关于Guava缓存详解及使用说明

CacheBuilder.newBuilder()
		// 设置并发级别为cpu核心数，默认为4
		.concurrencyLevel(Runtime.getRuntime().availableProcessors()) 
		.build();

CacheBuilder.newBuilder()
		// 设置初始容量为100
		.initialCapacity(100)
		.build();

CacheBuilder.newBuilder()
		// 设置最大容量为1000
		.maximumSize(1000)
		.build();

LoadingCache<Key, Graph> graphs = CacheBuilder.newBuilder()
       .maximumWeight(100000)
       .weigher(new Weigher<Key, Graph>() {
          public int weigh(Key k, Graph g) {
            return g.vertices().size();
          }
        })
       .build(
           new CacheLoader<Key, Graph>() {
             public Graph load(Key key) { // no checked exception
               return createExpensiveGraph(key);
             }
           });

private static Cache<Integer, Integer> numCache = CacheBuilder.newBuilder()
        .expireAfterWrite(5, TimeUnit.MINUTES)
        .build();

public static void main(String[] args) throws Exception {
    System.out.println(numCache.getIfPresent(1));
    Thread.sleep(1000);
    System.out.println(numCache.getIfPresent(1));
    Thread.sleep(1000);
    numCache.put(1, 5);
    System.out.println(numCache.getIfPresent(1));
    // console: null null 5
}

private static LoadingCache<Integer,Integer> numCache = CacheBuilder.newBuilder().
        expireAfterWrite(5L, TimeUnit.MINUTES).
        maximumSize(5000L).
        build(new CacheLoader<Integer, Integer>() {
            @Override
            public Integer load(Integer key) throws Exception {
                System.out.println("no cache");
                return key * 5;
            }
        });

public static void main(String[] args) throws Exception {
    System.out.println(numCache.get(1));
    Thread.sleep(1000);
    System.out.println(numCache.get(1));
    Thread.sleep(1000);
    numCache.put(1, 6);
    System.out.println(numCache.get(1));
    // console: 5 5 6
}