Errors in Master Exam?!

[Marcus Moreno]

Hi,

I think I found 2 errors in the Master Exams of the K&B SCJP 6.0 book -
1. the explanation says that legal identifiers could only start with
letters, "_" and the dollar sign. This is not true -
it may be any kind of money sign - the book imho is correct here.
In other words, you may also use the euro, pound, yen ... signs as the first letter of a legal java identifier.

2. "Is a Relationships always require 2 class types".
What about an interface? An interface is not a class, I would say,
yet e.g. "A String is an Object" I would say.

Cheers,

Marcus

[Paul Campbell]

Originally posted by Marcus Moreno:
Hi,

2. "Is a Relationships always require 2 class types".
What about an interface? An interface is not a class, I would say,
yet e.g. "A String is an Object" I would say.

Cheers,

Marcus

interface TestInterface { }
 
class Parent implements TestInterface {
}
 
class Child extends Parent { }
 
class Animal implements TestInterface {}
class Dog extends Animal {}
 
public class WhatAmI {
public static void main(String[] args) {
Parent p1 = new Parent();
Child  c1 = new Child();
Animal a1 = new Animal();
Dog    d1 = new Dog();
TestInterface[] isA = new TestInterface[4];

isA[0] = p1; //Parent is a TestInterface
isA[1] = c1;// Child is a TestInterface
isA[2] = a1;//Animal is a TestInterface
isA[3] = d1;//Dog is a TestInterface;

for (TestInterface x:isA) {
System.out.println("Is " + x.getClass() +" a TestInterface? " + (x instanceof TestInterface));
}
}
}

Is class Parent a TestInterface? true
Is class Child a TestInterface? true
Is class Animal a TestInterface? true
Is class Dog a TestInterface? true