QUESTIONS AND ANSWERS
/Is it possible to create an array in Java where the first row has 5 elements, the second
row has 6 elements and the third row has 2 elements? - Answer-yes
/.create a for loop to execute: Is it possible to create an array in Java where the first row
has 5 elements, the second row has 6 elements and the third row has 2 elements? -
Answer-double [] [] salaries = new double [NUM_STORES][];
array[0] = new double [5];
array[1] = new double [6];
array[2] = new double [2];
/.Write the statement to print the number of elements in a one-dimensional array. -
Answer-for(i =0; i<array.length -1; i++)
{
System.out.println(array[i]);
}
/.What does Java initialize the elements of an array of references to? - Answer-null
/.What does Java initialize an array of ints to? - Answer-0
/.Is an array an object? - Answer-Yes
/.int [ ] numbers = new int[16] how many objects were created? - Answer-1, new was
used once
/.Student [ ] roster = new Student[25] <- how many objects were created? - Answer-1,
new was used once
/.Write the command to compile a source code file named Book.java - Answer-javac
Book.java
/.Write the command to run a class file named Book.class - Answer-java Book
/.Where does the execution of a Java project begin? - Answer-public static void
main(String [] args)
/.How many public classes can a Java class file contain? - Answer-1
/.Can you declare fields of a class inside a method? - Answer-No
, /.What does private access for a field mean? - Answer-Only the current class will have
access to the field or method.
/.What does public access for a field mean? - Answer-Any class can refer to the field or
call the method.
/.What does protected access for a field mean? - Answer-Only the current class and sub
classes (and sometimes also same-package classes) of this class will have access to
the field or method.
/.What happens if you do not specify the access for a field? - Answer-It will set the
access to package
/.Can a sub-class also be a super-class? - Answer-Yes, Java allows this
/.What is an abstract method? - Answer-It is a method that is declared, but contains no
implementation
/.What is an abstract class? - Answer-Is a class that is declared abstract —it may or
may not include abstract methods. Abstract classes cannot be instantiated, but they can
be sub classed.
/.Does a super class have to be abstract? - Answer-No
/.How many classes can a class directly inherit from? - Answer-1
/.How many interfaces can a class implement? - Answer-Multiple or unlimited
/.What can a Java interface contain? - Answer-Consists of modifiers, the keyword
interface, the interface name, a comma-separated list of parent interfaces (if any), and
the interface body
/.Can an interface be instantiated? - Answer-You can never instantiate an interface in
java.
/.Does the is-a relationship apply to classes that implement an interface? - Answer-No
/.What is the difference between overloading a method and overriding a method? -
Answer-Overloading: is the ability to create multiple methods of the same name with
different implementations.
Overriding: is a language feature that allows a subclass or child class to provide a
specific implementation of a method that is already provided by one of its superclasses
or parent classes.
/.What class does every class indirectly inherit from? - Answer-Object class