## org.apache.hadoop.mapred.lib.aggregate
Class UniqValueCount

    java.lang.Object
      org.apache.hadoop.mapred.lib.aggregate.UniqValueCount

All Implemented Interfaces:
  ValueAggregator

    public class UniqValueCount

extends Object
implements ValueAggregator

This class implements a value aggregator that dedupes a sequence of objects.

Constructor Summary
`UniqValueCount()` the default constructor
`UniqValueCount(long maxNum)` constructor

Method Summary
`void` `addNextValue(Object val)` add a value to the aggregator
`ArrayList` `getCombinerOutput()`
`String` `getReport()`
`Set` `getUniqueItems()`
`void` `reset()` reset the aggregator
`long` `setMaxItems(long n)` Set the limit on the number of unique values

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Constructor Detail

### UniqValueCount

    public UniqValueCount()

  the default constructor

### UniqValueCount

    public UniqValueCount(long maxNum)

  constructor

  Parameters:
    `maxNum` - the limit in the number of unique values to keep.

Method Detail

### setMaxItems

    public long setMaxItems(long n)

  Set the limit on the number of unique values

  Parameters:
    `n` - the desired limit on the number of unique values
  Returns:
    the new limit on the number of unique values

### addNextValue

    public void addNextValue(Object val)

  add a value to the aggregator

  Specified by:
    `addNextValue` in interface `ValueAggregator`
  Parameters:
    `val` - an object.

### getReport

    public String getReport()

  Specified by:
    `getReport` in interface `ValueAggregator`
  Returns:
    return the number of unique objects aggregated

### getUniqueItems

    public Set getUniqueItems()

  Returns:
    the set of the unique objects

### reset

    public void reset()

  reset the aggregator

  Specified by:
    `reset` in interface `ValueAggregator`

### getCombinerOutput

    public ArrayList getCombinerOutput()

  Specified by:
    `getCombinerOutput` in interface `ValueAggregator`
  Returns:
    return an array of the unique objects. The return value is expected to be used by the a combiner.

Copyright © 2009 The Apache Software Foundation