@Bin Xiong : I think you are working on sandbox 2.x. In 2.x examples.jar files are located in the following location : execute the command “find / -xdev -name hadoop-mapreduce-examples-*.jar”
Finally run example using below command :
hadoop jar /usr/hdp/2.3.2.0-2950/hadoop-mapreduce/hadoop-mapreduce-examples-*.jar pi 10 10.