How can I get the output?

I can’t find the way to get the output from the container

public static void main(String[] args) throws InterruptedException {
        DockerClient docker = DockerClientBuilder
            .getInstance("tcp://127.0.0.1:2376")
            .build();

        // Run
        CreateContainerResponse container = docker
            .createContainerCmd("ubuntu")
            .withCmd("/bin/sh", "-c", "echo Hello world!")
            .withTty(true)
            .exec();

        // Log
        LogContainerResultCallback loggingCallback = new
            LogContainerResultCallback();

        docker
            .logContainerCmd(container.getId())
            .withStdErr(true)
            .withStdOut(true)
            .withFollowStream(true)
            .withTailAll()
            .exec(loggingCallback)
            .awaitStarted();

        loggingCallback.awaitCompletion(3, TimeUnit.SECONDS);

        String output = loggingCallback.toString();
        System.out.println(output);
    }

[LeslieMurphy]

This works for me:

public class GetContainerLog {
	private DockerClient dockerClient;
	private String containerId;
	private int lastLogTime;
	
	private static String nameOfLogger = "dockertest.PrintContainerLog";
	private static Logger myLogger = Logger.getLogger(nameOfLogger);
	
	public GetContainerLog(DockerClient dockerClient, String containerId) {
		this.dockerClient = dockerClient;
		this.containerId = containerId;
		this.lastLogTime = (int) (System.currentTimeMillis() / 1000);
	}
	
	public List<String> getDockerLogs() {

	    final List<String> logs = new ArrayList<>();
	    
	   LogContainerCmd logContainerCmd = dockerClient.logContainerCmd(containerId);
	    logContainerCmd.withStdOut(true).withStdErr(true);
	    logContainerCmd.withSince( lastLogTime );  // UNIX timestamp (integer) to filter logs. Specifying a timestamp will only output log-entries since that timestamp. 
	    // logContainerCmd.withTail(4);  // get only the last 4 log entries
	    
	    logContainerCmd.withTimestamps(true);
	    
	    try {
	        logContainerCmd.exec(new LogContainerResultCallback() {
	            @Override
	            public void onNext(Frame item) {
	                logs.add(item.toString());
	            }
	        }).awaitCompletion();
	    } catch (InterruptedException e) {
	    	myLogger.severe("Interrupted Exception!" + e.getMessage());
	    }

	    lastLogTime = (int) (System.currentTimeMillis() / 1000) + 5;  // assumes at least a 5 second wait between calls to getDockerLogs
	    
	    return logs;
	}

[bsideup]

@ketansgaikwad05 see the note: https://github.com/docker-java/docker-java/blob/e01dd42d4041870147163dc78323bfc94b51bb57/docker-java-core/src/main/java/com/github/dockerjava/core/command/LogContainerResultCallback.java#L16