Chance.java

import lombok.Getter;

public class Chance {
	
	@Getter
	private Object object;
	@Getter
	private int chance;
	
	public Chance(Object obj, int chance) {
		this.object = obj;
		this.chance = chance;
	}
	
}

ChanceAPI.java

import java.util.List;
import java.util.Random;

public class ChanceAPI {

	private Chance[] chances = null;
	
	public static ChanceAPI init() {
		return new ChanceAPI();
	}
	
	public void add(Chance[] chance) {
		this.chances = chance;
	}
	
	public Object generateRandom() {
		int total = 0;
		for(Chance chance : chances) {
			total += chance.getChance(); 
		}
		
		int rand = new Random().nextInt(total);
		int sum = 0;
		int i = 0;
		while(sum < rand) {
			sum += chances[i++].getChance();
		}
		return chances[Math.max(0, i-1)].getObject();
	}
	
}