Following implementation shows a classic Singleton design pattern:

public class ClassicSingleton {

	private static ClassicSingleton instance = null;

	protected ClassicSingleton() {
		// Exists only to defeat instantiation.
	}

	public static ClassicSingleton getInstance() {
		if(instance == null) {
			instance = new ClassicSingleton();
		}
		return instance;
	}

}