为什么操作bucket就会出现错误，初始化连接未出现错误，求助热心人

Exception in thread "main" com.aliyun.oss.ClientException: mypic2.oss-cn-hangzhou-internal.aliyuncs.com
[ErrorCode]: UnknownHost
[RequestId]: Unknown
    at com.aliyun.oss.common.utils.ExceptionFactory.createNetworkException(ExceptionFactory.java:65)
    at com.aliyun.oss.common.comm.DefaultServiceClient.sendRequestCore(DefaultServiceClient.java:62)
    at com.aliyun.oss.common.comm.ServiceClient.sendRequestImpl(ServiceClient.java:126)
    at com.aliyun.oss.common.comm.ServiceClient.sendRequest(ServiceClient.java:72)
    at com.aliyun.oss.internal.OSSOperation.send(OSSOperation.java:92)
    at com.aliyun.oss.internal.OSSOperation.doOperation(OSSOperation.java:133)
    at com.aliyun.oss.internal.OSSOperation.doOperation(OSSOperation.java:111)
    at com.aliyun.oss.internal.OSSBucketOperation.listObjects(OSSBucketOperation.java:323)
    at com.aliyun.oss.OSSClient.listObjects(OSSClient.java:388)
    at com.aliyun.oss.OSSClient.listObjects(OSSClient.java:376)
    at UploadPartCopySample.main(UploadPartCopySample.java:55)
Caused by: java.net.UnknownHostException: mypic2.oss-cn-hangzhou-internal.aliyuncs.com
    at java.net.InetAddress.getAllByName0(InetAddress.java:1156)
    at java.net.InetAddress.getAllByName(InetAddress.java:1082)
    at java.net.InetAddress.getAllByName(InetAddress.java:1018)
    at org.apache.http.impl.conn.SystemDefaultDnsResolver.resolve(SystemDefaultDnsResolver.java:45)
    at org.apache.http.impl.conn.DefaultClientConnectionOperator.resolveHostname(DefaultClientConnectionOperator.java:259)
    at org.apache.http.impl.conn.DefaultClientConnectionOperator.openConnection(DefaultClientConnectionOperator.java:159)
    at org.apache.http.impl.conn.ManagedClientConnectionImpl.open(ManagedClientConnectionImpl.java:304)
    at org.apache.http.impl.client.DefaultRequestDirector.tryConnect(DefaultRequestDirector.java:611)
    at org.apache.http.impl.client.DefaultRequestDirector.execute(DefaultRequestDirector.java:446)
    at org.apache.http.impl.client.AbstractHttpClient.doExecute(AbstractHttpClient.java:882)