Learn about the working principle
Disk LRU CACHE working principle in the Java class library
Overview:
DISK LRU Cache (Disk LRU cache) is a tool for storing and retrieving data. It saves the data on the disk and provides a LRU (Least Recently Used) algorithm to manage disk space and cache cachedata.The design of the tool is to improve the application performance by reducing the disk IO operation and reducing memory overhead.This article will introduce the working principles of Disk Lru Cache in detail and provide some Java code examples for better understanding.
working principle:
DISK LRU CACHE manages data on the disk by dividing the data into multiple fixed -sized blocks.Each block is mapped to a file on the disk and has a fixed size limit.This design makes it possible to quickly read and write data on the disk.
When the data needs to be retrieved from the disk LRU cache, it first finds the data in the memory in the memory.If the data exists in the cache and does not expire (according to a certain expiration strategy), the data is directly returned.If there is no data in the cache, or the data has expired, the data needs to be read from the disk.
When the data is written to the disk LRU cache, it will determine whether the total size of the current cache exceeds the maximum cache size of the preset.If it exceeds, it will eliminate a part of the data based on the LRU algorithm to free up enough space to store new data.The elimination strategy is usually the most recently used data to retain the recent visits to more frequent data.
Implementation:
In the Java library, you can use the Disklrucache class to simplify the use of Disk Lru Cache.Below is a simple example code that demonstrates how to use the DiskLRUCACHE class to achieve a disk LRU cache.
import java.io.File;
import java.io.IOException;
import com.jakewharton.disklrucache.DiskLruCache;
public class DiskLRUCacheExample {
private static final int MAX_CACHE_SIZE = 1024 * 1024 * 10; // 10MB
private static final int VALUE_COUNT = 1;
public static void main(String[] args) {
try {
File cacheDir = new File("path/to/cache/directory");
DiskLruCache cache = DiskLruCache.open(cacheDir, 1, VALUE_COUNT, MAX_CACHE_SIZE);
// data input
Disklrucache.editor editor = cache.edit ("key"); // "key" is the only cache key
Editor.set (0, "value"); // Set the first block of data
editor.commit (); // Submit the modification and write to the disk
// Read the data
DiskLruCache.Snapshot snapshot = cache.get("key");
String value = snapshot.getstring (0); // Get the first piece of data
snapshot.close (); // Turn off the snapshot
// Close the cache
cache.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
In the above example, we first created a DiskLRUCACHE instance and specified the maximum cache size, value and cache directory.Next, create a cache editor by calling the `Edit ()` method, and then set the first piece of data using the `set ()` method, and submit the modification through the `Commit ()`.To read data, we can get a cache snapshot by calling the `Get ()` method, and use the `GetString ()` method to obtain the first piece of data.Finally, turn off the cache by calling the `Close ()" method.
Summarize:
DISK LRU Cache is a tool that effectively manages data on the disk. The performance of the application is improved through the LRU algorithm and the minimization of the disk IO operation.In the Java library, you can use the Disklrucache class to simplify the implementation of the disk LRU cache.The above is a brief introduction to the working principle of DISK LRU CACHE. It also comes with a Java code example, hoping to help readers better understand the theme.
