Conventions

In this book, you will find a number of styles of text that distinguish between different kinds of information. Here are some examples of these styles, and an explanation of their meaning.

Code words in text, database table names, folder names, filenames, file extensions, pathnames, dummy URLs, user input, and Twitter handles are shown as follows: "The Map() function works on the distributed data and runs the required functionality in parallel."

A block of code is set as follows:

public static class VowelMapper extends Mapper<Object, Text, Text, IntWritable>
{
private final static IntWritable one = new IntWritable(1);
private Text word = new Text();
public void map(Object key, Text value, Context context) throws IOException, InterruptedException
{
StringTokenizer itr = new StringTokenizer(value.toString());
while (itr.hasMoreTokens())
{
word.set(itr.nextToken());
context.write(word, one);
}
}

Any command-line input or output is written as follows:

$ hadoop-daemon.sh start namenode

Note

Warnings or important notes appear in a box like this.

Tip

Tips and tricks appear like this.