MyApplicationMaster.java
  ...

    // Configuration
    private Configuration conf;

    public MyApplicationMaster() {
    // Set up the configuration
      conf = new YarnConfiguration();
    }

  ...

  MyApplicationMaster.java
  ...

    // Application Attempt Id ( combination of attemptId and fail count )
    protected ApplicationAttemptId appAttemptID;

    // No. of containers to run shell command on
    private int numTotalContainers = 1;

    // Memory to request for the container on which the shell command will run
    private int containerMemory = 10;

    // VirtualCores to request for the container on which the shell command will run
    private int containerVirtualCores = 1;

    // Priority of the request
    private int requestPriority;

    // Location of shell script ( obtained from info set in env )
    // Shell script path in fs
    private String appJarPath = "";
    // Timestamp needed for creating a local resource
    private long appJarTimestamp = 0;
    // File length needed for local resource
    private long appJarPathLen = 0;

  ...

  MyApplicationMaster.java
  ...

    @SuppressWarnings({"unchecked"})
    public void run() throws Exception {
      LOG.info("Running MyApplicationMaster");

      // Initialize clients to ResourceManager and NodeManagers
      AMRMClient<ContainerRequest> amRMClient = AMRMClient.createAMRMClient();
      amRMClient.init(conf);
      amRMClient.start();

      // Register with ResourceManager
      amRMClient.registerApplicationMaster("", 0, "");

      // Set up resource type requirements for Container
      Resource capability = Records.newRecord(Resource.class);
      capability.setMemory(containerMemory);
      capability.setVirtualCores(containerVirtualCores);

      // Priority for worker containers - priorities are intra-application
      Priority priority = Records.newRecord(Priority.class);
      priority.setPriority(requestPriority);

      // Make container requests to ResourceManager
      for (int i = 0; i < numTotalContainers; ++i) {
        ContainerRequest containerAsk = new ContainerRequest(capability, null, null, priority);
        amRMClient.addContainerRequest(containerAsk);
      }


      NMClient nmClient = NMClient.createNMClient();
      nmClient.init(conf);
      nmClient.start();

      // Setup CLASSPATH for Container
      Map<String, String> containerEnv = new HashMap<String, String>();
      containerEnv.put("CLASSPATH", "./*");

      // Setup ApplicationMaster jar file for Container
      LocalResource appMasterJar = createAppMasterJar();

      // Obtain allocated containers and launch
      int allocatedContainers = 0;
      // We need to start counting completed containers while still allocating
      // them since initial ones may complete while we're allocating subsequent
      // containers and if we miss those notifications, we'll never see them again
      // and this ApplicationMaster will hang indefinitely.
      int completedContainers = 0;
      while (allocatedContainers < numTotalContainers) {
        AllocateResponse response = amRMClient.allocate(0);
        for (Container container : response.getAllocatedContainers()) {
          allocatedContainers++;

          ContainerLaunchContext appContainer = createContainerLaunchContext(appMasterJar, containerEnv);
          LOG.info("Launching container " + allocatedContainers);

          nmClient.startContainer(container, appContainer);
        }
        for (ContainerStatus status : response.getCompletedContainersStatuses()) {
          ++completedContainers;
          LOG.info("ContainerID:" + status.getContainerId() + ", state:" + status.getState().name());
        }
        Thread.sleep(100);
      }

      // Now wait for the remaining containers to complete
      while (completedContainers < numTotalContainers) {
        AllocateResponse response = amRMClient.allocate(completedContainers / numTotalContainers);
        for (ContainerStatus status : response.getCompletedContainersStatuses()) {
          ++completedContainers;
          LOG.info("ContainerID:" + status.getContainerId() + ", state:" + status.getState().name());
        }
        Thread.sleep(100);
      }

      LOG.info("Completed containers:" + completedContainers);

      // Un-register with ResourceManager
      amRMClient.unregisterApplicationMaster(
          FinalApplicationStatus.SUCCEEDED, "", "");
      LOG.info("Finished MyApplicationMaster");
    }

  ...

  MyApplicationMaster.java
  ...

  public static void main(String[] args) throws Exception {
    try {
      MyApplicationMaster appMaster = new MyApplicationMaster();
      LOG.info("Initializing MyApplicationMaster");
      boolean doRun = appMaster.init(args);
      if (!doRun) {
        System.exit(0);
      }
      appMaster.run();
    } catch (Throwable t) {
      LOG.fatal("Error running MyApplicationMaster", t);
      LogManager.shutdown();
      ExitUtil.terminate(1, t);
    }
  }

  HelloYarn.java

    public class HelloYarn {
      private static final long MEGABYTE = 1024L * 1024L;

      public HelloYarn() {
        System.out.println("HelloYarn!");
      }

      public static long bytesToMegabytes(long bytes) {
        return bytes / MEGABYTE;
      }

      public void printMemoryStats() {
        long freeMemory = bytesToMegabytes(Runtime.getRuntime().freeMemory());
        long totalMemory = bytesToMegabytes(Runtime.getRuntime().totalMemory());
        long maxMemory = bytesToMegabytes(Runtime.getRuntime().maxMemory());

        System.out.println("The amount of free memory in the Java Virtual Machine: " + freeMemory);
        System.out.println("The total amount of memory in the Java virtual machine: " + totalMemory);
        System.out.println("The maximum amount of memory that the Java virtual machine: " + maxMemory);
      }

      public static void main(String[] args) {
        HelloYarn helloYarn = new HelloYarn();
        helloYarn.printMemoryStats();
      }
    }