Guide to arraywritable use in MapReduce _java

When you write a mapreduce program, the data that is passed between map and reduce needs to be ArrayList type, and you encounter one of these errors during debugging run:

Java.lang.runtimeexception:java.lang.nosuchmethodexception:org.apache.hadoop.io.arraywritable.<init> ()

After querying the official website API document to discover such a passage:

A writable for arrays containing instances of a class. The elements of this writable must all is instances of the same class. If This writable'll be is the input for a reducer, you'll need to create a subclass that sets the value of the prop ER type.  For Example:public class Intarraywritable extends Arraywritable {public intarraywritable () {super (intwritable.class);} }

The original is to implement a arraywritable class of derived classes, when used as long as the implementation of two constructors can

public static class Textarraywritable extends Arraywritable {public
 textarraywritable () {
 super (Text.class); c3/>} public
 
 textarraywritable (string[] strings) {
 super (text.class);
 text[] Texts = new Text[strings.length];
 for (int i = 0; i < strings.length i++) {
 texts[i] = new Text (strings[i));
 Set (texts);
 }