Java tutorial
/* Copyright (c) 2015, Yiju Wei. HAMR is a Frame let you use annotations to describe and execute a MapReduce process. This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; version 2 of the License. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA */ package hamr.core.general.counter; import java.lang.reflect.Field; import java.util.Map; import java.util.Set; import org.apache.hadoop.mapreduce.Reducer.Context; import hamr.core.general.annotations.TargetField; import hamr.core.general.bean.AnnotedBean; public class SumCounter extends Counter { private Integer count; @SuppressWarnings("rawtypes") public SumCounter(Context context) { super(context); count = 0; } public void count(AnnotedBean key) { count += 1; } public boolean end(AnnotedBean ret) { if (ret == null) { return false; } Map<Field, TargetField> targets = getTargetFields(ret); Set<Field> keys = targets.keySet(); for (Field f : keys) { try { f.set(ret, count); } catch (IllegalArgumentException | IllegalAccessException e) { e.printStackTrace(); } } return true; } }