Hadoop WordCount Tutorial java.lang.ClassNotFoundException

I'm relatively new to hadoop and I'm struggling a little bit to understand the ClassNotFoundException I get when trying to run the job. I'm using the standard tutorial found here and here is my WordCount class (running on ubuntu 16.04 hadoop 2.7.3 distributed cluster mode):

import java.io.IOException;
import java.util.StringTokenizer;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.Mapper;
import org.apache.hadoop.mapreduce.Reducer;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;

public class WordCount {

  public static class TokenizerMapper
       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);
      }
    }
  }

  public static class IntSumReducer
       extends Reducer<Text,IntWritable,Text,IntWritable> {
    private IntWritable result = new IntWritable();

    public void reduce(Text key, Iterable<IntWritable> values,
                       Context context
                       ) throws IOException, InterruptedException {
      int sum = 0;
      for (IntWritable val : values) {
        sum += val.get();
      }
      result.set(sum);
      context.write(key, result);
    }
  }

  public static void main(String[] args) throws Exception {
    Configuration conf = new Configuration();
    Job job = Job.getInstance(conf, "word count");
    job.setJarByClass(WordCount.class);
    job.setMapperClass(TokenizerMapper.class);
    job.setCombinerClass(IntSumReducer.class);
    job.setReducerClass(IntSumReducer.class);
    job.setOutputKeyClass(Text.class);
    job.setOutputValueClass(IntWritable.class);
    FileInputFormat.addInputPath(job, new Path(args[0]));
    FileOutputFormat.setOutputPath(job, new Path(args[1]));
    System.exit(job.waitForCompletion(true) ? 0 : 1);
  }
}

To try and remain organized, I added a couple paths to my ~/.bashrc file:

hduser@mynode:~$ cd $HADOOP_CODE
hduser@mynode:/usr/local/hadoop/code$

This is one directory down from the $HADOOP_HOME directory. To compile the WordCount.JAVA file, I ran:

hduser@mynode:/usr/local/hadoop$ hadoop com.sun.tools.javac.Main $HADOOP_CODE/WordCount.java
hduser@mynode:/usr/local/hadoop$ jar cf wc.jar $HADOOP_CODE/WordCount*.class

I then tried:

hduser@mynode:/usr/local/hadoop$ hadoop jar $HADOOP_CODE/wc.jar $HADOOP_CODE/WordCount /home/hduser/input /home/hduser/output/wordcount

which bombed with the following error:

Exception in thread "main" java.lang.ClassNotFoundException: /usr/local/hadoop/code/WordCount

EDIT This gave me the same error:

hduser@mynode:/usr/local/hadoop/code$ hadoop jar $HADOOP_CODE/wc.jar WordCount /home/hduser/input /home/hduser/output/wordcount

To get it to run without error, I moved the WordCount.Java file up one directory to the default hadoop ($HADOOP_HOME) folder. I also know from here and here that the solution is to add a package to the file.

What I'm trying to understand is why that is the solution. With no package name, where is hadoop looking for the specified package, and why can't I pass it a full path to get it to run correctly? This may be a basic java question (apologies - I'm from the python world), but what is the package name doing during the compile process that makes it so I could run without a path name, but leaving off the package name means it has to be in that default directory? I'd prefer not to have to add a package name to every job I run. An explanation would be greatly appreciated!