[Nutch]编译hadoop出现object[]无法转换为K[]问题解决

1. 问题描述

在使用JDK8编译hadoop 1.2.1的时候会出现object[]无法转换为K[]的问题，如下：

2. 问题解决

（1）打开hadoop目录下的InputSampler.java文件，路径如下：
hadoop-1.2.1\src\mapred\org\apache\hadoop\mapreduce\lib\partition\InputSampler.java

（2）大概319行找到如下内容：

    final InputFormat inf = 
        ReflectionUtils.newInstance(job.getInputFormatClass(), conf);
    int numPartitions = job.getNumReduceTasks();
    K[] samples = sampler.getSample(inf, job);
    LOG.info("Using " + samples.length + " samples");
    RawComparator<K> comparator =
      (RawComparator<K>) job.getSortComparator();

将其修改为：

    final InputFormat inf = 
        ReflectionUtils.newInstance(job.getInputFormatClass(), conf);
    int numPartitions = job.getNumReduceTasks();
    K[] samples = (K[])sampler.getSample(inf, job);
    LOG.info("Using " + samples.length + " samples");
    RawComparator<K> comparator =
      (RawComparator<K>) job.getSortComparator();

如下图：

3. 重新编译