[HADOOP-4210] Findbugs warnings are printed related to equals implementation of several classes

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 0.20.0
• Hadoop Flags: Incompatible change, Reviewed
• Release Note: Changed public class org.apache.hadoop.mapreduce.ID to be an abstract class. Removed from class org.apache.hadoop.mapreduce.ID the methods public static ID read(DataInput in) and public static ID forName(String str).
• Assignee: Suresh Srinivas
• Reporter: Suresh Srinivas
• Due: 19/Sep/08
• Created: 19/Sep/08 01:14
• Updated: 08/Jul/09 16:53
• Resolved: 30/Sep/08 18:54

Description

During compilation - findbugs generates several warnings that indicates bugs in the implementation of equals method. One of the example of this report is:

Bug type EQ_GETCLASS_AND_CLASS_CONSTANT (click for details)
In class org.apache.hadoop.mapred.ID
In method org.apache.hadoop.mapred.ID.equals(Object)
At ID.java:[line 66]
Value doesn't work for subtypes

This class has an equals method that will be broken if it is inherited by subclasses. It compares a class literal with the class of the argument (e.g., in class Foo it might check if Foo.class == o.getClass()). It is better to check if this.getClass() == o.getClass().