The technical principles and practical guidelines of the "Disk Lru Cache" framework in the Java class library
The technical principles and practical guidelines of the "Disk Lru Cache" framework in the Java class library
Overview:
In development, we often need to use cache to improve system performance.The cache can accelerate data reading by reducing the number of access to disk I/O.Among them, "Disk Lru Cache" is a Java class library that uses LRU (Least Recently Use) algorithm to achieve a disk -based cache.This article will introduce the technical principles of the "Disk Lru Cache" framework in detail and provide practical guidelines.
Technical principle:
"Disk Lru Cache" is a disk -based cache framework that stored data on disk instead of memory, which can effectively solve the problem of memory restrictions.Its main technical principles include the following points:
1. LRU algorithm: "Disk LRU Cache" uses the recently recently user to manage the cache.The LRU algorithm determines the frequency of data use based on access time, and removes the minimum use of data out of the cache to free up the space for new data.
2. Index table: In order to achieve efficient search and operation, "Disk Lru Cache" uses the index table to record the data in the cache.Index tables store metadata in the form of key-value pair, such as data size, creation time, etc.
3. Data storage: "Disk Lru Cache" stored the data on the disk in the form of a file.Each data item is stored as a separate file, and the file name is obtained by the data key by a certain hash.
4. Data read and write: When you need to read the cache data, "Disk Lru Cache" first found the file path of the data item through the index table and read the data with file I/O operation.When the data needs to be written to the cache, it generates a unique file name and write the data into the file.
Practice guide:
Here are some practical guidelines that use the "Disk Lru Cache" framework, including code examples and related configurations:
1. Introduction dependencies: Add the following dependencies in the construction file of the project:
<dependency>
<groupId>com.jakewharton</groupId>
<artifactId>disklrucache</artifactId>
<version>2.0.2</version>
</dependency>
2. Create a cache instance: Create a cache instance by calling the method by calling `Disklrucache.open ()` method.You can specify parameters such as the catalog, version number, and maximum cache size.
File cacheDir = new File("path/to/cache");
int appVersion = 1;
int maxSize = 10 * 1024 * 1024; // 10MB
DiskLruCache cache = DiskLruCache.open(cacheDir, appVersion, 1, maxSize);
3. Read and write data: You can use the `Cache.get () method to read the data in the cache, use the` cache.edit () method to write the data.The following is an example code:
String key = "exampleKey";
DiskLruCache.Editor editor = cache.edit(key);
if (editor != null) {
File file = editor.getFile(0);
// Write into the data to the file
// ...
editor.commit (); // Submit writing operation
}
DiskLruCache.Snapshot snapshot = cache.get(key);
if (snapshot != null) {
File file = snapshot.getFile(0);
// Read data from the file
// ...
snapshot.close (); // Turn off the snapshot
}
4. Data clearance and shutdown: In order to ensure that the disk space occupied by the cache does not exceed the maximum limit, you can call the method regularly to clean up the data that is not used.In addition, turn off the cache when the application exits:
cache.flush();
cache.close();
in conclusion:
