google guava

引入maven 
<dependency>
    <groupId>com.google.guava</groupId>
    <artifactId>guava</artifactId>
    <version>19.0</version>
</dependency>

//创建缓存
Cache<String, String> cache = CacheBuilder.newBuilder()
                .maximumSize(10000)
                .concurrencyLevel(10)
                .expireAfterWrite(30, TimeUnit.SECONDS)
                .build();

//设置缓存
cache.put("1", "xx");
//获取缓存，没有则返回null
cache.getIfPresent("2");
//获取缓存，没有就设置一个
String v = cache.get("3", () -> "33");