| /** |
| * Licensed to the Apache Software Foundation (ASF) under one |
| * or more contributor license agreements. See the NOTICE file |
| * distributed with this work for additional information |
| * regarding copyright ownership. The ASF licenses this file |
| * to you under the Apache License, Version 2.0 (the |
| * "License"); you may not use this file except in compliance |
| * with the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| package org.apache.hadoop.fs; |
| |
| import org.apache.hadoop.classification.InterfaceAudience; |
| import org.apache.hadoop.classification.InterfaceStability; |
| |
| /** |
| * Opaque interface that identifies a disk location. Subclasses |
| * should implement {@link Comparable} and override both equals and hashCode. |
| */ |
| @InterfaceStability.Unstable |
| @InterfaceAudience.Public |
| public interface VolumeId extends Comparable<VolumeId> { |
| |
| /** |
| * Represents an invalid Volume ID (ID for unknown content). |
| */ |
| public static final VolumeId INVALID_VOLUME_ID = new VolumeId() { |
| |
| @Override |
| public int compareTo(VolumeId arg0) { |
| // This object is equal only to itself; |
| // It is greater than null, and |
| // is always less than any other VolumeId: |
| if (arg0 == null) { |
| return 1; |
| } |
| if (arg0 == this) { |
| return 0; |
| } else { |
| return -1; |
| } |
| } |
| |
| @Override |
| public boolean equals(Object obj) { |
| // this object is equal only to itself: |
| return (obj == this); |
| } |
| |
| @Override |
| public int hashCode() { |
| return Integer.MIN_VALUE; |
| } |
| |
| @Override |
| public boolean isValid() { |
| return false; |
| } |
| |
| @Override |
| public String toString() { |
| return "Invalid VolumeId"; |
| } |
| }; |
| |
| /** |
| * Indicates if the disk identifier is valid. Invalid identifiers indicate |
| * that the block was not present, or the location could otherwise not be |
| * determined. |
| * |
| * @return true if the disk identifier is valid |
| */ |
| public boolean isValid(); |
| |
| @Override |
| abstract public int compareTo(VolumeId arg0); |
| |
| @Override |
| abstract public int hashCode(); |
| |
| @Override |
| abstract public boolean equals(Object obj); |
| |
| } |