Better to check the reflexive property of the object while overriding equals
method of it
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Key: MAPREDUCE-2249
URL: https://issues.apache.org/jira/browse/MAPREDUCE-2249
Project: Hadoop Map/Reduce
Issue Type: Improvement
Components: jobtracker, tasktracker
Affects Versions: 0.21.0
Environment: NA
Reporter: Bhallamudi Venkata Siva Kamesh
Fix For: 0.22.0, 0.23.0
It is better to check the reflexive property of the object while overriding
equals method of it.
It improves the performance when a heavy object is compared to itself.
For example pls find the below snippet from Counters.java
{code:title=Current Implementation|borderStyle=solid}
@Override
public synchronized boolean equals(Object obj) {
boolean isEqual = false;
if (obj != null && obj instanceof Counters) {
Counters other = (Counters) obj;
if (size() == other.size()) {
isEqual = true;
for (Map.Entry<String, Group> entry : this.counters.entrySet()) {
String key = entry.getKey();
Group sourceGroup = entry.getValue();
Group targetGroup = other.getGroup(key);
if (!sourceGroup.equals(targetGroup)) {
isEqual = false;
break;
}
}
}
}
return isEqual;
}
{code}
{code:title=Proposed Implementation|borderStyle=solid}
@Override
public synchronized boolean equals(Object obj) {
if(this == obj) {
return true;
}
boolean isEqual = false;
if (obj != null && obj instanceof Counters) {
Counters other = (Counters) obj;
if (size() == other.size()) {
isEqual = true;
for (Map.Entry<String, Group> entry : this.counters.entrySet()) {
String key = entry.getKey();
Group sourceGroup = entry.getValue();
Group targetGroup = other.getGroup(key);
if (!sourceGroup.equals(targetGroup)) {
isEqual = false;
break;
}
}
}
}
return isEqual;
}
{code}
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