Expanding your code

Before testing, let's improve on the onEnable() method by implementing an if statement. If there is only one player online then why not say hello to that specific player? We can get an array of all the players that are online by calling Bukkit.getOnlinePlayers(), if we wish to check if the length of the array is equal to 1, we can accomplish this with an if/else statement. This is shown in the following code:

if (Bukkit.getOnlinePlayers().length == 1) {//Only 1 player online
  //Say 'Hello' to the specific player
} else {
  //Say 'Hello' to the Minecraft World
  broadcastToServer("Hello World!");
}

Within our if statement, we will now get the first and only object in the player array. Once we have that, we can continue by broadcasting Hello along with the player's name. After completing the if statement your entire class will look as shown in the following code:

package com.codisimus.myfirstbukkitplugin;

 importorg.bukkit.Bukkit;
 importorg.bukkit.entity.Player;
 importorg...