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SPARK-2148 Add link to requirements for custom equals() and hashcode() methods #1092

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SPARK-2148 Add link to requirements for custom equals() and hashcode() methods #1092

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9 changes: 9 additions & 0 deletions docs/programming-guide.md
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Expand Up @@ -762,6 +762,11 @@ val counts = pairs.reduceByKey((a, b) => a + b)
We could also use `counts.sortByKey()`, for example, to sort the pairs alphabetically, and finally
`counts.collect()` to bring them back to the driver program as an array of objects.

**Note:** when using custom objects as the key in key-value pair operations, you must be sure that a
custom `equals()` method is accompanied with a matching `hashCode()` method. For full details, see
the contract outlined in the [Object.hashCode()
documentation](http://docs.oracle.com/javase/7/docs/api/java/lang/Object.html#hashCode())

</div>

<div data-lang="java" markdown="1">
Expand Down Expand Up @@ -794,6 +799,10 @@ JavaPairRDD<String, Integer> counts = pairs.reduceByKey((a, b) -> a + b);
We could also use `counts.sortByKey()`, for example, to sort the pairs alphabetically, and finally
`counts.collect()` to bring them back to the driver program as an array of objects.

**Note:** when using custom objects as the key in key-value pair operations, you must be sure that a
custom `equals()` method is accompanied with a matching `hashCode()` method. For full details, see
the contract outlined in the [Object.hashCode()
documentation](http://docs.oracle.com/javase/7/docs/api/java/lang/Object.html#hashCode())

</div>

Expand Down