Anonymous Inner Class

[Thomas Hauck]

line 1: The parent class Mammal is defined.
line 2: The abstract class Human is defined.
line 3: The anonymous inner class begins on line 3.
line 4: Contains the implementation of the abstract method.
line 5: The reference created on line 3 is used to call the method that has been implemented.

class Mammal {                        // line 1
	public Mammal(int i) {
	}
}

abstract class Human extends Mammal { // line 2
	public Human(int i) {
		super(i);
	}
	public abstract void move();
}

class TestClass {
	public static void main(String[] args) {
		Human h1 = new Human(3) {      // line 3
			public void move() {       // line 4
				System.out.println("In Human.move()");
			}
		};
		h1.move();	                //line 5
	}
}

Question 1: Does the anonymous inner class begin on line 3?

Question 2:
Is a characteristic of the anonymous inner class the following :
A reference created outside of the class is used to invoke a method of the inner class?

[Roel De Nijs]

Are inner classes not on the OCPJP7 exam instead of OCAJP7

Thomas Hauck wrote:Does the anonymous inner class begin on line 3?

Yes.

Thomas Hauck wrote:Is a characteristic of the anonymous inner class the following :
A reference created outside of the class is used to invoke a method of the inner class?

If you have a reference variable which refers to an anonymous inner class object, you can only invoke the methods which are defined by the type of the reference variable.

A few examples to illustrate:

If you change the type of variable h1 to Mammal line 5 will give a compiler error (The method move() is undefined for the type Mammal

If you would add a public method eat() to the anonymous inner class (e.g. between line 3 and 4 or before the line with };), it will be impossible to invoke this method using the reference variable h1 (because it's not defined in Human, the type of the variable). It is however possible to invoke the eat() method from within the move() method.

I don't know if this answers your question...

[Thomas Hauck]

Hi Roel,

Inner classes are tested in exam 1Z0-804,
but some candidates have said that they have seen questions with respect to inner classes on 1Z0-803.

I just want a high level understanding of this topic in case a question is asked.

I have made your suggested changes below.

class Mammal {                        // line 1
	public Mammal(int i) {
	}
}

abstract class Human extends Mammal { // line 2
	public Human(int i) {
		super(i);
	}
	public abstract void move();
}

class TestClass {
	public static void main(String[] args) {
		Human h1 = new Human(3) {      // line 3
			public void move() {       // line 4
				System.out.println("In Human.move()");
				eat();
			}
			public void eat(){
				System.out.println("Humans need to eat because they are subclasses of Mammal.");
			}
		};
		h1.move();	                //line 5
	}
}
/* Program output 
In Human.move()
Humans need to eat because they are subclasses of Mammal
*/

[Roel De Nijs]

Thomas Hauck wrote:Inner classes are tested in exam 1Z0-804,
but some candidates have said that they have seen questions with respect to inner classes on 1Z0-803.

Can you give some reference of this statement? According to this blog article (from Oracle Education): There should not be any questions on the exam that are not addressed in the exam topics.

[Thomas Hauck]

This link
https://blogs.oracle.com/certification/entry/0620a contains

several videos.

For the links at the bottom

1. Certification Track: Oracle Certified Associate (OCA) - Java SE 7 Programmer
2. Certification Track: Oracle Certified Professional (OCP) - Java SE 7 Programmer
3. Certification Exam: Java SE 7 Programmer I (1Z0-803)
4. Certification Exam: Java SE 7 Programmer II (1Z0-804)
5. Certification Exam: Upgrade to Java SE 7 Programmer (1Z0-805)
6. Register Now: Pearson VUE


When I click on the 3rd link down I go to

http://education.oracle.com/pls/web_prod-plq-dad/db_pages.getpage?page_id=5001&get_params=p_exam_id:1Z0-803&p_org_id=&lang=

which is a registration page.
----
I have read in the book from Mala Gupta

OCA Java SE 7

that "Inner Classes" are not covered on the exam.
I have also read that "try-with-resources" are not covered on the (1Z0-803).

Different testing companies (Whizlabs and Enthuware)
pose different questions independent of the testing outline from Oracle.

For example:
1) Whizlabs Test Questions have questions on
a) try-with-resources b) Catching Multiple Exception Types
http://docs.oracle.com/javase/7/docs/technotes/guides/language/catch-multiple.html

2) Enthuware Test Questions have questions on
a) Inner Classes

Enthuware authors have said in their test explanations that testers have received questions with regards to "Inner Classes".

Both of the examples listed above may be outside the scope of the testing outline for 1Z0-803.
I understand for the "OCA forum" it is beneficial for the participants if the subject matter is streamlined based on the test outline from Oracle.

Should questions on
1) try-with-resources
2) Catching Multiple Exception Types
3) Inner Classes

be posted to the forum OCP JP7 1Z0-804 forum?

That would be a good recommendation so that the OCA forum does not become
diluted with "test topics" that may not appear on the actual exam.

[Roel De Nijs]

Thomas Hauck wrote:Should questions on
1) try-with-resources
2) Catching Multiple Exception Types
3) Inner Classes

be posted to the forum OCP JP7 1Z0-804 forum?

None of these topics appear in the exam topics list of OCAJP7, but they do appear on the exam topics list of the OCPJP7 (inner classes mentioned as nested classes). It seems reasonable to post questions on these topics only in the OCPJP forum.

(that's why I moved this topic to the OCPJP forum)