Understand the technical principles and applications of the "Disk Lru Cache" framework in the Java library

The "DISK LRU CACHE" framework in the Java library is a technology used to cache data on a disk.It uses Least Recently Used (LRU) algorithm to manage data in the cache to ensure that the oldest and most commonly used data are replaced, thereby maintaining the effectiveness and performance of the cache. Technical principle: The core principle of the Disk Lru Cache framework is to store data on the disk and use index files and data files to manage and maintain data in the cache.The following is the general technical principle of the framework: 1. Data storage: The cache data is stored in the data file in the form in the form of key value pair.Each key value corresponds to a unique file name.This framework tracks the position of the data by maintaining the mapping relationship between the key and the file name in the index file. 2. LRU algorithm: The framework uses the LRU algorithm to determine which data is the least commonly used.When the cache space is insufficient, the oldest data will be replaced so that the new data can be cached. 3. Caches: When you need to obtain data from the cache, the framework first checks the index file to obtain the file name of the data.Then, it reads the corresponding data files on the disk through the file name and loads the data to the memory.This can avoid frequent access to disks and improve reading performance. 4. Data writing: When the new data needs to be cached, the framework will write the data to the data file on the disk, and update the index file to contain the new key value pair.If there is insufficient cache space, the framework will replace the most commonly used data based on the LRU algorithm. Application of framework: The DISK LRU Cache framework can be used in applications that need to catch a large amount of data to speed up the read and access speed of data.The following is one of the main application scenarios of the framework: 1. Picture cache: In Android applications, loading and displaying pictures are common tasks.Use the DISK LRU CACHE framework to cache pictures that have been loaded on the disk to quickly access when needed.This can improve the response speed of the application and save network bandwidth, because the picture does not need to be downloaded repeatedly. Code example and configuration: Here are a simple sample code using the Disk Lru Cache framework to implement the function of the picture cache: DiskLruCache cache = DiskLruCache.open(cacheDir, appVersion, valueCount, maxSize); String imageUrl = "https://example.com/image.jpg"; String cacheKey = generateCacheKey(imageUrl); DiskLruCache.Editor editor = cache.edit(cacheKey); if (editor != null) { OutputStream outputStream = editor.newOutputStream(0); if (downloadImage(imageUrl, outputStream)) { editor.commit(); } else { editor.abort(); } } ... InputStream inputStream = cache.get(cacheKey).getInputStream(); Bitmap bitmap = BitmapFactory.decodeStream(inputStream); imageView.setImageBitmap(bitmap); In the above example, we first created a DiskLRUCACHE instance, specifying the cache directory, application version, the number of keys, and maximum cache size.We then use the URL of the picture to generate a unique cache key to store it in the cache.By calling the `Cache.edit ()" method, we can get an Editor object for editing the cache.We can use the OutputStream provided by the Editor object to write the picture data into the cache.Finally, we can use the cache key to obtain inputStream from the cache and decodate it as bitmap, and then display it in ImageView. In addition, the performance and behavior of the Disk Lru Cache framework can be optimized by related configurations.For example, you can adjust the size of the cache, set the cache period or maximum cache item. In summary, the Disk Lru Cache framework is an efficient disk cache technology, which has a wide range of application prospects in applications that need to cache large amounts of data.By reasonable configuration and use of this framework, the performance and response speed of the application can be improved.