University of Maryland Computer Science researcher Bill Pugh suggested this way while implementing singleton in Java,

SingletonBillPughExample.java

public class SingletonBillPughExample {
    
	private SingletonBillPughExample() {
	    // private constructor
	}

	private static class SingletonHolder {
		private static final SingletonBillPughExample INSTANCE = new SingletonBillPughExample();
	}

	public static SingletonHolder getInstance() {
		return SingletonHolder.INSTANCE;
	}
}