package singleton.classloading;

/**
 * This example shows that you need to be careful to ensure that
 * singletons are not accessed before they are created!
 */
class S {
	private static S instance;
	public static int numInstances;
	public static S getInstance() {
		if (instance == null) {
			instance = new S();
		}
		return instance;
	}

	private S() {
		S.numInstances++;
		B.doNothing();  // B is loaded here, during A's constructor
	}
}

class B {
	// B caches the only instance of S
	public static S a = S.getInstance();
	public static void doNothing() {}
}

class Main {
	public static void main(String[] args) {
		System.out.println(S.getInstance() == B.a); // false!
		System.out.println(S.numInstances);         // 2!
	}
}