Guava caching tutorial: a magical tool to improve program efficiency

Guava cache usage tutorial: The secret weapon to improve program efficiency

Guava cache is an efficient caching library in Java that can help you significantly improve the performance of your program. It provides multiple caching strategies, such as LRU (least recently used) and LFU (least frequently used), as well as multiple cache loading methods, such as local loading and remote loading.

Basic usage of cache

Using Guava cache is very simple and only requires a few lines of code. First, you need to create a cache instance. You can use the following code to create an LRU cache with a maximum capacity of 100:

LoadingCache<Key, Value> cache = CacheBuilder.newBuilder()
    .maximumSize(100)
    .build(new CacheLoader<Key, Value>() {
        @Override
        public Value load(Key key) throws Exception {
            // 从数据库或其他数据源加载数据
            return loadFromDataSource(key);
        }
    });

Then, you can use the cache to store and retrieve data. You can use the following code to store data into the cache:

cache.put(key, value);

You can also use the following code to get data from the cache:

Value value = cache.get(key);

If the data does not exist in the cache, ## will be called #CacheLoader.load()Method loads data from the data source.

Cache configuration

You can configure various parameters of the cache through the

CacheBuilder class, including maximum capacity, expiration time, eviction policy, etc. For example, you can use the following code to create an LRU cache with a maximum capacity of 100 and an expiration time of 10 minutes:

LoadingCache<Key, Value> cache = CacheBuilder.newBuilder()
    .maximumSize(100)
    .expireAfterWrite(10, TimeUnit.MINUTES)
    .build(new CacheLoader<Key, Value>() {
        @Override
        public Value load(Key key) throws Exception {
            // 从数据库或其他数据源加载数据
            return loadFromDataSource(key);
        }
    });

You can also configure the cache eviction policy through the

CacheBuilder class. For example, you can use the following code to create an LRU cache that evicts the least recently used data when the cache is full:

LoadingCache<Key, Value> cache = CacheBuilder.newBuilder()
    .maximumSize(100)
    .expireAfterWrite(10, TimeUnit.MINUTES)
    .removalListener(new RemovalListener<Key, Value>() {
        @Override
        public void onRemoval(RemovalNotification<Key, Value> notification) {
            // 处理被驱逐的数据
        }
    })
    .build(new CacheLoader<Key, Value>() {
        @Override
        public Value load(Key key) throws Exception {
            // 从数据库或其他数据源加载数据
            return loadFromDataSource(key);
        }
    });

Cache usage scenarios

Guava cache can be used for a variety of purposes Scenarios, for example:

Caching database query results: You can cache the database query results, so that the next time you query, you can get the data directly from the cache without querying the database again.
• Caching remote API call results: You can cache the remote API call results, so that the next time you call, you can get the data directly from the cache without calling the remote API again.
• Cache file content: You can cache the file content so that the next time you read the file, you can read the data directly from the cache without reading the file again.

Caching precautions

When using Guava cache, you need to pay attention to the following points:

The cache has limited capacity, so you need to regularly Clean the cache to prevent it from getting too large.
• Cached data may become outdated, so you need to update the cache regularly to ensure that the data in the cache is up to date.
• The cached data may be modified by other threads, so you need to synchronize the cached data to prevent data inconsistency.

Summary

Guava cache is a very powerful tool that can help you significantly improve the performance of your program. If you need to use caching in your program, Guava caching is a very good choice.

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