• a) Take a look at ExtractNames.java - read the code and comments, and fix the program by INSERTING the missing code (refer to the online documentation for the String class, and its methods).
• b) Modify this program so that it reads a String from the user in the following format "First Last", i.e. first name followed by a space followed by last name, then extracts and prints the first and last names.

• a) Modify ChangeCounter so that the output is printed in currency format. (Use the predefined class NumberFormat. Refer to Chapter 3 example Purchase.java.)
• b) Modify the Computation program so that the output of the average is rounded to 4 decimal places. At least one digit should be printed to the left of the decimal point; it should be 0 if the int portion is 0. (Use the predefined class DecimalFormat. Refer to Chapter 3 example CircleStats.java.)
• c) Format the output of your ForceConverter program so that it is rounded to 8 decimal places.

• You may solve this by modifying the following program which is incomplete (but only requires two additional statements): ClockExercise.java

Test your program on different degrees; if your program is working correctly, the result should be 1 each time (pythagorean trigonometric identity). Refer to the Java API for the Math class, i.e. Math methods sin, cos, pow, toRadians, round. If there is a logical error (i.e. the result is not correct), use the debugger to step through your program; it will be easier if you decompose the problem into subproblems rather than computing the entire formula in one statement.

• a) Modify DrawFiguresUpdated.java by defining a new method named drawHouse, and calling this method from main. Your new method drawHouse draws the house by invoking (calling) the given methods to draw a cone, and a box.
• b) Modify DrawFiguresUpdated.java by passing an additional parameter to the method drawRocket() that stores the country as a 2 character String (e.g. "US") and includes the specified country on the rocket. Draw 2 rockets, one with "US" and another with "RU", by having your main method call the same drawRocket() method twice.
• c) Modify ModularSnowman so that it draws two snowmen side by side. Try to do so in a way that minimizes redundant code. (Read and understand the definition and use (calling/invocation of) the generateSnowman method; you may add an additional call to the generateSnowman method in order to generate a second snowman.)
• d) Design and implement an application that draws your own picture that is made up of repeating components. Use methods. Define a method that is called multiple times in order to draw multiple components of the same kind, like you did to draw multiple snowmen.
• e) 10/15: Read and understand LbsToKgsWithMethods.java. Rewrite your ForceConverter program (exercise 8) with methods. Trace your program with the debugger: set a breakpoint (in BlueJ, click on a statement in your program, then click Tools...Set breakpoint) then run your main method one step at a time (stepping into your methods, and looking at how the variables change).

• Practice writing code that calls methods, i.e. invokes methods: Codelab - Chapter 4 - Methods - Invocation
  • 20643, 20644, 20645, 20646, 20647, 20648, 20649
• Practice writing code that defines methods: Codelab - Chapter 4 - Methods - Definition
  • 20651, 20652, 20654 (you may call method max of Math class), 20655, 20656
  • You may SKIP for now the following exercises in this section: 20653, 20657, 20658, 20659

Modify your solution to exercise 18 part a, so that there are 2 classes: 1) PrimitiveFiguresLibrary.java, a class with methods that draw primitive shapes such as a cone and a box, and 2) a class named House, whose main method draws two houses, by calling twice a method drawHouse (defined in the same class), which calls methods drawCone() and drawBox() of PrimtiveFiguresLibrary.

Working with an object of our own blueprint class (Circle, in this example). Read and understand a solution to quiz problem 6 (CircleStats.java). Redo this program in an object-based way, i.e. using a blueprint or data class (Circle.java) to create a Circle object, and invoke methods on this object to compute the area and circumference. You may solve this by modifying driver class CircleStats1.java and blueprint class Circle.java, by inserting code in the lines indicated by asterisks.

• Another idea: read and understand Don't fear the OOP by Jos Claerbout (thanks to former student Philip for sending the link). Implement at least two of the classes: a Driver (e.g. Gunfight) and a Blueprint (e.g. WesternTown); encapsulate the objects; make each attribute private. Customize the given examples, i.e. by modifying the classes and attributes, according to the "novel" you want to write.

• a) Codelab: Chapter 4 - Objects - Constructors (exercises 20633, 20634, 20635, 20636, 20637) and Aliases (exercises 20516, 20517, 20518).
• b) I will go over this at the beginning of the lab:
  • In groups of 2, you will call/invoke methods and define methods, using either Jeroo or Finch. The theme and level of difficulty are similar for both: writing code to get a Jeroo or Finch from a starting location to a destination. Choose either the Jeroo exercises or Finch exercises. When you are done, raise your hand and show me your solution; also let me know why you selected the option you did.
• c) 10/24: Review the example from class: RollingDice which uses Die. RollingDice is a driver class whose main method instantiates (i.e. creates) 2 Die objects, then calls the computeSum method which is defined in the Die class. As you review this example, let me know if something is not clear. Define 2 classes (in 2 separate files): 1) a driver class named TestPoint and 2) a blueprint class named Point:
  • TestPoint is a driver class, whose main method instantiates 4 Point objects (e.g.

    Point p1 = new Point (0, 0);
    Point p2 = new Point (4, 3);
    Point p3 = new Point (3, 4);
    Point p4 = new Point (0, 0);
    

    ), then computes and prints the distance between the first 2 points and the distance between the last 2 points (by calling a method calcDistance as follows:

    distance1 = p1.calcDistance (p2); 
    distance2 = p3.calcDistance (p4); 
    

    where p1, p2, p3 and p4 are Point objects, and calcDistance is a method to be defined in the Point class).
  • A Point contains instance data for the x and y coordinates. Define the Point constructor to accept and initialize this data. Include a method to calculate and return the distance from this point to another point.
  • Try writing your driver code first, and writing comments before code.
  • Include a toString() method to return a nicely-formatted String representation of a point, e.g. if a point's x value is 3 and y value is 4, then the toString() method should return the following String: "(3, 4)"; the toString method is defined in your Point class and called (invoked) in your TestPoint class in order to print the output in a readable way, e.g.: The distance between (0, 0) and (3, 4) is 5.
• d)
  • Try writing your driver code first, and writing comments before code. Create two classes, Kennel and Dog, as follows. Kennel is a driver class, whose main method instantiates several Dog objects, then computes and prints their ages in "person years". A Dog contains instance data that represents the dog's name and age. Define the Dog constructor to accept and initialize instance data. Include a method to compute and return the age of the dog in "person years" (seven times the dog's age). Include a toString method that returns a one-line description of the dog. Include getter (accessor) and setter (mutator) methods for the name and age, i.e.

    • public String getName()

    • public double getAge()

    • public void setName(String)

    • public void setAge(double)

• e) 10/29: Add a test case (which consists of an actual result computed by your program and the expected result, i.e. what it should be) to the main method of your Kennel class: After the statement that prints the value returned by computePersonYears(), print the expected result (e.g. "That should have printed 21" assuming the expected result is 21). A test case consists of an actual result and expected result. This exercise will help you understand the testing exercise of hw4. We will go over hw4 further in class.
• f) 10/29: Try writing your driver code first, and writing comments before code. Create two classes, Bookshelf and Book, as follows. Bookshelf is a driver class, whose main method instantiates and prints several Book objects. A Book contains instance data for the title, author, publisher, and copyright date. Define the Book constructor to accept and initialize this data. Include a toString method that returns a nicely formatted, multi-line description of the book. Include getter (accessor) and setter (mutator) methods for one of the attributes, and call these methods from the main method of Bookshelf.

You may choose the Finch or Jeroo exercise:
• Finch: Modify the given Demo program so that it prints a menu of options (e.g. 1 - move, 2 - back up, 3 - turn, 4 - change color) then based on the user's choice, the robot will act accordingly. For some commands, additional info may be needed from the user, e.g. which direction to turn, what color to display.
• Jeroo: Note: this exercise will be alot easier if you design first with a flowchart like we discussed in our 11/5 class. In this exercise, you will give some decision-making ability to a Jeroo object. Write a Jeroo method skip() which will have the final effect of hop(3) but will not make any effective move if there is water or net in any of the spaces in its path (i.e. the 3 squares that it would like to hop, one at a time, in the direction that it is facing). A Jeroo can only hop one square at a time, and can only detect obstacles that are one space away; if it detects an obstacle, have it turn around and go back to its original square. (Your method skip() will need to invoke some of the boolean methods described in the help menu.) Write a method main() that instantiates several Jeroo objects (in different locations and facing different directions), on which the method skip() is invoked. Place objects (such as water, net) on the island, so that when you run your program, you will be convinced that your method skip() works no matter where the Jeroo object is, what direction it is facing, and what is in its path. (You may refer to Jeroo example)

• a) Codelab exercise -> Chapter 5 -> Switch Statement -> 20623
• b) Time permitting, a more challenging exercise using switch statement (consider the restrictions that we discussed): repeat Exercise 27 using a switch statement instead of a nested if.

• We are playing a game today: "Who is the Most Extreme?"(named after the agile software development process Extreme Programming). Wait for explanation of rules before proceeding with the following: How do you compare objects for equality? Two objects are considered equal if and only if they have the same values for all their attributes, e.g. a pair of equal points have the same x and y coordinates.
  • Define a driver class TestGenome that compares Genome objects for equality, as discussed in lecture. Then define an equals method in Genome class, which encapsulates its type (integer) and its dna (String).
  • Modify your Kennel class so that it compares Dog objects for equality. (A pair of equal dogs have the same name and age.)
  • Modify your TestPoint class so that it compares Point objects for equality. (A pair of equal points have the same x and y coordinates.)
  • Time permitting, modify your Bookshelf class so that it compares books for equality.

count-controlled loops
• a) Modify your program that draws 2 pictures (e.g. houses, rockets or snowmen) so that it uses a loop (with 2 iterations). What would you need to change if you wanted the program to draw more than 2 pictures?
• b) Modify your program that reads 3 grades from the user (and computes the average and letter grade) so that it uses a while loop to read the 3 grades. In the loop body, you will just read one grade and update other variables appropriately. The loop header will ensure 3 iterations.
• c) Modify your program in part b so that it asks the user how many grades there are and uses a while loop to read that many grades.
• d) Use a for loop instead of a while loop, for the count-controlled loop you did for part b or c.

• Finch: Modify your Finch solution to exercise 28 so that it validates each input (define an isValid method that is called within a do loop) and allows the user to continue until they decide to quit (add a quit option to your menu). You may refer to this program that uses methods to read and validate input.
• Jeroo: Download "Intermediate Activity: Hurdle Race" from Jeroo's website and write a program that allows a Jeroo to "jump over" hurdles consisting of nets (see the Word document that comes with the hurdle race activity for further details). Note: The island may have any number of hurdles (each of which can be any height and any width). Hint: Write a method that jumps one hurdle, and call this method as needed within a loop. Your islands will represent test cases: 1) an island with no hurdles, 2) an island with one hurdle, 3) an island with more than one hurdle...

• Trace the following program assuming the user enters 3 for value and 21 for limit. Draw a table showing the values of relevant variables (value, limit, mult, count) during each iteration of the loop: Multiples.java. As you trace, keep track of the output too, and then check that your predicted output is correct by running the program.
• Trace Stars.java by drawing a table that shows the values of relevant variables (row and star) and keeping track of the output. This program contains a nested for loop, so for each iteration of the outer loop, the inner loop executes in its entirety:

  row	star
  1	1
  2	1
  2	2
  3	1
  3	2
  3	3
  ...	...

• 12/3: Design Exercise.
• 12/3: Given TestGraph.java (driver class), complete the implementation of Graph.java, according to the design. Test your program, according to your test plan, and check the results.
  • 12/3: Improved version (in which the Blueprint class's methods do NOT print and thus are more re-usable; the only printing happens in the driver class which is currently printing to screen but can be modified later to send output elsewhere e.g. to a file, without any change to the Blueprint): Given TestGraph1.java (driver class), complete the implementation of Graph1.java, according to the design. Test your program, according to your test plan, and check the results.

• a) Codelab exercises on arrays
• b) An object-based version of the Computation program: Complete the class Student.java and test it with TestStudent.java.

• 12/5:
  • a) A parameter passing example/exercise. There is another parameter passing tracing exercise in the handout on practice problems on loops and arrays (question 8).
  • b) 3 exercises using arrays (Note: the third part of this exercise is optional because it involves array of objects which will not be on the final exam)