com.android.tools.build.apkzlib.utils

Class CachedFileContents<T>

java.lang.Object

com.android.tools.build.apkzlib.utils.CachedFileContents<T>

Type Parameters:

T - the type of cached contents

public class CachedFileContents<T>
extends java.lang.Object

A cache for file contents. The cache allows closing a file and saving in memory its contents (or some related information). It can then be used to check if the contents are still valid at some later time. Typical usage flow is:

 Object fileRepresentation = // ...
 File toWrite = // ...
 // Write file contents and update in memory representation
 CachedFileContents<Object> contents = new CachedFileContents<Object>(toWrite);
 contents.closed(fileRepresentation);

 // Later, when data is needed:
 if (contents.isValid()) {
     fileRepresentation = contents.getCache();
 } else {
     // Re-read the file and recreate the file representation
 }
 

Constructor Summary

Constructors

Constructor and Description
CachedFileContents(java.io.File file) Creates a new contents.

Method Summary

Modifier and Type	Method and Description
void	closed(T cache) Should be called when the file's contents are set and the file closed.
T	getCache() Obtains the cached data set with closed(Object) if the file has not been modified since closed(Object) was invoked.
java.io.File	getFile() Obtains the file used for caching.
boolean	isValid() Are the cached contents still valid? If this method determines that the file has been modified since the last time closed(Object) was invoked.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

CachedFileContents

public CachedFileContents(@Nonnull
                          java.io.File file)

Creates a new contents. When the file is written, closed(Object) should be invoked to set the cache.

Parameters:

file - the file

Method Detail

closed

public void closed(@Nullable
                   T cache)

Should be called when the file's contents are set and the file closed. This will save the cache and register the file's timestamp to later detect if it has been modified.

This method can be called as many times as the file has been written.

Parameters:

cache - an optional cache to save

isValid

public boolean isValid()

Are the cached contents still valid? If this method determines that the file has been modified since the last time closed(Object) was invoked.

Returns:

are the cached contents still valid? If this method returns false, the cache is cleared

getCache

@Nullable
public T getCache()

Obtains the cached data set with closed(Object) if the file has not been modified since closed(Object) was invoked.

Returns:

the last cached data or null if the file has been modified since closed(Object) has been invoked

getFile

@Nonnull
public java.io.File getFile()

Obtains the file used for caching.

Returns:

the file; this file always exists and contains the old (cached) contents of the file