Could not find or load main class org.apache.hadoop.mapreduce.v2.app.MRAppMaster

I had the same problem and resolved by adding this in mapred-site.xml (so edit your mapreduce.application.classpath property)

<property> 
    <name>mapreduce.application.classpath</name>
    <value>$HADOOP_MAPRED_HOME/share/hadoop/mapreduce/*,$HADOOP_MAPRED_HOME/share/hadoop/mapreduce/lib/*,$HADOOP_MAPRED_HOME/share/hadoop/common/*,$HADOOP_MAPRED_HOME/share/hadoop/common/lib/*,$HADOOP_MAPRED_HOME/share/hadoop/yarn/*,$HADOOP_MAPRED_HOME/share/hadoop/yarn/lib/*,$HADOOP_MAPRED_HOME/share/hadoop/hdfs/*,$HADOOP_MAPRED_HOME/share/hadoop/hdfs/lib/*</value>
</property>

Just edit the mapred-site.xml file :

Add following properties:

1. <property> <name>mapreduce.framework.name</name> <value>yarn</value> </property>

2. <property> <name>yarn.app.mapreduce.am.env</name> <value>HADOOP_MAPRED_HOME=/Users/adityaatri/Applications/hadoop-3.1.3</value> </property>

3. <property> <name>mapreduce.map.env</name> <value>HADOOP_MAPRED_HOME=/Users/adityaatri/Applications/hadoop-3.1.3</value> </property>

4. <property> <name>mapreduce.reduce.env</name> <value>HADOOP_MAPRED_HOME=/Users/adityaatri/Applications/hadoop-3.1.3</value> </property>

Now for all the above 4 properties, replace the path /Users/adityaatri/Applications/hadoop-3.1.3 with your Hadoop Home Address.

Now add the 5th property :

5. <property> <name>mapreduce.application.classpath</name> <value></value> </property>

The <value> element must be filled with content after executing below commands in your terminal :

1. export HADOOP_CLASSPATH=$(hadoop classpath)

2. echo $HADOOP_CLASSPATH

The output from my terminal :

/Users/adityaatri/Applications/hadoop-3.1.3/etc/hadoop:/Users/adityaatri/Applications/hadoop-3.1.3/share/hadoop/common/lib/*:/Users/adityaatri/Applications/hadoop-3.1.3/share/hadoop/common/*:/Users/adityaatri/Applications/hadoop-3.1.3/share/hadoop/hdfs:/Users/adityaatri/Applications/hadoop-3.1.3/share/hadoop/hdfs/lib/*:/Users/adityaatri/Applications/hadoop-3.1.3/share/hadoop/hdfs/*:/Users/adityaatri/Applications/hadoop-3.1.3/share/hadoop/mapreduce/lib/*:/Users/adityaatri/Applications/hadoop-3.1.3/share/hadoop/mapreduce/*:/Users/adityaatri/Applications/hadoop-3.1.3/share/hadoop/yarn:/Users/adityaatri/Applications/hadoop-3.1.3/share/hadoop/yarn/lib/*:/Users/adityaatri/Applications/hadoop-3.1.3/share/hadoop/yarn/*

Copy this content inside the <value> element of the 5th property.

Now you will not get any error. :)