class DiskLruCache.Editor
Edits the values for an entry.

class DiskLruCache.Snapshot
A snapshot of the values for an entry.

嵌套类
限定符和类型	类和说明
`class`	`DiskLruCache.Editor` Edits the values for an entry.
`class`	`DiskLruCache.Snapshot` A snapshot of the values for an entry.

方法概要

所有方法静态方法实例方法具体方法
限定符和类型	方法和说明
`void`	`close()` Closes this cache. Stored values will remain on the filesystem.
`static void`	`closeQuietly()` Closes 'closeable', ignoring any checked exceptions. Does nothing if 'closeable' is null.
`void`	`delete()` Closes the cache and deletes all of its stored values. This will delete all files in the cache directory including files that weren't created by the cache.
`static void`	`deleteContents()` Recursively delete everything in `dir`.
`DiskLruCache.Editor`	`edit()` Returns an editor for the entry named `key`, or null if another edit is in progress.
`void`	`flush()` Force buffered operations to the filesystem.
`DiskLruCache.Snapshot`	`get()` Returns a snapshot of the entry named `key`, or null if it doesn't exist is not currently readable. If a value is returned, it is moved to the head of the LRU queue.
`java.io.File`	`getDirectory()` Returns the directory where this cache stores its data.
`boolean`	`isClosed()` Returns true if this cache has been closed.
`long`	`maxSize()` Returns the maximum number of bytes that this cache should use to store its data.
`static DiskLruCache`	`open()` Opens the cache in `directory`, creating a cache if none exists there.
`static java.lang.String`	`readAsciiLine()` Returns the ASCII characters up to but not including the next "\r\n", or "\n".
`static java.lang.String`	`readFully()` Returns the remainder of 'reader' as a string, closing it when done.
`boolean`	`remove()` Drops the entry for `key` if it exists and can be removed. Entries actively being edited cannot be removed.
`long`	`size()` Returns the number of bytes currently being used to store the values in this cache. This may be greater than the max size if a background deletion is pending.

- 方法详细资料
  - readFully
```
public static java.lang.String readFully()
```
    Returns the remainder of 'reader' as a string, closing it when done.
  - readAsciiLine
```
public static java.lang.String readAsciiLine()
```
    Returns the ASCII characters up to but not including the next "\r\n", or "\n".
    
    抛出:
    
    EOFException - if the stream is exhausted before the next newline character.
  - closeQuietly
```
public static void closeQuietly()
```
    Closes 'closeable', ignoring any checked exceptions. Does nothing if 'closeable' is null.
  - deleteContents
```
public static void deleteContents()
```
    Recursively delete everything in dir.
  - open
```
public static DiskLruCache open()
```
    Opens the cache in directory, creating a cache if none exists there.
    
    抛出:
    
    - if reading or writing the cache directory fails
  - get
```
public DiskLruCache.Snapshot get()
```
    Returns a snapshot of the entry named key, or null if it doesn't exist is not currently readable. If a value is returned, it is moved to the head of the LRU queue.
  - edit
```
public DiskLruCache.Editor edit()
```
    Returns an editor for the entry named key, or null if another edit is in progress.
  - getDirectory
```
public java.io.File getDirectory()
```
    Returns the directory where this cache stores its data.
  - maxSize
```
public long maxSize()
```
    Returns the maximum number of bytes that this cache should use to store its data.
  - size
```
public long size()
```
    Returns the number of bytes currently being used to store the values in this cache. This may be greater than the max size if a background deletion is pending.
  - remove
```
public boolean remove()
```
    Drops the entry for key if it exists and can be removed. Entries actively being edited cannot be removed.
    
    返回:
    
    true if an entry was removed.
  - isClosed
```
public boolean isClosed()
```
    Returns true if this cache has been closed.
  - flush
```
public void flush()
```
    Force buffered operations to the filesystem.
  - close
```
public void close()
```
    Closes this cache. Stored values will remain on the filesystem.
  - delete
```
public void delete()
```
    Closes the cache and deletes all of its stored values. This will delete all files in the cache directory including files that weren't created by the cache.

类 DiskLruCache

嵌套类概要

方法概要

方法详细资料

readFully

readAsciiLine

closeQuietly

deleteContents

open

get

edit

getDirectory

maxSize

size

remove

isClosed

flush

close

delete