Chapter 4 Java

True or False: Every Java class has at least 1 constructor

True: if you don't define one the compiler gives a no-args constructor that initializes all instance variables to default values (0 for #s, null for objects, false for boolean)

True or False: A class may have more than one constructor.

True; A class may have many different constructors.

True or False: The programmer gives names to objects in his program.

True; A programmer may give his objects any name.

What are accessor methods/accessors/getters?

public methods that return the values of an object's private fields so that an object of a different class can access those values

Several compiled java classes may be collected in one ________

.jar file

What are three benefits of encapsulation?

1. The fields of a class can be made read-only or write-only. 2. A class can have total control over what is stored in its field. 3. The users of a class do not know how the class stores its data. A class can change the data type of a field and users of the class do not need to change any of their code.

What is inheritance?

Can create a new class by extending an existing one.

True or False: A Java program is allowed to create only one object of each class.

False; An infinite number of objects may exist.

True or False: The import statement tells the compiler which other classes use this class.

False; It tells the compiler where it can find classes used by this class.

True or False: Every class has a method called "main".

False; No, you can have classes with different methods.

True or False: A subclass inherits all those constructors of its superclass that are not defined explicitly in the subclass.

False; constructors aren't inherited.

In Java every class extends the library class _______ by default.

Object

True or False: Fields of a class are usually declared "private".

True

A subclass does not inherit ________

constructors

What's a CRC card?

index card that gives basic, informal description of a class: name, key responsibilities of objects, collaborators (other classes this class depends on)

If void is in a method's header it means that ________

the method does not return a value Ex: main

What does it mean when a method is declared static?

That method belongs to a class as a whole, not to any particular object of that class.

What is the IS-A relationship between objects?

an object of a subclass IS-A object of its superclass

What are setters/modifiers?

methods that set the values of private fields

A subclass inherits all the ______ & _______ of its superclass.

methods, fields

True or False: The name of a class in Java must be the same as the name of its source file. (excluding the extension ".java")

True; A class cannot have a different name than the source file.

True or False: A Java program may have as many classes as necessary.

True; You can have an infinite number of classes in a Java program.

True or False: An object has to be created before it can be used.

True; You can't use something that doesn't exist.

True or False: The names of classes are case-sensitive.

True; You must use the correct case when naming classes.

True or False: A subclass inherits all the fields and public methods of its superclass.

True; a subclass does inherit all the fields and public methods.