两个mapreduce程序实现不同的功能 而mapreduce1的输出将要作为mapreduce2的输入

example:

JobConf conf1 = new JobConf(YourClass.class);

//set configurations

...

//set inputformat

conf1.setInputFormat(SomeInputFormatExtendsFromInputFormat.class)

conf1.setOutputFormat(SomeOutputFormatExtendsFromOutputFormat.class)

//set input path

FileInputFormat.setInputPaths(conf1, "/your_input_dir");

FileOutputFormat.setOutputPaths(conf1, "/your_first_output_dir");

JobClient.runJob(conf1);

//at this point, the job should have finished. Use submitJob(conf1) to submit it asynchronisely.

JobConf conf2 = new JobConf();

//do the same for conf2, except the input path

FileInputFormat.setInputPaths(conf1, "/your_first_output_dir");

FileOutputFormat.setOutputPaths(conf1, "/your_first_input_dir");

JobClient.runJob(conf);

自己继承InputFormat, OutputFormat来定义合适的分割，读，写文件方式。mapreduce有一些实现好的，比如FileInputFormat, SequenceFileInputFormat。