(New) CS 1331 Final Exam Review Terms

type

A class is a "____"

Data and methods

What are the two main attributes of a class?

Instance data

Values that are within the class but not within the methods; generally placed at the top of the class

copy

Each object that gets instantiated for the class gets its own ____ of the instance variables

Methods

functions/procedures (behaviors) within the class

body

public double meth1(int var1, int var2) {
  double total;
  total = var1 * var2;
  return total;
}

//What is the content of the method referred to as?

Return statement

control immediately goes back to call

return;

What is the return statement for a void method?

Local variables

Variables declared inside a method, and are only accessible in that method. In other words, the scope of these variables is the method in which they were created.

Parameters

Variables passed into a method

Formal paramaters

Names of the parameters in the header declaration

Actual paramaters

Values passed in when running

T

(T/F) Arrays can be parameters

Static methods

Methods that are not called in the context of an object.

Non-static methods

Methods that are always called in the context of an object

this

A Java reserved word that is used inside methods. It refers to the object upon which the method was invoked.

Class interface

A group of specified certain methods for outsiders to use

Visibility modifiers

Modifiers that control access

public

Modifier that allows anyone to access instance data and methods

private

Modifier that only allows the class itself to access instance data and methods (i.e. objects of that class)

protected

Modifier that allows a subclass to access instance data and methods from its super class, vice versa, and classes within the same package

Constructor

A special method that is automatically called when objects are instantiated.

initialize

A constructor's primary use is to _______ instance variables.

Scope

The region of a program where variables are accessible.

Overloading

The use of the same name with different paramater lists (types) to create multiple versions of a method

Method signature

The part of a method declaration that includes the name, along with the paramater type and order.

Example:

meth1(int var1, int var2)

F

(T/F) A method signature includes the return type of that method

T

(T/F) Constructors can be overloaded

this(v1, v2, v3);

What is the proper syntax for a chained constructor call? (use 3 variables, denoting them as v1, v2, v3)

F

(T/F) A constructor must always have parameters as input

B

If a constructor for a class is not written, Java provides one for you when you create an object of that class. However, if you provide one with pamaraters, and you create an object with no paramaters, what happens?

A. The object is created with default values, and the code compiles.
B. The compiler will throw an exception.

A

int a; 

What is this an example of?

A. Declaration

B. Initialization

C. Instantiation

A

String s;  

What is this an example of?

A. Declaration

B. Initialization

C. Instantiation

B

int a;

 a = 0; //What does this line represent?

A. Declaration

B. Initialization

C. Instantiation

C

String s;

s = new String(“Hello”); //What does this line represent?

A. Declaration

B. Initialization

C. Instantiation

equals()

If we want to check whether two objects contain the same values, what method or operator do we use (hint: primarily used for objects)?

==

If we want to check whether two objects reference the same data, what method or operator do we use (hint: primarily used for primitive types)?

toString()

The method invoked when an attempt to print an object of that type occurs

static

A modifier that creates one copy of a variable or method that is shared by all instances of the class

In the class

Where is the memory space for static variables located?

F

(T/F) Static methods can reference instance variables

null

A reserved word for objects that have no reference; can occur after declaration but no instantiation

Copy constructor

A special type of constructor that takes in an object of that class and "copies" its contents. When called, an object with the same values as the paramater object will be created.

Wrapper classes

A class that corresponds to a primitive type. Allows the usage of primitive types as objects. i.e. Integer, Double, etc.

T

(T/F) Java will automatically convert between primitive and Wrapper when needed

Auto-boxing

Converting a wrapper to a primitive type

Unboxing

Converting a primitive type to a Wrapper

Javadoc

Documenting your code

Inheritance

The process of deriving a new class from an existing one. Automatically contains some or all of the methods of the original. Can add new ones to it.

extends

A keyword that denotes that a class is a subclass of a super class; placed in class header

is-a

What type of hierarchy represents the super-sub class relationship?

super

keyword for denoting access to parent's members

super(v1);

What is the proper syntax for calling the constructor of the parent class from the child class? Use "v1" as the variable.

F

(T/F) When using the super() call in the constructor of the child class, this line of code can appear anyhwere within the body of the constructor.

T

(T/F) If the first line of a sub-class constructor is not an explicit call to a super class constructor, Java inserts super() automatically.

Overriding

When a child class defines a method with the same name (and signature) as the parent, child's version overrides the parent's version

@Override

What is the correct syntax for notifying the compiler of a method override for a child class?

F

(T/F) Static methods can be inherited and overridden

single

Java has _____ inheritance; it can extend at most one class

Object

The class that all classes are ultimately derived from. Contains methods such as equals(), toString(), clone().

instanceof

keyword that checks if an object is an instance of another class

getClass()

Method that returns the class an object is an instance of

this(xxxx);

chained constructor call (use xxxx as param, variable, or method name)

this.xxxx;

Instance data of object that is being called upon.
(use xxxx as param, variable, or method name)

this.xxxx();

Calling a method within the class, do not necessarily need "this"
(use xxxx as param, variable, or method name)

super(xxxx);

calling super class constructor
(use xxxx as param, variable, or method name)

super.xxxx;

Accessing instance variable from super class. (use xxxx as param, variable, or method name)

Abstract

a “placeholder;” useful for super and sub classes in which the super class contains a abstract method that must be included in the subclasses.

F

(T/F) Abstract classes cannot contain non-abstract methods

T

(T/F) In order for an abstract method to exist, the subclasses must either override the method or be absract themselves.

can

Abstract methods (can/can’t) have concrete constructors.

F

(T/F) You can instantiate an abstract class with new()

final

A keyword that is used to denote that a class cannot be extended, the value of a variable cannot be changed, or that a method cannot be overridden.

Static type

A variable’s type at compile time; what class the object is declared as

Person

Suppose a Person class with a constructor and methods is created. Also suppose that a subclass named Student is created and extends Person. Now, suppose we create a Person object p and write the following lines of code.

Person p;

p = new Student(“Mary”, 1);

//What is the static type of p?

Dynamic type

the type of object a variable references at run-time; the class an object is instantiated as.

Dentist

Suppose a Person class with a constructor and methods is created. Also suppose that a subclass named Dentist is created and extends Person. Now, suppose we create a Person object p and write the following lines of code (assume “xxxx” are paramaters).

Person p;

p = new Dentist(xxxx);

//What is the dynamic type of p?

F

(T/F): If you do not write a toString() method for a class and attempt to print an object that is an instance of that class, you will get a compiler error.

public abstract void method1()

Write the method declaration of an abstract void method that takes no parameters, is public, and is named “method1”.

Polymorphism

To have many forms. This allows us to deal with diverse (but related) members of a group in a general way.

yes

Suppose a class Animal is defined, and Bird is another defined class that is a subclass of Animal. Are the following lines of code legal? (yes/no)

Animal a1;

a1 = new Bird();

no

Suppose a class Animal is defined, and Bird is another defined class that is a subclass of Animal. Are the following lines of code legal? (yes/no)

Animal a1;

Bird b1 = new Animal();

T

(T/F) We can assign or subsittute a member of a subclass for a memer of a parent class, but not vice versa

Dynamic binding

Binding of which type of object is “in there” and influences the call is is deferred until run-time; Compiler simply insures either way is legal.

dynamic

Suppose obj is an instantiated object of some subclass, and meth() is a method that exists in both the parent and super class. The method that was invoked on a obj.meth() call is determined by the ____ run-time type of obj.

lowest

In a chain of multiple subclasses, whatver class is ____ in hierarchy determines which methods are called.

F

(T/F) You cannot cast an object down the hierarchy (casting parent to a child)

T

(T/F) It is possible for valid casts to fail at run-time.

Generics

Classes and method definitions with types. You write a _____ class/method, then it can be created to handle any different type of object.

ArrayList

Like an array, like a list (can grow in size).

import java.util.ArrayList;

Write the line of code that imports an ArrayList for use.

ArrayList<Type> list = new ArrayList<>();

How do you correctly declare and instantiate an ArrayList? Use “Type” and “list” in your answer when appropriate.

to the right

When you add an object to an ArrayList at a particular index, which way does the rest of the list shift?

Interfaces

Specification of a set of abstract behaviors (methods). Classes choose to provide these behaviors and then advertise themselves as doing so.

F

(T/F) A class does not have to implement every method in the interface it implements.

T

(T/F) A class can have other methods besides the ones it implements from an interface.

F

(T/F) An interface is a class.

T

(T/F) Interfaces can be in hierarchies

Recursion

One made to same method as resident in; The process of calling a method within the method itself.

F

(T/F) Recursive calls are essentially “calling yourself”