Java SCJP on Android

About Java SCJP on Android Android App

333 Questions to help study for the SCJP Sun Certified Programmer for Java 6 Exam.

Asks a series of multiple choice questions to help study for the SCJP Version 1.6 exam.

The questions are displayed in random batches of 10 and a score is given at the end.

If a question is answered incorrectly, the correct answer is displayed and explained. Exam tips are displayed for some of the harder questions.

An example question is

What will be the result of attempting to compile and run the following code?

abstract class Base {
abstract void amethod();
static int i;
}
public class DLSoftwareSolutions extends Base{
public static void main(String argv[]){
int[] dl=new int[10];
for(i=0;i < dl.length;i++)
System.out.println(dl[i]);
}
}
OPTIONS

1) a sequence of 10 0's will be printed
2) Error: dl is used before it is initialized
3) Error: DLSoftwareSolutions must be declared abstract
4) IndexOutOfBoundes Error

ANSWER 3

The answer is 3) DLSoftwareSolutions must be declared abstract.

A class that contains an abstract method must itself be declared as abstract.

Exam Tip
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abstract methods must be implemented by a subclass, so they must be inheritable.
abstract methods cannot be private.
abstract methods cannot be final.
abstract methods may have parameters, a return type, and optional throws clause, but are not implemented.
abstract methods end in a semicolon-no curly braces.
A single abstract method in a class means the whole class must be abstract.
An abstract class can have both abstract and nonabstract methods.