ActionBar

ActionBarMessage.java

package li.angu.youtube.tutorial.actionbar;

import net.minecraft.server.v1_8_R3.IChatBaseComponent;
import net.minecraft.server.v1_8_R3.PacketPlayOutChat;
import org.bukkit.ChatColor;
import org.bukkit.craftbukkit.v1_8_R3.entity.CraftPlayer;
import org.bukkit.entity.Player;

/**
 * Created by finreinhard on 04.01.17.
 */
public class ActionBarMessage {

    private String message;

    public ActionBarMessage(String message) {
        this.message = message;
    }

    public String getMessage() {
        return message;
    }

    public void setMessage(String message) {
        this.message = message;
    }

    public void send(Player player) {
        /*
        BYTE
        0 = Chat Message
        1 = System Message
        2 = Action Bar
         */
        PacketPlayOutChat packet =
                new PacketPlayOutChat(IChatBaseComponent.ChatSerializer.a("{'text': '" + ChatColor
                        .translateAlternateColorCodes('&', getMessage()) + "'}"), (byte) 2);

        ((CraftPlayer) player).getHandle().playerConnection.sendPacket(packet);
    }
}

TestCommand.java

package li.angu.youtube.tutorial.command;

import li.angu.youtube.tutorial.actionbar.ActionBarMessage;
import org.bukkit.command.Command;
import org.bukkit.command.CommandExecutor;
import org.bukkit.command.CommandSender;
import org.bukkit.entity.Player;

import java.util.Arrays;

/**
 * Created by finreinhard on 04.01.17.
 */
public class TestCommand implements CommandExecutor {

    @Override public boolean onCommand(CommandSender sender, Command command, String label, String[] arguments) {
        if (!(sender instanceof Player)) {
            sender.sendMessage("Du hast keine Actionbar!");
            return false;
        }

        String testMessage = "&8Das ist eine &6Test Nachricht&8!";

        // /test &6Das ist auch eine &3Test Nachricht
        // Das ist auch eine Test Nachricht
        if (arguments.length != 0) {

            // JAVA 8
            StringBuilder stringBuilder = new StringBuilder();
            Arrays.stream(arguments).forEach(argument -> stringBuilder.append(argument).append(" "));
            testMessage = stringBuilder.toString();

            // JAVA 7 & 6
            /*
            testMessage = "";
            for (String argument : arguments) {
                testMessage += argument + " ";
            }
            */
        }

        new ActionBarMessage(testMessage).send((Player) sender);

        return true;
    }
}