How is tag interface functionality implemented in Java continued ...?

//MyTestClass.java

package Pack1;

public class MyTestClass implements Cloneable{

    private int g = 9;

    public void meth(){
        System.out.println(g);
    }

    public Object clone()
    {

        try{
            return super.clone();
        }
        catch ( Exception e ){
            return new String("There was an expection");
        }

    }

}

//Driver.java
package Pack1;

public class Driver {

    /**
     * @param args
     */
    public static void main(String[] args) {
        MyTestClass my = new MyTestClass();

        Object obj = my.clone();

        if (obj instanceof String)
        {
            System.out.println(obj);
        }
        else
        {
            MyTestClass my1 = (MyTestClass)obj;
            my1.meth();
        }

    }

}

This gives "There was an exception" and 9 if I delete and keep the "
implements cloneable interface" in the class declaration

public class MyTestClass implements Cloneable

My question is how does this work ??

If you look at Object.java and Cloneable.java there is not code level
connection !!!

How is the throwing of exception implemented !!!

Thanks,
Ankur