[jira] [Created] (REEF-791) Replace inefficient use of keySet iterator with entrySet iterator

["Dongjoon Hyun (JIRA)" <ji...@apache.org>]

Dongjoon Hyun created REEF-791:
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             Summary: Replace inefficient use of keySet iterator with entrySet iterator
                 Key: REEF-791
                 URL: https://issues.apache.org/jira/browse/REEF-791
             Project: REEF
          Issue Type: Improvement
    Affects Versions: 0.12
            Reporter: Dongjoon Hyun
            Assignee: Dongjoon Hyun
            Priority: Trivial
             Fix For: 0.13


We can improve performance by replacing `keySet` with `entrySet`. For example, see the following code pattern change in REEF-Wake.
{code}
-    for (final Class<? extends T> clazz : clazzToCodecMap.keySet()) {
-      clazzToEncoderMap.put(clazz, clazzToCodecMap.get(clazz));
-      clazzToDecoderMap.put(clazz, clazzToCodecMap.get(clazz));
+    for (final Entry<Class<? extends T>, Codec<? extends T>> e : clazzToCodecMap.entrySet()) {
+      clazzToEncoderMap.put(e.getKey(), e.getValue());
+      clazzToDecoderMap.put(e.getKey(), e.getValue());
{code}

As of today, we can find 6 candidates.
 * reef-io
  * CodecRamMap.java
 * reef-tang
  * CommandLine.java
  * InjectorImpl.java
  * Tint.java
 * reef-util
  * CacheImpl.java
 * reef-wake
  * MultiCodec.java

We can improve all except `InjectorImpl.java' using `TracingMonotonicTreeMap.java' that doesn't support `entrySet`.



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