Solved How to register an new effect!

[FilipeNock]

Example:

    public void Sound(String s, Player p) {
        p.playSound(p.getLocation(), Sound.valueOf(s), 1, 1);
    
    }

Skript.registerEffect(TestSound.class, "play test [sound] %string% to %player%");

I really do not understand how to do this! And I've been looking for something else I could not understand

Someone is opposed to helping me?
Please, I'm asking for help so I beg you not to insult me

EDIT: Attempts

package me.filipenock.ponte;

import org.bukkit.Sound;
import org.bukkit.entity.Player;
import org.bukkit.event.Event;
import org.eclipse.jdt.annotation.Nullable;

import ch.njol.skript.lang.Effect;
import ch.njol.skript.lang.Expression;
import ch.njol.skript.lang.SkriptParser.ParseResult;
import ch.njol.util.Kleenean;

public class TestSound extends Effect{
  
    private Expression<String> sound;
    private Expression<Player> player;

    @SuppressWarnings("unchecked")
    @Override
    public boolean init(Expression<?>[] var, int arg1, Kleenean param, ParseResult ParseResult) {
        this.sound = (Expression<String>) var[0];
        this.player = (Expression<Player>) var[1];
        return true;
    }

    @Override
    public String toString(@Nullable Event arg0, boolean arg1) {
        return null;
    }

    @Override
    protected void execute(Event e) {
        ((Player) player).playSound(((Player)this.player.getSingle(e)).getLocation(), Sound.valueOf(((String)this.sound.getSingle(e))), 1, 1);
      
    }

}

Result:

java.lang.ClassCastException: ch.njol.skript.expressions.ExprEntity cannot be cast to org.bukkit.entity.Player

 

[ShaneBee]

To get the value of an expression, use Expression#getSingle(Event) or Expression#getAll(Event) instead of casting. Note, getSingle may return null, so you should return early if the expression may not be null.

public class TestSound extends Effect {
  static {
    Skript.registerEffect(TestSound.class, "play test [sound] %string% to %player%");
  }
 
  private Expression<String> sound;
  private Expression<Player> player;

  @Override
  protected void execute(Event e) {
    String s = sound.getSingle(e);
    Player p = player.getSingle(e);
   
    if (s == null || p == null) {
      return null;
    }

    // do whatever
  }

  @Override
  public String toString(@Nullable Event e, boolean debug) {
    return "this string is displayed for debug purposes; you should change it!";
  }

  @SuppressWarnings("unchecked")
  @Override
  public boolean init(Expression<?>[] exprs, int matchedPattern, Kleenean isDelayed, SkriptParser.ParseResult parseResult) {
    sound = (Expression<String>) exprs[0];
    player = (Expression<Player>) exprs[1];
    return true;
  }
}

Since it looks like you're a new developer, you should read the Skript Addon Best Practices and check out the source code of other addons for examples.