import org.mozilla.taskcluster.client.*;
import org.mozilla.taskcluster.client.queue.*;

...

	// Create credentials, e.g. from environment variables...
    Credentials creds = new Credentials(
        System.getenv("TASKCLUSTER_CLIENT_ID"),
        System.getenv("TASKCLUSTER_ACCESS_TOKEN"),
        System.getenv("TASKCLUSTER_CERTIFICATE")
    );

    // Instantiate the Queue client class
    Queue queue = new Queue(creds);

    // Supply a unique task name
    String taskId = "...";

    // Define the task
    TaskDefinition td = new TaskDefinition();

    // Set properties, as required...
    td.created = new java.util.Date();
    td.provisionerId = "...";
    td.routes = new String[] { "...", "...", "..." };
    td.XYZ = ...

    // Execute the API call
    try {
        TaskStatusResponse tsr = queue.defineTask(taskId, td).responsePayload;

        // Process API response
        System.out.println("State is " + tsr.status.state);

    } catch (APICallFailure e) {
        // handle exception ...
    }

...

package org.mozilla.taskcluster;

import java.util.Date;

import org.mozilla.taskcluster.client.APICallFailure;
import org.mozilla.taskcluster.client.CallSummary;
import org.mozilla.taskcluster.client.Credentials;
import org.mozilla.taskcluster.client.EmptyPayload;
import org.mozilla.taskcluster.client.InvalidOptionsException;
import org.mozilla.taskcluster.client.queue.ListArtifactsResponse;
import org.mozilla.taskcluster.client.queue.ListArtifactsResponse.Artifacts;
import org.mozilla.taskcluster.client.queue.Queue;

/**
 * This simple demo lists the artifacts in run 0 of task U7On2dUVS9KlEgw7LUaCMQ.
 * It creates permanent credentials from environment variables
 * TASKCLUSTER_CLIENT_ID and TASKCLUSTER_ACCESS_TOKEN, and then creates
 * temporary credentials, valid for 24 hours, from these permanent credentials.
 * It queries the Queue using the temporary credentials, and with limited
 * authorized scopes.
 *
 * Note, the queue.listArtifacts(...) call doesn't require any scopes, the
 * generation of temporary credentials, and limiting via authorized scopes is
 * purely illustrative. The TASKCLUSTER_CLIENT_ID must satisfy
 * auth:create-client:demo-client/taskcluster-client-java, though.
 */
public class Demo {
    public static void main(String[] args) {
        Credentials permCreds = new Credentials(
            System.getenv("TASKCLUSTER_CLIENT_ID"),
            System.getenv("TASKCLUSTER_ACCESS_TOKEN")
        );
        Date now = new Date();
        try {
            Credentials tempCreds = permCreds.createTemporaryCredentials(
                "demo-client/taskcluster-client-java",
                new String[] {
                    "assume:legacy-permacred"
                },
                // valid immediately
                now,
                // expire in 24 hours
                new Date(now.getTime() + 1000 * 60 * 60 * 24)
            );
            tempCreds.authorizedScopes = new String[] { "queue:get-artifact:private/build/*" };
            Queue queue = new Queue(tempCreds);
            CallSummary<EmptyPayload, ListArtifactsResponse> cs = queue.listArtifacts("U7On2dUVS9KlEgw7LUaCMQ", "0");
            ListArtifactsResponse artifacts = cs.responsePayload;
            System.out.println("Artifacts:");
            for (Artifacts artifact : artifacts.artifacts) {
                System.out.println("  * " + artifact.name);
            }
            System.out.println("Done.");
        } catch (InvalidOptionsException e) {
            System.err.println("Could not create temporary credentials");
            e.printStackTrace();
        } catch (APICallFailure e) {
            System.err.println("Could not query the Queue service");
            e.printStackTrace();
        }
    }
}