DSA QUIZ 2 WITH COMPLETE
SOLUTIONS
Static - Correct Answers -opposite of instance, same for every instance of class
type of copy of .clone() - Correct Answers -shallow copy
Declare then instantiate: constructor - Correct Answers -ClassName variableName =
new Constructor()
left is declaring and right (constructor) is instantiating
same method - Correct Answers -the order of data type parameters must be different
method(parameters) is its signature
equals and toString methods if you don't write one - Correct Answers -every object has
an equals method but it will only compare reference addresses
every object has a toString method but will print a string of classnamereferenceaddress
(Television@36190af)
have to override to change
inheritance keyword - Correct Answers -extends
everything extends - Correct Answers -object class
which has...
toString
equals
clone
hashCode- returns a unique int for object
can extend - Correct Answers -one class
(one parent from inheritance)
Composition vs Inheritance - Correct Answers -composition is what an object is made
up of (data and methods/states and behaviors)
class determines its state and behavior (has a)
inheritance is when a class inherits from another class (is a)
abstract method, final/static - Correct Answers -abstract method cannot be final or static
or private
constructor cannot be abstract
abstract method cannot be called
, how to declare as abstract - Correct Answers -after accessModifier/before class or
dataType
accessModifier abstract returnType methodName( argument list ); no body for method
Subclasses of abstract Classes - Correct Answers --A subclass of an abstract class can
implement all, some, or none of the abstract methods.
-If the subclass does not implement all of the abstract methods, it must also be declared
as abstract.
Overloading vs Overriding - Correct Answers -Methods in the same class which have
the same name but have different parameters.
Parameters may be of a different type and/or the number of parameters may be
different (can be different order)
VS
Methods, one in a parent class and the other in a child class which have the same
name and
parameters. The method in the child class is invoked rather than the parent class
method.
public vs private vs protected - Correct Answers -public: anyone
private: only class
protected: everything except world
friendly: class and package, not sub or world
if have a null validation for setting a value... - Correct Answers -provide an else for a
default empty string
instantiate vs declare abstract class - Correct Answers -can declare as abstract class
but not instantiate
abstract on left, inherited nonabstract on right
Polymorphism - Correct Answers -an object of a subclass is also an object of any of its
superclasses
superclass = subclass - Correct Answers -super has to be on left if you're going to mix
(can be switched but has to be casted)
(because reference type if what its declared as and reference type is the highest it can
reach but if you're trying to assign a super class to a declared sub class, it can't reach
that high)
but then you can't call unique sub methods on object since it is type of super (method
used is determined by object its pointed too but won't compile if reference type doesn't
also have that)
SOLUTIONS
Static - Correct Answers -opposite of instance, same for every instance of class
type of copy of .clone() - Correct Answers -shallow copy
Declare then instantiate: constructor - Correct Answers -ClassName variableName =
new Constructor()
left is declaring and right (constructor) is instantiating
same method - Correct Answers -the order of data type parameters must be different
method(parameters) is its signature
equals and toString methods if you don't write one - Correct Answers -every object has
an equals method but it will only compare reference addresses
every object has a toString method but will print a string of classnamereferenceaddress
(Television@36190af)
have to override to change
inheritance keyword - Correct Answers -extends
everything extends - Correct Answers -object class
which has...
toString
equals
clone
hashCode- returns a unique int for object
can extend - Correct Answers -one class
(one parent from inheritance)
Composition vs Inheritance - Correct Answers -composition is what an object is made
up of (data and methods/states and behaviors)
class determines its state and behavior (has a)
inheritance is when a class inherits from another class (is a)
abstract method, final/static - Correct Answers -abstract method cannot be final or static
or private
constructor cannot be abstract
abstract method cannot be called
, how to declare as abstract - Correct Answers -after accessModifier/before class or
dataType
accessModifier abstract returnType methodName( argument list ); no body for method
Subclasses of abstract Classes - Correct Answers --A subclass of an abstract class can
implement all, some, or none of the abstract methods.
-If the subclass does not implement all of the abstract methods, it must also be declared
as abstract.
Overloading vs Overriding - Correct Answers -Methods in the same class which have
the same name but have different parameters.
Parameters may be of a different type and/or the number of parameters may be
different (can be different order)
VS
Methods, one in a parent class and the other in a child class which have the same
name and
parameters. The method in the child class is invoked rather than the parent class
method.
public vs private vs protected - Correct Answers -public: anyone
private: only class
protected: everything except world
friendly: class and package, not sub or world
if have a null validation for setting a value... - Correct Answers -provide an else for a
default empty string
instantiate vs declare abstract class - Correct Answers -can declare as abstract class
but not instantiate
abstract on left, inherited nonabstract on right
Polymorphism - Correct Answers -an object of a subclass is also an object of any of its
superclasses
superclass = subclass - Correct Answers -super has to be on left if you're going to mix
(can be switched but has to be casted)
(because reference type if what its declared as and reference type is the highest it can
reach but if you're trying to assign a super class to a declared sub class, it can't reach
that high)
but then you can't call unique sub methods on object since it is type of super (method
used is determined by object its pointed too but won't compile if reference type doesn't
also have that)
