Except where otherwise noted, the contents of this document are Copyright 2012 Stuart Reges and Marty Stepp.
lab document created by Marty Stepp, Stuart Reges and Whitaker Brand
Goals for today:
Suppose you are given a class named ClockTime
with the following contents:
// A ClockTime object represents an hour:minute time during // the day or night, such as 10:45 AM or 6:27 PM. public class ClockTime { private int hour; private int minute; private String amPm; // Constructs a new time for the given hour/minute public ClockTime(int h, int m, String ap) // returns the field values public int getHour() public int getMinute() public String getAmPm() // returns a String for this time; for example, "6:27 PM" public String toString() ... }
advance
that will be placed inside the ClockTime
class.
The method accepts a number of minutes as its parameter and moves your object forward in time by that amount of minutes.
The minutes passed could be any non-negative number, even a large number such as 500 or 1000000.
If necessary, your object might wrap into the next hour or day, or it might wrap from the morning ("AM") to the evening ("PM") or vice versa.
(A ClockTime object doesn't care about what day it is; if you advance by 1 minute from 11:59 PM, it becomes 12:00 AM.)
ClockTime time = new ClockTime(6, 27, "PM"); time.advance(1); // 6:28 PM time.advance(30); // 6:58 PM time.advance(5); // 7:03 PM time.advance(60); // 8:03 PM time.advance(128); // 10:11 PM time.advance(180); // 1:11 AM time.advance(1440); // 1:11 AM (1 day later) time.advance(21075); // 4:26 PM (2 weeks later)
isWorkTime
that will be placed inside the ClockTime
class.
The method returns true
if the object is a time during the "work day" from 9:00 AM - 5:00 PM inclusive; otherwise false
.
ClockTime t0 = new ClockTime(12, 45, "AM"); // false ClockTime t1 = new ClockTime( 6, 02, "AM"); // false ClockTime t2 = new ClockTime( 8, 59, "AM"); // false ClockTime t3 = new ClockTime( 9, 00, "AM"); // true ClockTime t4 = new ClockTime(11, 38, "AM"); // true ClockTime t5 = new ClockTime(12, 53, "PM"); // true ClockTime t6 = new ClockTime( 3, 15, "PM"); // true ClockTime t7 = new ClockTime( 4, 59, "PM"); // true ClockTime t8 = new ClockTime( 5, 00, "PM"); // true ClockTime t9 = new ClockTime( 5, 01, "PM"); // false ClockTime ta = new ClockTime( 8, 30, "PM"); // false ClockTime tb = new ClockTime(11, 59, "PM"); // false
Suppose you are given a class named Rectangle
with the following contents:
// A Rectangle stores an (x, y) coordinate of its top/left corner, a width and height. public class Rectangle { private int x; private int y; private int width; private int height; // constructs a new Rectangle with the given x,y, width, and height public Rectangle(int x, int y, int w, int h) // returns the fields' values public int getX() public int getY() public int getWidth() public int getHeight() // returns a string such as {(5,12), 4x8} public String toString() ... }
union
that will be placed inside the Rectangle
class. The method accepts another rectangle r as a parameter and turns the current rectangle into the union of itself and r; that is, modifies the fields so that they represent the smallest rectangular region that completely contains both this rectangle and r.
Rectangle rect1 = new Rectangle(5, 12, 4, 6); Rectangle rect2 = new Rectangle(6, 8, 5, 7); Rectangle rect3 = new Rectangle(14, 9, 3, 3); Rectangle rect4 = new Rectangle(10, 3, 5, 8); rect1.union(rect2); // {(5, 8), 6x10} rect4.union(rect3); // {(10, 3), 7x9}
contains
that will be placed inside the Rectangle
class.
The method accepts integers for x and y as parameters and turns true
if that x/y coordinate lies within this rectangle.
The edges are included; for example, a rectangle with x=2, y=5, width=8, height=10 will return true
for any point from (2, 5) through (10, 15) inclusive.
public class ClassName extends SuperClass { ... }
super
keyword:super.methodName(parameters);
Car
and Truck
public class Car { public void m1() { System.out.println("car 1"); } public void m2() { System.out.println("car 2"); } public String toString() { return "vroom"; } } |
public class Truck extends Car { public void m1() { System.out.println("truck 1"); } } |
Truck mycar = new Truck(); System.out.println(mycar); // vroom mycar.m1(); // truck 1 mycar.m2(); // car 2
Car
and Truck
revisited
public class Car { public void m1() { System.out.println("car 1"); } public void m2() { System.out.println("car 2"); } public String toString() { return "vroom"; } } |
public class Truck extends Car { public void m1() { System.out.println("truck 1"); } public void m2() { super.m1(); } public String toString() { return super.toString() + super.toString(); } } |
Truck
code changes as shown above.
What is the output now?
Truck mycar = new Truck(); System.out.println(mycar); // vroomvroom mycar.m1(); // truck 1 mycar.m2(); // car 1
MonsterTruck
MonsterTruck
that has the behavior below.
Test by running AutoMain
.
/
.
MonsterTruck bigfoot = new MonsterTruck(); bigfoot.m1(); // monster 1 bigfoot.m2(); // truck 1 / car 1 System.out.println(bigfoot); // monster vroomvroom
Employee
and has the methods
getHours
,
getSalary
,
getVacationDays
, and
getVacationForm
.
Marketer
Marketer
to accompany the other employees.
Marketers make $50,000 ($10,000 more than general employees),
and they have an additional method named advertise
that prints "Act now, while supplies last!"
super
keyword to interact with the Employee
superclass as appropriate.
Janitor
Janitor
to accompany the other employees.
Janitors work twice as many hours (80 hours/week),
they make $30,000 ($10,000 less than others),
they get half as much vacation (only 5 days),
and they have an additional method named clean
that prints "Workin' for the man."
super
keyword to interact with the Employee
superclass as appropriate.
HarvardLawyer
HarvardLawyer
to accompany the other employees.
Harvard lawyers are like normal lawyers, but they make 20% more money than a normal lawyer,
they get 3 days more vacation, and they have to fill out four of the lawyer's forms to go on vacation.
That is, the getVacationForm
method should return "pinkpinkpinkpink"
.
Lawyer
's vacation form ever changed, the HarvardLawyer
's should as well.
For example, if Lawyer
's vacation form changed to "red"
,
the HarvardLawyer
's should return "redredredred"
.)
super
keyword to interact with the Employee
superclass as appropriate.
Suppose you are given a class named Point
with the following contents:
// A Point represents a 2-D (x, y) position with integer coordinates. public class Point { private int x; private int y; public Point() // (0, 0) public Point(int x, int y) public int getX() // return field values public int getY() public double distanceFromOrigin() // distance from (0, 0) public double distance(Point other) // distance from another point public void setLocation(int x, int y) // set x/y to the given values public void translate(int dx, int dy) // shift x/y by the given amounts public String toString() // string e.g. "(4, -7)"
manhattanDistance
Add the following method to the Point
class:
public int manhattanDistance(Point other)
Returns the "Manhattan distance" between the current Point
object and the given other Point
object.
The Manhattan distance refers to how far apart two places are if the person can only travel straight horizontally or vertically, as though driving on the streets of Manhattan.
In our case, the Manhattan distance is the sum of the absolute values of the differences in their coordinates; in other words, the difference in x plus the difference in y between the points.
Click on the check-mark above to try out your solution in Practice-it!
(Write just the new method, not the entire Point
class.)
flip
Add the following method to the Point
class:
public void flip()
Negates and swaps the x/y coordinates of the Point
object.
For example, if an object pt
initially represents the point (5, -3), after a call of pt.flip();
, the object should represent (3, -5).
If the same object initially represents the point (4, 17), after a call to pt.flip();
, the object should represent (-17, -4).
Test your code in Practice-It! or by running the PointMain
program.
quadrant
Add the following method to the Point
class:
public int quadrant()
Returns which quadrant of the x/y plane this Point
object falls in.
Quadrant 1 contains all points whose x and y values are both positive.
Quadrant 2 contains all points with negative x but positive y.
Quadrant 3 contains all points with negative x and y values.
Quadrant 4 contains all points with positive x but negative y.
If the point lies directly on the x and/or y axis, return 0.
(Test your code in Practice-It! or by running the PointMain
program.)
Suppose you are given a class named BankAccount
with the following contents:
// A BankAccount keeps track of a user's money balance and ID, // and counts how many transactions (deposits/withdrawals) are made. public class BankAccount { private String id; private double balance; private int transactions; // Constructs an object with the given id/balance and 0 transactions. public BankAccount(String id, double balance) public double getBalance() public String getID() public String getTransactions() // Adds amount to balance if between 0-500. Also counts as 1 transaction. public void deposit(double amount) // Subtracts amount from balance if user has enough money. Counts as 1 transaction. public void withdraw(double amount) ... }
transactionFee
to go in the BankAccount
class.
It takes a fee (real number) parameter and applies the fee to all past transactions.
The fee is applied once for the first transaction, 2x for the second, 3x for the third, etc.
These fees are subtracted from the account's balance.
true
.
If not, the balance is 0.0 and it returns false
. For example:
BankAccount savings = new BankAccount("Jimmy", 0.00); savings.deposit(10.00); savings.deposit(50.00); savings.deposit(10.00); savings.deposit(70.00); // balance = $140, with 4 transactions savings.transactionFee(5.00); // deducts $5+10+15+20; balance = $90; returns true savings.transactionFee(10.00); // deducts $10+20+30+40; balance = $0; returns false
transfer
that moves money from this bank account to another account.
The method takes two parameters: a BankAccount
to accept money, and a real number for the amount to transfer.
There is a $5.00 fee for transferring, to be deducted from the current account's balance.
BankAccount ben = new BankAccount("Benson", 90.00); BankAccount mar = new BankAccount("Marty", 25.00); ben.transfer(mar, 20.00); // ben $65, mar $45 (ben loses $25, mar gains $20) ben.transfer(mar, 10.00); // ben $50, mar $55 (ben loses $15, mar gains $10) ben.transfer(mar, -1); // ben $50, mar $55 (no effect; negative amount) mar.transfer(ben, 39.00); // ben $89, mar $11 (mar loses $44, ben gains $39) mar.transfer(ben, 50.00); // ben $95, mar $ 0 (mar loses $11, ben gains $ 6) mar.transfer(ben, 1.00); // ben $95, mar $ 0 (no effect; no money in account) ben.transfer(mar, 88.00); // ben $ 2, mar $88 (ben loses $93, mar gains $88) ben.transfer(mar, 1.00); // ben $ 2, mar $88 (no effect; can't afford fee)
TimeSpan
Define a class named TimeSpan
.
A TimeSpan
object stores a span of time in hours and minutes (for example, the time span between 8:00am and 10:30am is 2 hours, 30 minutes).
The minutes should always be reported as being in the range of 0 to 59.
That means that you may have to "carry" 60 minutes into a full hour.
To solve this problem, you may want to refer to the lecture slides about the syntax for constructors.
See the Practice-It link above for a full description of the class and the methods/constructors it should have.
Circle
Define a class named Circle
.
A Circle
object stores a center point and a radius.
See the Practice-It link above for a full description of the class and the methods/constructors it should have. You can also test your class in Practice-It.
If you finish all the exercises, try out our Practice-It web tool. It lets you solve Java problems from our Building Java Programs textbook.
You can view an exercise, type a solution, and submit it to see if you have solved it correctly.
Choose some problems from the book and try to solve them!