Add java8-features module: runnable demos and captured output for the ankurm.com java8-features article

java8-features/broken/CaptureError.java

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+import java.util.function.Supplier;
+
+/** Fails to compile on purpose: a lambda may only capture effectively final locals. */
+public class CaptureError {
+    public static void main(String[] args) {
+        int counter = 0;
+        Supplier<Integer> s = () -> counter;
+        counter++;
+        System.out.println(s.get());
+    }
+}

java8-features/broken/DiamondError.java

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+/** Fails to compile on purpose: two default methods with the same signature and no override. */
+public class DiamondError {
+    interface A { default String move() { return "a"; } }
+    interface B { default String move() { return "b"; } }
+    static class C implements A, B { }
+    public static void main(String[] args) { System.out.println(new C().move()); }
+}