007 - Classes and Objects Flashcards
In a class declaration. The __________ (the area between the braces) contains all the code that provides for the life cycle of the objects created from the class:
class body
The class body contains: A. \_\_\_\_\_\_\_\_\_\_ for initializing new objects B. \_\_\_\_\_\_\_\_\_\_ for the fields that provide the state of the class and its objects C. \_\_\_\_\_\_\_\_\_\_ to implement the behavior of the class and its objects.
constructors
declarations
methods
class declarations can include these components, in order:
- _________ such as public, private.
- _________, with the initial letter capitalized.
- __________ preceded by the keyword extends.
- _________ preceded by the keyword implements.
- __________, surrounded by braces, {}.
- Modifiers
- The class name
- the class’s parent (superclass), if any. (A class can only extend (subclass) one parent.)
- A comma-separated list of interfaces implemented by the class, if any (A class can implement more than one interface.)
- The class body
There are several kinds of variables:
- Member variables in a class: __________.
- Variables in a method or block of code: __________.
- Variables in method declarations: __________.
fields
local variables
parameters
Field declarations are composed of three components, in order:
- __________, such as public or private.
- The field’s __________.
- The field’s __________.
- Zero or more modifiers
- type
- name
__________ used lets you control what other classes have access to a member field.
The first (left-most) modifier
__________—the field is accessible from all classes.
public modifier
__________ —the field is accessible only within its own class.
private modifier
In the spirit of encapsulation, it is common to make fields __________.
private
All variables must have a __________.
You can use __________ such as int, float, boolean, etc.
Or you can use __________, such as strings, arrays, or objects.
type
primitive types
reference types
the same naming rules and conventions are used for method and class names, except that
the first letter of a class name \_\_\_\_\_\_\_\_\_\_, the first (or only) word in a method name \_\_\_\_\_\_\_\_\_\_.
should be capitalized
should be a verb
The only required elements of a method declaration are: the method's \_\_\_\_\_\_\_\_\_\_, the method's \_\_\_\_\_\_\_\_\_\_, a pair of \_\_\_\_\_\_\_\_\_\_, and a \_\_\_\_\_\_\_\_\_\_.
return type
name
parentheses, ()
body between braces, {}
More generally, method declarations have six components, in order:
1__________such as public, private.
- __________ the data type of the value returned by the method, or void.
- __________ the rules for fields apply to methods as well, convention is a little different.
- __________ in parenthesis.
- __________ to be discussed later.
- __________, enclosed between braces.
- Modifiers
- The return type
- The method name
- The parameter list: a comma-delimited list of input parameters, preceded by their data types, enclosed by parentheses, (). If there are no parameters, you must use empty parentheses.
- An exception list
- The method body: the method’s code, including the declaration of local variables, goes here.
Two of the components of a method declaration comprise the method signature: __________ and __________.
the method’s name
the parameter types
Definition: Two of the components of a method declaration comprise __________: the method’s name and the parameter types.
the method signature
By convention, method names should be __________ or __________, followed by adjectives, nouns, etc.
In multi-word names, the first letter of each of the second and following words __________.
a verb in lowercase or a
multi-word name that begins with a verb in lowercase
should be capitalized
Typically, a method has a unique name within its class. However, a method might have the same name as other methods due to __________.
method overloading
Java can distinguish between methods with different __________.
method signatures
__________ means that methods within a class can have the same name if they have different parameter lists
Method overloading
Overloaded methods are differentiated by the __________ and the __________ of the __________ passed into the method.
The number and the type of the arguments
You cannot declare more than one method with the same name and the same number and type of arguments, because __________.
the compiler cannot tell them apart
__________, so you cannot declare two methods with the same signature even if they have a different return type.
The compiler does not consider return type when differentiating methods
__________ should be used sparingly, as they can make code much less readable.
Overloaded methods
Constructor declarations look like method declarations—except that __________ and __________.
they use the name of the class and have no return type
To create a new Bicycle object called myBike, __________ is called by __________
a constructor
the new operator
Bicycle myBike = new Bicycle(30, 0, 8);
new Bicycle(30, 0, 8)
creates __________ for the object and initializes __________.
space in memory
its fields
As with methods, the Java platform differentiates __________ on the basis of the number of arguments in the list and their types.
constructors
You cannot write two constructors that have the same number and type of arguments for the same class, because the platform would not be able to tell them apart. Doing so causes a __________.
compile-time error
You don’t have to provide any constructors for your class, but you must be careful when doing this. The compiler automatically __________ for any class without constructors.
provides a no-argument, default constructor
If your class has no explicit superclass, then it has an __________, which does have a no-argument constructor.
implicit superclass of Object
You can use __________in a constructor’s declaration to control which other classes can call the constructor.
access modifiers
__________ refers to the ilist of variables in a method declaration. __________ are the actual values that are passed in when the method is _________.
Parameters
Arguments
invoked
You can use a construct called __________ to pass an arbitrary number of values to a method. You use it when you don’t know how many of a particular type of argument will be passed to the method.
varargs
__________ is a shortcut to creating an array manually.
varargs
To use varargs, you follow the type of the last parameter by __________ then a space, and __________. The method can then be called with any number of that parameter, including __________.
an ellipsis (three dots, …),
the parameter name
none
You will most commonly see varargs with __________.
the printing methods;
for example, this printf method:
public PrintStream printf(String format, Object… args)
allows you to print an arbitrary number of objects. It can be called like this:
System.out.printf(“%s: %d, %s%n”, name, idnum, address);
or like this
System.out.printf(“%s: %d, %s, %s, %s%n”, name, idnum, address, phone, email);
The __________ of a parameter must be unique in its scope. It cannot be __________ for the same method or constructor, and it cannot be __________ of a local variable within the method or constructor.
name
the same as the name of another parameter
the name
A parameter can have the same name as one of the class’s fields. If this is the case, the parameter is said to __________ the field.
shadow
__________ can make your code difficult to read and is conventionally used only within constructors and methods that set a particular field.
Shadowing fields
Primitive arguments, such as an int or a double, are passed into methods __________. This means that any changes to the values of the parameters exist only within the scope of the method. When the method returns, the parameters __________ and any changes to them __________.
by value
are gone
are lost
Reference data type parameters, such as objects, are also passed into methods __________. This means that when the method returns, the passed-in reference __________ However, the values of the object’s fields __________ in the method, if they have __________.
by value
still references the same object as before.
can be changed in the method, if they have the proper access level.
An object creation statement can have three parts:
- __________: associate a variable name with an object type.
- __________: The new keyword is a Java operator that creates the object.
- _________: The new operator is followed by a call to a constructor, which initializes the new object.
- Declaration
- Instantiation
- Initialization
Simply declaring a reference variable __________ For that, you need to use the __________.
does not create an object.
new operator
The new operator __________ by allocating memory for a new object and returning a reference to that memory. The new operator also invokes __________.
instantiates a class
the object constructor
The phrase “instantiating a class” means the same thing as “_________”
creating an object.
The new operator requires a single, postfix argument: a call to a _________.
constructor
