ExperienceManager.java

package me.dizmizzer.xpshop;


import java.math.BigDecimal;
import org.bukkit.entity.Player;

public class ExperienceManager {


   public ExperienceManager() {
   }

   public int getTotalExperience(Player player) {
     int experience = 0;
     int level = player.getLevel();
     if(level >= 0 && level <= 15) {
      experience = (int) Math.ceil(Math.pow(level, 2) + (6 * level));
      int requiredExperience = 2 * level + 7;
      double currentExp = Double.parseDouble(Float.toString(player.getExp()));
      experience += Math.ceil(currentExp * requiredExperience);
      return experience;
     } else if(level > 15 && level <= 30) {
       experience = (int) Math.ceil((2.5 * Math.pow(level, 2) - (40.5 * level) + 360));
       int requiredExperience = 5 * level - 38;
       double currentExp = Double.parseDouble(Float.toString(player.getExp()));
       experience += Math.ceil(currentExp * requiredExperience);
       return experience;
     } else {
       experience = (int) Math.ceil(((4.5 * Math.pow(level, 2) - (162.5 * level) + 2220)));
       int requiredExperience = 9 * level - 158;
       double currentExp = Double.parseDouble(Float.toString(player.getExp()));
       experience += Math.ceil(currentExp * requiredExperience);
       return experience;
     }
   }

   public void setTotalExperience(Player player, int xp) {
     //Levels 0 through 15
     if(xp >= 0 && xp < 351) {
       //Calculate Everything
       int a = 1; int b = 6; int c = -xp;
       int level = (int) (-b + Math.sqrt(Math.pow(b, 2) - (4 * a * c))) / (2 * a);
       int xpForLevel = (int) (Math.pow(level, 2) + (6 * level));
       int remainder = xp - xpForLevel;
       int experienceNeeded = (2 * level) + 7;
       float experience = (float) remainder / (float) experienceNeeded;
       experience = round(experience, 2);

       //Set Everything
       player.setLevel(level);
       player.setExp(experience);
     //Levels 16 through 30
     } else if(xp >= 352 && xp < 1507) {
       //Calculate Everything
       double a = 2.5; double b = -40.5; int c = -xp + 360;
       double dLevel = (-b + Math.sqrt(Math.pow(b, 2) - (4 * a * c))) / (2 * a);
       int level = (int) Math.floor(dLevel);
       int xpForLevel = (int) (2.5 * Math.pow(level, 2) - (40.5 * level) + 360);
       int remainder = xp - xpForLevel;
       int experienceNeeded = (5 * level) - 38;
       float experience = (float) remainder / (float) experienceNeeded;
       experience = round(experience, 2);

       //Set Everything
       player.setLevel(level);
       player.setExp(experience);
     //Level 31 and greater
     } else {
       //Calculate Everything
       double a = 4.5; double b = -162.5; int c = -xp + 2220;
       double dLevel = (-b + Math.sqrt(Math.pow(b, 2) - (4 * a * c))) / (2 * a);
       int level = (int) Math.floor(dLevel);
       int xpForLevel = (int) (4.5 * Math.pow(level, 2) - (162.5 * level) + 2220);
       int remainder = xp - xpForLevel;
       int experienceNeeded = (9 * level) - 158;
       float experience = (float) remainder / (float) experienceNeeded;
       experience = round(experience, 2);

       //Set Everything
       player.setLevel(level);
       player.setExp(experience);
     }
   }

  private float round(float d, int decimalPlace) {
  BigDecimal bd = new BigDecimal(Float.toString(d));
  bd = bd.setScale(decimalPlace, BigDecimal.ROUND_HALF_DOWN);
  return bd.floatValue();
  }
}