arrays - 将Reducer方法的Iterator 对象存储到数组

Question

我要储存
迭代器值
这是Reduce方法的参数，即

public void reduce(IntWritable key, Iterator<Pojo> values,
        OutputCollector<IntWritable, SubArrayWritable> output, Reporter reporter)

在自定义ArrayWritable类对象中，即PojoArrayWritable对象。
我已经创建了PojoArrayWritable类，并且该代码是

import java.io.DataInput;
import java.io.DataOutput;
import java.io.IOException;
import org.apache.hadoop.io.ArrayWritable;
import org.apache.hadoop.io.DoubleWritable;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.Writable;
import org.apache.hadoop.io.WritableComparable;

public class SubArrayWritable extends ArrayWritable
{
public SubArrayWritable() {
    super(Sub.class);
}
public SubArrayWritable(Sub[] values) {
    super(Sub.class, values);
}
}

并且Sub.class具有以下代码-

import java.io.DataInput;
import java.io.DataOutput;
import java.io.IOException;
import org.apache.hadoop.io.DoubleWritable;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.Writable;

public class Sub implements Writable {
private IntWritable id = new IntWritable();
private LongWritable pno = new LongWritable();
private DoubleWritable sal = new DoubleWritable();

public IntWritable getid() {
    return id;
}

public void setId(IntWritable id) {
    this.id = id;
}

public LongWritable getPno() {
    return pno;
}

public void setPno(LongWritable pno) {
    this.pno = pno;
}

public DoubleWritable getSal() {
    return sal;
}

public void setSal(DoubleWritable sal) {
    this.sal = sal;
}

@Override
public void readFields(DataInput in) throws IOException {
    id.readFields(in);
    pno.readFields(in);
    sal.readFields(in);

}

@Override
public void write(DataOutput out) throws IOException {
    id.write(out);
    pno.write(out);
    sal.write(out);
}


}

而在Reducer类中

public void reduce(IntWritable key, Iterator<Pojo> values,
        OutputCollector<IntWritable, SubArrayWritable> output, Reporter reporter)

我想将Iterator的values对象存储到数组中，即存储到SubArrayWritable的对象中，所以我该怎么做，因为我不知道Iterator的values对象的大小/长度，所以我将创建的SubArrayWritable对象的长度是多少？ ??

所以最后基本上我有了 Iterator<Pojo> values，我必须将其转换为 array of Pojo

Answer 1

我为此找到了解决方案-

    Pojo pojo=new Pojo();
    List<Pojo> list=new ArrayList<Pojo>();

    if (values.hasNext()) {
        pojo = values.next();
        list.add(pojo);
       }

现在我可以使用包含迭代器对象值的pojo对象值