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May 2000



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Answers' appropriateness

Posted by Mekala on May 09, 2000 at 9:38 AM

> While trying to learn Java, I'm making flashcards until I get
> the basics down. I'd be grateful if you could review the Q/A's
> below and send any corrections to:
> I'd also appreciate any new Q/A's for my flashcards or
> elaborations on Q/A's below. Thanks, Steve

> Q1 Explain the appearance of a constructor, when compared to a
> method.

> A1 A constructor looks like a method, but it lacks a return
> type.

In addition to that Constructor should have the same name as the class name.

> Q2 Identify constructors and initializers in class CoffeeCup:
> class CoffeeCup {
> private int innerCoffee;
> //..
> }
> A2 There are none.

You are absolutely correct. JVM will create one default constructor for you. JVM will also initialize the variables which are not inside methods.

> Q3 Declare an uninitialized array of Point named myPoints.

> A3 Point myPoints[];

> Q4 In the code below, allocate an array of ten references to
> Point, called myPoints, that are initialized to the null
> reference:
> Point myPoints[];
> A4 myPoints = new Point[10]; (note: invalid??)

> Q5 Which string object is for read-only objects ?

> A5 The String class is for read-only objects.

> Q6 Which string object is for modifiable objects ?

> A6 The StringBuffer class is for objects that can be modified.

> Q7 String objects provide ? to obtain the number of characters
> in a string.

> A7 String objects provide the length() accessor method to obtain the number of characters in a string.

> Q8 A class definition has some or all of which six items ?

> A8 class variables, instance variables, class methods,
> instance methods, constructors, and static initializers

> Q9 What is a class ?

> A9 A class is a master copy of an object that determines what
> behavior and attributes the object should have.

> Q10 What's the format of a class called Dog ?

> A10 [keywords] class Dog [extends Superclass] [implements Interface] {
> // class body
> }

> Q11 What's a class variable ?

> A11 A class variable is associated with a class of objects,
> not just a single object.

> Q12 What is AWT ?

> A12 AWT stands for Abstract Windowing Toolkit; a set of Java
> classes that has been extended by the Swing windowing classes. They can be used to display and control a GUI.

> Q13 What is an argument ?

> A13 An argument is extra info that is either sent to a program
> at runtime (via the command prompt), or sent to a method during a program.

> Q14 What is an array ?

> A14 An array is a group of variables that share the same name
> and store the same kind of info.

> Q15 public Virus(String name, int size) {
> author = name;
> maxFileSize = size;
> }
> Write an example of code that could be used to call the above
> constructor.

> A15 Virus mumps = new Virus("Hall", 30000);
> or the format....
> Virus [reference] = new Virus("[string]", integer);

> Q15 public Virus(String name, int size) {
> author = name;
> maxFileSize = size;
> }
> The above constructor could be called only if ?

> A15 In the example code, the constructor could be called only
> if a string and an integer were sent as arguments, along
> with the new statement.

> Q16 In OOP, what's an attribute do ?

> A16 An attribute describes an object and distinguishes it from
> others.

> Q17 Where are attributes kept ?

> A17 Attributes are stored in variables.


Your answers are correct


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