Computer Science E-50a: Introduction to Computer Science Using Java, I Handout #7 part 2

Transcription

1 Computer Science E-50a: Introduction to Computer Science Using Java, I Handout #7 part 2 part 2 These problems are due prior to the start of lecture on Monday night, March 31. Part A The Reading You may need to browse through the first 4 or 5 chapters in the Savitch textbook (or another Java reference book, if you have one). Now solve the following problems. Part B Pencil-and-Paper Exercise (10 points total) Don t use the computer in solving the following problem. [1] 10 points A certain charity designates donors who give more than $1,000 as Benefactors; those who give $500 to $999 as Patrons; those who give $100 to $499 as Supporters; those who give $15 to $99 as Friends; and those who give less than $15 as Cheapskates. Write a nested if-else statement (or statements) that, given the amount of a contribution, outputs the correct designation for that contributor. Assume an int variable named donationamount has already been declared and initialized with an appropriate value for your use. Spring 2003 Dr. S. J. Eigen

2 Computer Science E-50a: Introduction to Computer Science Using Java, I Page 2 Part C Programming Problems (55 to 70 points) Solve the following problems using the computer! You must turn in computer printouts for these problems, as well as submit your work electronically via the UNIX system. We will demonstrate how to do this in lecture, and provide you with documentation in Part D of this handout. Be sure you use the precise file names shown in the problem descriptions when you write your own solutions! [2] 10 points (file Temperature.java) Write a Java program that prompts the user for a temperature between -20 and 110 degrees fahrenheit, and then tells the user what sport[s] can be played, according to the chart below. (Don't print the chart!) Swimming: >= 75 degrees Tennis: 60 < temperature <= 85 Skiing: 10 < temperature <= 32 Checkers: <= 10 degrees

3 Computer Science E-50a: Introduction to Computer Science Using Java, I Page 3 Soccer: 32 < temperature <= 70 Here are two examples to illustrate what your program should look like in action: OK, mate, what's the temperature outside? 78 Looks good for... swimming tennis OK, mate, what's the temperature outside? 10 Looks good for... checkers Be sure to test your program out on a variety of (insightfully chosen) input values, and not just the ones shown above. [3] 15 points (file Triangle.java) Write a Java program that produces the output Your program must not, of course, consist entirely of System.out.print statements! Use for loops.

4 Computer Science E-50a: Introduction to Computer Science Using Java, I Page 4 [4] 15 points (file Rocks.java) Officials at American embassies around the world are on alert to keep some statistics on the number of rocks thrown at their buildings each day. At the moment, embassy officials are interested in finding out only the average number of rocks thrown over a period of n days. They have asked for your help in writing a Java program to do this. Write a program named Rocks that computes the average of n numbers, where n is unknown when you write the program. Your program shall begin by asking the user for the value of n the number of values to be averaged up; your program will then allow the user to input n values, and finally compute (and print) their average. Your program should not allow the user to input a value for n that is smaller than 1. Your program should not allow the user to input a number smaller

5 Computer Science E-50a: Introduction to Computer Science Using Java, I Page 5 than 1 for the number of days; if the user does, he or she should be warned, and then given another chance. Here are two sample runs to illustrate exactly how your program should appear in operation: How many rock-throwing days do you want averaged up? 4 OK -- Please start typing them in, one per line: How many rocks were thrown on day number 1? 2 How many rocks were thrown on day number 2? 9 How many rocks were thrown on day number 3? 3 How many rocks were thrown on day number 4? 6 There were an average of 5.00 rocks thrown per day! Here's another example illustrating program execution: How many rock-throwing days do you want averaged up? -2 Don't be ridiculous! Negative numbers are impossible! How many rock-throwing days do you want averaged up? 2 OK -- Please start typing them in, one per line: How many rocks were thrown on day number 1? 3 How many rocks were thrown on day number 2? 5 There were an average of 4.00 rocks thrown per day! For two points of extra credit, error-check the individual values typed for each day so that impossible numbers of rocks cannot be input. [5] 15 points (file Pyramid.java) Write a Java program that produces the output * *** ***** ******* ********* Design the program in such a way that it will be easy to enlarge the figure to 10 rows and 19 columns (use constants final ints or

6 Computer Science E-50a: Introduction to Computer Science Using Java, I Page 6 static final ints and nested for loops). [6] For graduate-credit students only 10 points (file BabySitter.java) Undergraduate-credit students may attempt this problem for extra credit. This problem is required for all graduate-credit students. It s harder than it looks! Write a Java program that calculates how much to pay the baby-sitter. Although the problem sounds simple, it s trickier than it appears. Read on carefully! Assume that the starting time for the baby-sitter is somewhere between 6 PM and 11 PM; and that the ending-time is somewhere

7 Computer Science E-50a: Introduction to Computer Science Using Java, I Page 7 between 9 PM and 4 AM. The only input to your program will be 4 numbers. The starting time is expressed as hours and minutes, and the ending time is also expressed as hours and minutes. For example, if the baby sitter works from 7:45 PM until 1:12 AM, then the input to your program should look like the following: At what HOUR did the baby-sitter start work? 7 At what MINUTE did the baby-sitter start work? 45 At what HOUR did the baby-sitter finish working? 1 At what MINUTE did the baby-sitter finish working? No other form of input is acceptable! Also, no other information can be input to the program. The output from your program should be the amount of money to be paid to the baby-sitter. The pay scale is: $3.50 per hour for 6 PM until 8 PM; $4.20 per hour from 8 PM until midnight; and $5.00 an hour after midnight. Use constants (final floats or doubles) for these three pay scales. Your program should be a tiny bit dummy-proof. If the user types input values that either are outside of the allowable range of possible working hours, or if the starting time is later than the ending time then your program should print an appropriate error message, and halt!

8 Computer Science E-50a: Introduction to Computer Science Using Java, I Page 8 [7] For extra credit 5 points (file Matryoshka.java) A factory which makes Matryoshka dolls is run by a rather sadistic fellow. The dolls are made in 10 sizes, #1 being the smallest, and #10 the largest. The dolls are sold as sets, with dolls inside dolls, inside dolls. As workers finish painting dolls, they (the dolls, not the workers) are placed on a conveyer belt in random order. The assemblers, waiting at the end of the line, have been told that they must pick up the dolls in the order in which they arrive. The workers are to insert their current set inside each new doll, making a larger set. If the new doll isn't big enough they must begin a new set. The poor customer who buys a doll with nothing inside is simply out of luck. Write a program which prompts for, and reads a series of 20 doll sizes. The program should announce each time a new set is started. After all 20 sizes have been entered, the program should report the total number of sets and the number of dolls in the largest set. Here s an example to illustrate what your program should look like in action:

9 Computer Science E-50a: Introduction to Computer Science Using Java, I Page 9 Execution of program: Please type the 20 doll sizes: Next doll size: 2 -- new set started Next doll size: 3 Next doll size: 5 Next doll size: 4 -- new set started Next doll size: 6 Next doll size: 8 Next doll size: 1 -- new set started Next doll size: 9 Next doll size: 10 Next doll size: 3 -- new set started Next doll size: 5 Next doll size: 2 -- new set started Next doll size: 8 Next doll size: 10 Next doll size: 9 -- new set started Next doll size: 3 -- new set started Next doll size: 5 Next doll size: 7 Next doll size: 9 Next doll size: 10 There are 7 sets in all. The largest set has 5 dolls. (see for a cool website done last year by an Extension School student for a multimedia class)

10 Computer Science E-50a: Introduction to Computer Science Using Java, I Page 10 [8] For extra credit (5 points) (file BigH.java) Write a Java program that reads a number say n from the keyboard and types out a block letter H on the screen with sides of size n, like these: *** *** *** *** *** *** ********* ********* ********* *** *** *** *** *** *** ** ** ** ** ****** ****** ** ** ** ** * * *** * * The figures shown above are the output that would be produced if the numbers typed in were 3, 2 and 1, respectively. Your program should ask politely for the number to be typed in; make sure it isn t too large or too small to be meaningful, and then print the corresponding H. You should use at least 10 for the maximum allowable size.

11 Computer Science E-50a: Introduction to Computer Science Using Java, I Page 11 Part D Procedures for Submitting Java Programs (from the course website) 1) Before beginning the programming assignment of a problem set, you should create a directory in your account for that problem set, and do the work for that problem set in that directory. The following sequence of commands will do this for unit2 (change the number for later assignments -- everything else will remain the same): [is01] ~> cd [is01] ~> mkdir unit2 [is01] ~> cd unit2 [is01] ~/unit2> % This makes the new directory, and then switches you into it. Note that the characters in appearing square brackets may look different 2) Now, type in, compile, and debug your programs. You'll end up with a bunch of files, some with a '.java' suffix and some with '.class' suffix. 3) Once you're ready to turn in your programs, use the 'script' command to generate demo output. If your source file is "Rocks.java," you should name your script file "Rocks.out", so we can tell which program it is the demo for! Here's how it works: at the Unix prompt type, the following (the name "Rocks.out" is just an example): [is01] ~/unit2> % script -a Rocks.out From this point on, until you type an 'exit' command at the Unix prompt, EVERYTHING THAT APPEARS ON THE SCREEN ALSO GETS SAVED IN A PRINTABLE FILE NAMED Rocks.out (in this example). Typically, you would run the program several times, with either the sample input given by the handout or your own judiciously selected input. IF THE HANDOUT GIVES SAMPLE INPUT, USE THAT INPUT (at least, you may include more). Once you've finished running the program, end the 'script' session by entering an 'exit' command. 'Exit' commands include: exit, <ctrl>-d, as in [is01] ~> exit...some messages appear: exit, Script done, file is

12 Computer Science E-50a: Introduction to Computer Science Using Java, I Page 12 Rocks.out [is01] ~> Now, you can print out the file "Rocks.out" and hand it in! Easy as pie! Once you have thoroughly tested your code and created "demo output" files, submitting your assignment is easy. There are two parts: (a)hardcopy submission (stapled or black-binder-clipped together -- NOT loose!!, NOT paper-clipped!!): 1. printouts of each program 2. demo output for each program, 3. a summary README file and turn in to your TF's "mailbox" outside Science Center 102) (b) Electronic submission (what we're about to do here). TO SUBMIT ELECTRONICALLY, simply type (at the prompt): [is01] ~> submit cscie50a 21 ~/unit2 The syntax is picky: there are four parts to that command. The first two are easy, just type them in; the remainder require explanation: * submit -- just type this in * cscis1 -- just type this in * the "assignment number" - we will provide this to you for each problem set. 21 is correct for unit 2 part 1, ONLY. FYI: IF a unit 'n's problem set gets broken into two parts, the "assignment numbers" will be n1 and n2 (example: since unit 2 has two parts: the "assignment numbers" will be 21 and 22) * ~/unit2 -- the directory containing the files you're submitting. The wrinkle is that it must be a "full" pathname. Putting the "~/" before the directory name does this for you. unit2 -- the name of the directory containing the files, as created in

13 Computer Science E-50a: Introduction to Computer Science Using Java, I Page 13 your home directory at the top of this handout That's it! BUT... it will only work if you've fully and correctly completed steps 1-3 above. If you have trouble, reread these instructions to make sure you've done everything indicated above. If all's well, you'll see a few messages, then a message stating that submission was successful. [is01] ~> submit cscis1 21 ~/unit2 Ok, submitting the files in /home/m/o/studentname/unit2 Creating temporary directory /usr/lsys/submit/ studentname... Copying assignment files to /usr/lsys/submit/ studentname... Submitting cscis1 assignment Temporary files removed. Successful submission! [is01] ~> By the way, it's OK TO RE-SUBMIT revised versions of programs. The 'submit' program will notice that you've already submitted, and will cautiously let you re-submit, prompting you about proceeding. IF YOU RE-SUBMIT, NOTE THE FOLLOWING: * You must ALSO re-submit printouts of BOTH PROGRAM AND MATCHING DEMO RUNS! The Teaching Fellows work mainly from the hardcopy! * CLEARLY MARK THE NEW VERSION AS "REVISED VERSION - PROB SET 'X', PROBLEM 'N'" or similar... and your Teaching Fellow to let him/her know! * MAKE SURE THAT ELECTRONIC AND HARDCOPY SUBMISSIONS MATCH! If you resubmit, you'll see something like this: [is01] ~> submit cscis1 21 ~/unit2 You have already submitted cscis1 assignment 21: -rw studentname extlib 2010 Feb 20 17:10 /home/l/i/libs1/submit/asst21/studentname.tgz Do you want replace your submission with the files currently in:

14 Computer Science E-50a: Introduction to Computer Science Using Java, I Page 14 /home/m/o/morris/unit2 Please enter y or n: y Your existing submission has been put aside as a backup. It will be put back should problems be encountered with the submission you are doing now. However, if the program terminates before you see either: "Successful submission!" or "Unsuccessful submission!" then you will have to run 'submit' again. Ok, submitting the files in /home/m/o/morris/unit2 Creating temporary directory /usr/lsys/submit/morris... Copying assignment files to /usr/lsys/submit/morris... Submitting cscie50b assignment Temporary files removed. Successful submission! [is01] ~> After 'submitting' as above, you should print out your files so they can be turned in to your Teaching Fellow. To print at the Science Center, type (at the prompt): [is01] ~> lpr FileName.java This comes out on the (free) line printer in the Science Center basement terminal room (to the left at the bottom of the stairs), IF IT STILL EXISTS... Near the Help Desk in the Science Center Terminal Room, are a rack of helpful handouts, including one describing how to print on the laser printers in the Science Center (costs 5 cents per page). Laser printing is free at the 53 Church St. labs. YOU MAY, OF COURSE, DOWNLOAD AND PRINT EVERYTHING ON YOUR OWN PRINTER!