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Java OOP
SHORT
ANSWER QUESTIONS
AGGREGATION
QUESTIONS
Fill the blanks and short answer questions.
Solutions are at the bottom of this document.
a)
______________
is the concept of having objects be instance variables inside other
objects. So, objects can be made up of
different objects.
b)
For
each of the following classes showing their instance variables, state whether
there is Aggregation or not.
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A)
public class Point
{
public int x;
public int y;
//Nothing else shown.
}
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B)
public class Address
{
private int number;
private String street;
private int apt;
//Nothing else shown.
}
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C)
public
class Ingredient
{
public String name
public double amount;
public String unit;
//Nothing else shown.
}
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D)
public
class Trio
{
private byte n1;
private byte n2;
private byte n3;
//Nothing else shown.
}
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E)
public class Recipe
{
public Ingredient ing1;
public Ingredient ing2;
public Ingredient ing3;
public Ingredient ing4;
public Ingredient ing5;
//Nothing else shown.
}
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F)
public class Light
{
public boolean on
public int brightness;
//Nothing else shown.
}
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c)
How
can we easily tell if an instance variable (or any variable really) is a
primitive data type or an object?
d)
Complete
the following Line constructors given the Point class on the right.
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public
class Line
{
public Point p1;
public Point p2;
public Line(Point tp1, Point tp2)
{
}
public Line(int x1, int y1, int x2, int
y2
{
}
}
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public
class Point
{
public int x;
public int y;
public Point(int tx, int ty)
{
x = tx;
y = ty;
}
}
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e)
Consider
the Name and Address classes below and complete the Person class’
constructors.
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public
class Name
{
public String first;
public String mid;
public String last;
public Name(String f, String m,
String l)
{
first = f;
mid = m;
last = l;
}
}
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public
class Address
{
public int number;
public String street;
public String town;
public String province;
public String postalCode;
public Address(int n, String s, String
t, String p, String pc)
{
number = n;
street = s;
town = t;
province = p;
postalCode = pc;
}
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public
class Person
{
public Name n;
public Address a;
public Person(Name n, Address a)
{
}
public Person(String f, String m, String
l, int n, String s, String t, String p, String pc)
{
}
}
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f)
Assume
the above Name and Address classes are changed so that all instance variables
are private and that there is a get method for each one.
1) Show the entire implementation of the getProvince() method in Address.
2)
Assume the Person class’ instance variables are set to private. Show the entire implementation of the
getAddress() method.
3)
If we wanted to have a getPostalCode() method in the Person class, how would
you implement that?
SOLUTIONS
Click here.
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