Hadoop java.lang.NoSuchMethodException: WordCountHello$WCMapper.<init>()

问题：

java.lang.Exception: java.lang.RuntimeException: java.lang.NoSuchMethodException: WordCountHello$WCMapper.<init>()
	at org.apache.hadoop.mapred.LocalJobRunner$Job.runTasks(LocalJobRunner.java:462)
	at org.apache.hadoop.mapred.LocalJobRunner$Job.run(LocalJobRunner.java:522)
Caused by: java.lang.RuntimeException: java.lang.NoSuchMethodException: WordCountHello$WCMapper.<init>()
	at org.apache.hadoop.util.ReflectionUtils.newInstance(ReflectionUtils.java:134)
	at org.apache.hadoop.mapred.MapTask.runNewMapper(MapTask.java:747)
	at org.apache.hadoop.mapred.MapTask.run(MapTask.java:341)
	at org.apache.hadoop.mapred.LocalJobRunner$Job$MapTaskRunnable.run(LocalJobRunner.java:243)
	at java.util.concurrent.Executors$RunnableAdapter.call(Unknown Source)
	at java.util.concurrent.FutureTask.run(Unknown Source)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
	at java.lang.Thread.run(Unknown Source)
Caused by: java.lang.NoSuchMethodException: WordCountHello$WCMapper.<init>()
	at java.lang.Class.getConstructor0(Unknown Source)
	at java.lang.Class.getDeclaredConstructor(Unknown Source)
	at org.apache.hadoop.util.ReflectionUtils.newInstance(ReflectionUtils.java:128)

解决：

因为内部类未初始化，执行错误，可以使用static修饰类，这样在执行之前先初始化内部类