Randomchooser

RandomChooser.java

package com.jeuxjeux20.tools.random;

import java.security.InvalidAlgorithmParameterException;
import java.util.HashMap;
import java.util.Map;
import java.util.Random;

/**
 * <p>An {@link HashMap} to get random values followed by its chance to get it. </p>
 * <h5>For example : </h5>
 * <p>We will initialize it with the type {@link String}.</p>
 * <code>RandomChooser&lt;String&gt; myChooser = new RandomChooser<>();</code>
 * <p> We will add two items to it. </p>
 * <code>myChooser.Put("Android",2); <br> myChooser.Put("iOS", 1);</code>
 * <p>For Android, there is a chance of <b>2</b>, and iOS, <b>1</b>. 
 * Which means that there is 2/3 chance for Android to be chosen, and 1/3 chance for iOS to be chosen.</p>
 * <p>Now, let's see what goes out of the box !</p>
 * <code>System.out.println(myChooser.GetRandomItem());<br>> Android</code>
 * <p>Well, looks like Android got there. After all, he had 2/3 chances to be chosen. So not much luck !</p>
 * @author jeuxjeux20
 *
 * @param <T> The used type in the collection
 */
public class RandomChooser<T> extends HashMap<T, Integer>{
	private static final long serialVersionUID = 1L;
	private Random Randomiser = new Random();
	/**
	 * Gives a random item following the chances given by the {@link Integer} values.
	 * @throws InvalidAlgorithmParameterException When there are no items.
	 */
	public T GetRandomItem() throws InvalidAlgorithmParameterException {
		if (this.size() <= 0) throw new InvalidAlgorithmParameterException("No items");
		int sum = 0;
		for(int chance : this.values()) {
			sum += chance;
		}
		int randomValue = Randomiser.nextInt(sum);
		int i = 0;		
		for (Map.Entry<T, Integer> thing : this.entrySet()) {
			if (randomValue < thing.getValue() + i) {
				return thing.getKey();
			}
			else {
				i += thing.getValue();
			}
		}
		throw new InvalidAlgorithmParameterException("idk");
	}
}