Do interfaces have toString method? [duplicate]

Question

How is it possible to call toString method using the reference variable of interface Test, which does not have a toString method?

interface Test
{
    void show();
    String toHi();
}
class Demo implements Test
{
    public void show(){
        System.out.println("Show");
    }
    public String toString(){
        return "Hello"; 
    }
    public String toHi(){
        return "Hi";    
    }

    public static void main(String[] args) 
    {
        Test t=new Demo();
        String s=t.toString();
        System.out.println(s);
    }
}

Answer 1

Since class Demo implicitly extends class Object, it inherits method toString. And since that's not an abstract method, class Demo is not forced to provide an implementation, although you're able to directly invoke toString on an instance of Demo. For more information, please see Lesson: Interfaces and Inheritance.

As stated in the Object API,

Class Object is the root of the class hierarchy. Every class has Object as a superclass. All objects, including arrays, implement the methods of this class.

Also, note that the toString method is not part of the interface definition, but rather the Object class definition.