// lowlevel/CircularSet.java

// (c)2017 MindView LLC: see Copyright.txt

// We make no guarantees that this code is fit for any purpose.

// Visit http://OnJava8.com for more book information.

// Reuses storage so we don't run out of memory

import java.util.*;

public class CircularSet {

private int[] array;

private int size;

private int index = 0;

public CircularSet(int size) {

this.size = size;

array = new int[size];

// Initialize to a value not produced

// by SerialNumbers:

Arrays.fill(array, -1);

}

public synchronized void add(int i) {

array[index] = i;

// Wrap index and write over old elements:

index = ++index % size;

}

public synchronized boolean contains(int val) {

for(int i = 0; i < size; i++)

if(array[i] == val) return true;

return false;

}

}