The Power of Java Enum - Factory Design Pattern

Java Enums are a powerful tool, let’s use them to create an instance of a class with factory design pattern.

public enum Document {
	TEXT {
		@Override
		public IDocument getNewInstance() {
			return new TextDocument();
		}
	},
	WORD {
		@Override
		public IDocument getNewInstance() {
			return new WordDocument();
		}
	};

	/**
	 * @return IDocument new instance of specific IDocument
	 */
	public abstract IDocument getNewInstance();
};

public interface IDocument {
	String getTitle();
}

Create a list of document instances:

private static List<IDocument> createDocuments(List<Document> docTypes){
	return docTypes.stream()
			.map(Document::getNewInstance)
			.collect(Collectors.toList());
}

Pros:

• Loose coupling, depend on abstractions, not concrete implementations;
• Control the types of instances that are created;
• Lazy instantiation, use the enum value until you need the concrete object to be created.
• Clean and concise code.

Cons:

• The instantiation method is a generic one and will depend on the same parameters, regardless of the specific object that needs to be created.