A simple way to create smooth random numbers in java

NumberUtil.java

import java.util.Random;

public class NumberUtil {

	public static int getRandomNumberRange(int min, int max) {
		Random random = new Random();
		return random.nextInt(max - min) + min;
	}
}

SmoothRandom.java

import java.util.ArrayList;
import java.util.List;

public class SmoothRandom {

	private int low;
	private int high;

	public SmoothRandom(int low, int high) {
		this.low = low;
		this.high = high;
	}
	
	public List<Integer> generate(int maxamount, int change) {
		List<Integer> out = new ArrayList<Integer>();
		int val = (high/2)+low;
		for (int x=0; x<maxamount; x++) {
			int rand = NumberUtil.getRandomNumberRange(val-change, val+change);
			while (rand > high || rand < low) {
				rand = NumberUtil.getRandomNumberRange(val-change, val+change);
			}
			out.add(rand+val);
		}
		return out;
	}
	
	public List<List<Integer>> generate3d(int maxX, int maxY, int change) {
		List<List<Integer>> out = new ArrayList<List<Integer>>();
		List<Integer> line1 = generate(maxX, change);
		out.add(line1);
		for (int y=0; y<maxY; y++) {
			List<Integer> line = new ArrayList<Integer>();
			out.get(out.size()-1).forEach(number -> {
				int rand = NumberUtil.getRandomNumberRange(number-change, number+change);
				while (rand > high || rand < low) {
					rand = NumberUtil.getRandomNumberRange(number-change, number+change);
				}
				line.add(rand);
			});
			out.add(line);
		}
		return out;
	}
}