guava缓存创建分为两种，一种是CacheLoader,另一种则是callback方式

CacheLoader:
LoadingCache<String,String> cahceBuilder=CacheBuilder
.newBuilder()
.build(new CacheLoader<String, String>(){
@Override
public String load(String key) throws Exception {
String strProValue="hello "+key+"!";
return strProValue;
}
});
System.out.println(cahceBuilder.apply("begincode"));
System.out.println(cahceBuilder.get("begincode"));
api中推荐使用get方法获取值

callback方式:
Cache<String, String> cache = CacheBuilder.newBuilder().maximumSize(1000).build();
String resultVal = cache.get("code", new Callable<String>() {
public String call() {
String strProValue="begin "+"code"+"!";
return strProValue;
}
});
System.out.println("value : " + resultVal);