使用Guava适配不同的callback

1. Cache<Key,Value> cache =CacheBuilder.newBuilder()
2. .maximumSize(1000)
3. .build();// look Ma, no CacheLoader
4. ...
5. try{
6. // If the key wasn't in the "easy to compute" group, we need to
7. // do things the hard way.
8. cache.get(key,newCallable<Value>(){
9. @Override
10. publicValue call()throwsAnyException{
11. return doThingsTheHardWay(key);
12. }
13. });
14. }catch(ExecutionException e){
15. thrownewOtherException(e.getCause());
16. }