1、定义计数器

        1)枚举声明计数器

Context context...//自定义枚举变量EnumCounter counter = context.getCounter(Enum enum)

        2)自定义计数器

Context context...//自己命名groupName和counterNameCounter counter = context.getCounter(String groupName,String counterName)

2、为计数器赋值

        1)初始化计数器

counter.setValue(long value);//设置初始值

        2)计数器自增

counter.increment(long incr);//增加计数

3、获取计数器的值

        1) 获取枚举计数器的值

Job job...job.waitForCompletion(true);Counters counters=job.getCounters();Counter counter=counters.findCounter("BAD_RECORDS");//查找枚举计数器，假如Enum的变量为BAD_RECORDSlong value=counter.getValue();//获取计数值

        2) 获取自定义计数器的值

Job job...job.waitForCompletion(true);Counters counters=job.getCounters();Counter counter=counters.findCounter("ErrorCounter","toolong");//假如groupName为ErrorCounter，counterName为toolonglong value=counter.getValue();//获取计数值

        3) 获取内置计数器的值

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Job job...job.waitForCompletion(true);Counters counters=job.getCounters();//查找作业运行启动的reduce个数的计数器，groupName和counterName可以从内置计数器表格查询（前面已经列举有）Counter counter=counters.findCounter("org.apache.hadoop.mapreduce.JobCounter","TOTAL_LAUNCHED_REDUCES");//假如groupName为org.apache.hadoop.mapreduce.JobCounter，counterName为TOTAL_LAUNCHED_REDUCESlong value=counter.getValue();//获取计数值

        4) 获取所有计数器的值

Counters counters = job.getCounters();for (CounterGroup group : counters) {    for (Counter counter : group) {            System.out.println(counter.getDisplayName() + ": " + counter.getName() + ": "+ counter.getValue());        } }