Question

我尝试建立一个项目，找出每月平均温度的最大值。这是我的代码：

文件 Map.java

import java.io.IOException;
import java.util.StringTokenizer;

import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.FloatWritable;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Mapper;

public class Map extends Mapper<LongWritable, Text, Text, FloatWritable> {

    private FloatWritable average = new FloatWritable();
    private float maxFloat, minFloat, averageFloat;
    private Text word = new Text();

    @Override
    protected void map(LongWritable key, Text value, Context context)
            throws IOException, InterruptedException {

        StringTokenizer line = new StringTokenizer(value.toString(), ",");

        if (line.countTokens() > 0) {

            word.set(line.nextToken().substring(2,8));
            if (line.hasMoreTokens()) {
                maxFloat = Float.parseFloat(line.nextToken());
            }
            if (line.hasMoreTokens()) {
                minFloat = Float.parseFloat(line.nextToken());

            }
            averageFloat = (minFloat + maxFloat) / 2;
            average.set(averageFloat);
            context.write(word, average);
        }
    }
}

档案 Reduce.java

import org.apache.hadoop.io.FloatWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Reducer;

import java.io.IOException;
import java.util.Iterator;

public class Reduce extends Reducer<Text, FloatWritable, Text, FloatWritable> {

    private float max_temp = Float.MIN_VALUE;

    private float temp = 0;

    @Override
    protected void reduce(Text key, Iterable<FloatWritable> values, Context context) 
            throws IOException, InterruptedException {
        Iterator<FloatWritable> itr = values.iterator();
        while (itr.hasNext()) {
            temp = itr.next().get();
            if (temp > max_temp) {
                max_temp = temp;
            }
        }
        context.write(key, new FloatWritable(max_temp));
    }

}

档案 MaxTempDriver.java

import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.FloatWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;

public class MaxTempDriver {
    public static void main(String[] args) throws Exception {        

        // Create a new job
        Job job = new Job();

        // Set job name to locate it in the distributed environment
        job.setJarByClass(MaxTempDriver.class);
        job.setJobName("Max Temperature");

        // Set input and output Path, note that we use the default input format
        // which is TextInputFormat (each record is a line of input)
        FileInputFormat.addInputPath(job, new Path(args[0]));
        FileOutputFormat.setOutputPath(job, new Path(args[1]));

        // Set Mapper and Reducer class
        job.setMapperClass(Map.class);
        job.setCombinerClass(Reduce.class);
        job.setReducerClass(Reduce.class);

        // Set Output key and value
        job.setOutputKeyClass(Text.class);
        job.setOutputValueClass(FloatWritable.class);

        System.exit(job.waitForCompletion(true) ? 0 : 1);
    }
}

现在我不知道如何编译这3个文件。我从互联网的一些教程中读到了，但似乎他们在同一个文件中只有map.class和reduce.class的1个文件。如何编译这些文件？

如何编译Java源代码？

0 个答案: