Created attachment 161530 [details]
Error

Product Version: NetBeans IDE Dev (Build 201606280002)
Java: 1.8.0_60; Java HotSpot(TM) 64-Bit Server VM 25.60-b23
Runtime: Java(TM) SE Runtime Environment 1.8.0_60-b27
System: Windows 10 version 10.0 running on amd64; Cp1250; pl_PL (nb)

1. Create a class which extends java.util.Date:

public class NewClass1 extends Date {

    private static final long serialVersionUID = 1L;

}

2. On the class name you will have a hint to implement clone() - do it:

public class NewClass1 extends Date {

    private static final long serialVersionUID = 1L;

    @Override
    public Object clone() {
        return super.clone();
    }

}

3. On the clone() method you will see a hint to declare CloneNotSupportedException - do it:

public class NewClass1 extends Date {

    private static final long serialVersionUID = 1L;

    @Override
    public Object clone() throws CloneNotSupportedException {
        return super.clone();
    }

}

4. You end up with an error, because the overridden method does not throw CloneNotSupportedException.