package essentials;

/*
 * Examples showing how to declare and instantiate an anonymous class. An
 * anonymous class declaration is an expression that defines the members of a
 * class and creates an instance of that class at the same time. They are
 * relevant for code that only needs to use a class once. Some anonymous class
 * declarations can also be written more succinctly as lambda expressions.
 */
public class AnonymousClasses
{
	private static final int MIN_LENGTH = 5;
	
	private static final StringSelector SELECT_ALL = new StringSelector()
			{		
				@Override
				public boolean accept(String string)
				{
					return true;
				}
			};
	
	public static void main(String[] args)
	{
		// Simple anonymous class implementing an interface
		StringSelector selectUpperCase = new StringSelector() 
				{
					@Override
					public boolean accept(String string)
					{
						return string.equals(string.toUpperCase());
					}
				};
		System.out.println(selectUpperCase.getClass());
		System.out.println(selectUpperCase.accept("UPPER"));
		
		// Anonymous class with variable capture
		int maxLength = 5;
		StringSelector selectSizeAndNotEquals = new StringSelector() 
				{
					@Override
					public boolean accept(String string)
					{
						return !string.equals(args[0]) && 
								string.length() <= maxLength && 
								string.length() >= MIN_LENGTH;
					}
				};
		if (args.length > 0 && args[0] != null )
		{
			System.out.println(selectSizeAndNotEquals.accept("A string"));
		}
		
		// Anonymous class through inheritance and with field and methods
		Object object = new Object() {
			
			private int numberOfCalls = 0;
			
			private String getMessage()
			{
				return String.format("%s (called %d times)", 
						super.toString(), ++numberOfCalls);
			}
			
			@Override
			public String toString() 
			{
				return getMessage();
			}
		};
		System.out.println(object.toString());
		System.out.println(object.toString());
	}
}

interface StringSelector
{
	boolean accept(String string);
}