src/main/java/org/vanilladb/bench/util/RandomPermutationGenerator.java
public void next() {
		for (int k = a.length - 1; k > 0; k--) {
			int w = (int) Math.floor(Math.random() * (k + 1));
			int temp = a[w];
			a[w] = a[k];
			a[k] = temp;
		}

	}
public void next() {
		for (int k = a.length - 1; k > 0; k--) {
			int w = (int) Math.floor(Math.random() * (k + 1));
			int temp = a[w];
			a[w] = a[k];
			a[k] = temp;
		}

	}
It produces the next random permutation