我会用番石榴的Suppliers.memoizeWithExpiration（供应商委托，持续时间长，TimeUnit单位）

public class JdkVersionService {    @Inject    private JdkVersionWebService jdkVersionWebService;    // No need to check too often. once a year will be good :)     private final Supplier<JdkVersion> latestJdkVersionCache = Suppliers.memoizeWithExpiration(jdkVersionSupplier(), 365, TimeUnit.DAYS);    public JdkVersion getLatestJdkVersion() {        return latestJdkVersionCache.get();    }    private Supplier<JdkVersion> jdkVersionSupplier() {        return new Supplier<JdkVersion>() { public JdkVersion get() {     return jdkVersionWebService.checkLatestJdkVersion(); }        };    }}

用JDK 8更新

今天，我将使用JDK 8方法参考和构造函数注入来编写更清晰的代码，以不同的方式编写此代码：

import java.util.concurrent.TimeUnit;import java.util.function.Supplier;import javax.inject.Inject;import org.springframework.stereotype.Service;import com.google.common.base.Suppliers;@Servicepublic class JdkVersionService {    private final Supplier<JdkVersion> latestJdkVersionCache;    @Inject    public JdkVersionService(JdkVersionWebService jdkVersionWebService) {        this.latestJdkVersionCache = Suppliers.memoizeWithExpiration(     jdkVersionWebService::checkLatestJdkVersion,     365, TimeUnit.DAYS        );    }    public JdkVersion getLatestJdkVersion() {        return latestJdkVersionCache.get();    }}