Java testing

ConstructorReference.java

import java.util.function.IntFunction;

public class ConstructorReference {
	public static void main(String...args) {
		IntFunction<Integer> intMakerSingle = Integer::new;
		int intSingle = intMakerSingle.apply(40);  // int value

		IntFunction<int[]> intMakerArray = int[]::new;
		int[] intArray = intMakerArray.apply(100);  // array size
	}
}

OuterClass.java

public class OuterClass {
	int x = 1;
	Sub sub;

	public OuterClass() {
		sub = this.new Sub();
	}

	class Sub {
		int x = 2;

		void f() {
			System.out.println("sub f" + OuterClass.this.sub.x);
		}
	}

	public static void main(String...args) {
		OuterClass outerClass = new OuterClass();
		Sub sub = outerClass.new Sub();
		sub.f();
	}
}

TestFunctionalInterface.java

interface MyFunctionalInterface {
	void call();
}

// not implementing MyFunctionalInterface
class SampleClass {
	static void printer() {
		System.out.println("Printer");
	}
}

public class TestFunctionalInterface {
	public static void main(String...args) {
		user(SampleClass::printer);  // still callable on matching interface
	}

	static void user(MyFunctionalInterface f) {
		f.call();
	}
}