minecraft-kajetans-mod/src/main/java/me/km/scoreboard/PlayerScoreboard.java

package me.km.scoreboard;

import java.util.HashMap;
import java.util.HashSet;
import net.minecraft.entity.player.EntityPlayerMP;
import net.minecraft.network.play.server.SPacketDisplayObjective;
import net.minecraft.network.play.server.SPacketScoreboardObjective;
import net.minecraft.network.play.server.SPacketUpdateScore;
import net.minecraft.scoreboard.IScoreCriteria;
import net.minecraft.scoreboard.Score;
import net.minecraft.scoreboard.ScoreObjective;
import net.minecraft.scoreboard.Scoreboard;

public class PlayerScoreboard 
{
    private final HashMap<Integer, String> elements;
    private final HashSet<Integer> toRemove;
    private final HashMap<Integer, String> toAdd;
    
    private final Scoreboard board;
    private final ScoreObjective o;
    private boolean changeNeeded;
    
    private final EntityPlayerMP p;

    public PlayerScoreboard(EntityPlayerMP p)
    {
        toRemove = new HashSet<>();
        toAdd = new HashMap<>();
        elements = new HashMap<>();
        changeNeeded = true;
        board = new Scoreboard();
        o = new ScoreObjective(board, "ScoreBoardAPI", IScoreCriteria.DUMMY);
        o.setDisplayName("§6---------------");
        this.p = p;
        p.connection.sendPacket(new SPacketScoreboardObjective(o, 0));
    }
    
    public void addText(int id, String text)
    { 
        String s = elements.get(id);
        if(s != null && !s.equals(text))
        {
            toRemove.add(id);
            toAdd.put(id, text);
            changeNeeded = true;
        }
        else if(s == null)
        {
            toAdd.put(id, text);
            changeNeeded = true;
        }
    }
    
    public void removeText(int id)
    { 
        if(elements.containsKey(id))
        {
            toRemove.add(id);
            changeNeeded = true;
        }
    }
    
    public void clear()
    {
        elements.keySet().forEach(i -> toRemove.add(i));
        update();
    }

    public void update()
    {         
        if(!changeNeeded)
        {
            return;
        }
        
        if(!toRemove.isEmpty())
        {
            toRemove.forEach(i -> 
            {
                String s = elements.remove(i);
                if(s != null)
                {
                    p.connection.sendPacket(new SPacketUpdateScore(s, o));
                }
            });
            toRemove.clear();
        }
        
        if(!toAdd.isEmpty())
        {
            toAdd.entrySet().stream().forEach((e) -> 
            {
                elements.put(e.getKey(), e.getValue());
                Score score = new Score(board, o, e.getValue());
                score.setScorePoints(e.getKey());
                p.connection.sendPacket(new SPacketUpdateScore(score));
            });      
            toAdd.clear();
        }
        
        changeNeeded = false;
        // displaying objective in sidebar
        p.connection.sendPacket(new SPacketDisplayObjective(1, o));
    }
}