handout #12

CSE143—Computer Programming II

Programming Assignment #4

due: Thursday, 7/14/05 (Bastille Day), 9 pm

(courtesy of Stuart Reges)

This assignment will give you practice with queues. You are going to implement a class that computes all the primes up to some integer n inclusive.  The technique you are to use was developed by a Greek named Eratosthenes who lived in the third century BC.  The technique is known as the Sieve of Eratosthenes.

The algorithm is described by the following pseudocode:

create a queue and fill it with the consecutive integers 2 through n inclusive.
create an empty queue to store primes.
do {
    obtain the next prime by removing the first value in the queue of numbers.
    put the next prime into the queue of primes.
    go through the queue of numbers, eliminating numbers divisible by the next prime.
} while (the next prime < sqrt(n))
all remaining values in numbers queue are prime, so transfer them to primes queue

You are to use the Queue interface discussed in lecture (handout #11).  When you want to construct a Queue object, you should make it of type LinkedQueue.  These classes will be included in the zip file for the assignment.

You should define a class called Sieve with the following public methods:

Method

Description

Sieve()

Constructs a sieve object.

void computeTo(int n)

Computes all primes up to n inclusive.  Throws an IllegalArgumentException if n is less than 2.

void reportResults()

Reports the primes to System.out.  Throws an IllegalStateException if the computeTo method has not yet been called with a valid argument.

int getMax()

Returns the argument passed in the last call on computeTo.  Throws an IllegalStateException if the computeTo method has not yet been called with a valid argument.

int getCount()

Returns the number of primes found in the last call on computeTo.  Throws an IllegalStateException if the computeTo method has not yet been called with a valid argument.

Your reportResults method should print the maximum n used and should then show a list of the primes, 12 per line with a space after each prime.  Notice that there is no guarantee that the number of primes will be a multiple of 12.  The calls on reportResults must exactly reproduce the format of the sample log.  The final line of output that appears in the log reporting the percentage of primes is generated by the main program, not by the call on reportResults.

Even though you will be using a LinkedQueue to write this program, you should use variables of type Queue.  It should be possible for someone to replace the call on the LinkedQueue constructor with a call on the constructor of another class that implements the Queue interface and the rest of your code should work without modification.

You must guarantee that your object is never in a corrupt state.  For example, your sieve object might be asked to compute up to one value of n and then asked to compute up to a different value of n without a call on reportResults ever being made.  Similarly, your object might be asked to compute up to some value of n and then be asked to reportResults more than once.  Each call on reportResults, getMax and getCount should behave appropriately given the previous call on computeTo, no matter how often they are called or in what order.  Finally, notice that if reportResults, getMax or getCount are called before a valid call on computeTo, they throw an exception to indicate that the operation is not legal given the object’s state.

The zip file for this assignment includes a file SieveMain.java that constructs a sieve object and makes calls on it based on values entered by the user.  You can use this program to test your class, but keep in mind that it does not test the internal consistency of your object.

In terms of correctness, your class must provide all of the functionality described above.  In terms of style, we will be grading on your use of comments, good variable names, consistent indentation and good coding style to implement these operations.  Remember that you will lose points if you declare variables as data fields that can instead be declared as local variables.

You MUST name your file Sieve.java and turn it in electronically from the “assignments” link on the class web page.  A collection of files needed for the assignment is included on the web page as ass4.zip.  You will need to have Queue.java, LinkedQueue.java and Scanner.java all in the same directory as your Sieve.java in order to run SieveMain.

Main program SieveMain.java

// Stuart Reges

// 4/18/05

//

// This program computes all the prime numbers up to a given integer n.  It

// uses the classic "Sieve of Eratosthenes" to do so.

 

public class SieveMain {

    public static void main(String[] args) {

        System.out.println("This program computes all prime numbers up to a");

        System.out.println("maximum using the Sieve of Eratosthenes.");

        System.out.println();

        Scanner console = new Scanner(System.in);

        Sieve s = new Sieve();

        for(;;) {

            System.out.print("Maximum n to compute (0 to quit)? ");

            int max = console.nextInt();

            if (max == 0)

                break;

            System.out.println();

            s.computeTo(max);

            s.reportResults();

            int percent = s.getCount() * 100/s.getMax();

            System.out.println("% of primes = " + percent);

            System.out.println();

        }

    }

}

Log of Execution (user responses underlined)

This program computes all prime numbers up to a

maximum using the Sieve of Eratosthenes.

 

Maximum n to compute (0 to quit)? 20

 

Primes up to 20 are as follows:

2 3 5 7 11 13 17 19

% of primes = 40

 

Maximum n to compute (0 to quit)? 100

 

Primes up to 100 are as follows:

2 3 5 7 11 13 17 19 23 29 31 37

41 43 47 53 59 61 67 71 73 79 83 89

97

% of primes = 25

 

Maximum n to compute (0 to quit)? 500

 

Primes up to 500 are as follows:

2 3 5 7 11 13 17 19 23 29 31 37

41 43 47 53 59 61 67 71 73 79 83 89

97 101 103 107 109 113 127 131 137 139 149 151

157 163 167 173 179 181 191 193 197 199 211 223

227 229 233 239 241 251 257 263 269 271 277 281

283 293 307 311 313 317 331 337 347 349 353 359

367 373 379 383 389 397 401 409 419 421 431 433

439 443 449 457 461 463 467 479 487 491 499

% of primes = 19

 

Maximum n to compute (0 to quit)? 1000

 

Primes up to 1000 are as follows:

2 3 5 7 11 13 17 19 23 29 31 37

41 43 47 53 59 61 67 71 73 79 83 89

97 101 103 107 109 113 127 131 137 139 149 151

157 163 167 173 179 181 191 193 197 199 211 223

227 229 233 239 241 251 257 263 269 271 277 281

283 293 307 311 313 317 331 337 347 349 353 359

367 373 379 383 389 397 401 409 419 421 431 433

439 443 449 457 461 463 467 479 487 491 499 503

509 521 523 541 547 557 563 569 571 577 587 593

599 601 607 613 617 619 631 641 643 647 653 659

661 673 677 683 691 701 709 719 727 733 739 743

751 757 761 769 773 787 797 809 811 821 823 827

829 839 853 857 859 863 877 881 883 887 907 911

919 929 937 941 947 953 967 971 977 983 991 997

% of primes = 16

 

Maximum n to compute (0 to quit)? 5000

 

Primes up to 5000 are as follows:

2 3 5 7 11 13 17 19 23 29 31 37

41 43 47 53 59 61 67 71 73 79 83 89

97 101 103 107 109 113 127 131 137 139 149 151

157 163 167 173 179 181 191 193 197 199 211 223

227 229 233 239 241 251 257 263 269 271 277 281

283 293 307 311 313 317 331 337 347 349 353 359

367 373 379 383 389 397 401 409 419 421 431 433

439 443 449 457 461 463 467 479 487 491 499 503

509 521 523 541 547 557 563 569 571 577 587 593

599 601 607 613 617 619 631 641 643 647 653 659

661 673 677 683 691 701 709 719 727 733 739 743

751 757 761 769 773 787 797 809 811 821 823 827

829 839 853 857 859 863 877 881 883 887 907 911

919 929 937 941 947 953 967 971 977 983 991 997

1009 1013 1019 1021 1031 1033 1039 1049 1051 1061 1063 1069

1087 1091 1093 1097 1103 1109 1117 1123 1129 1151 1153 1163

1171 1181 1187 1193 1201 1213 1217 1223 1229 1231 1237 1249

1259 1277 1279 1283 1289 1291 1297 1301 1303 1307 1319 1321

1327 1361 1367 1373 1381 1399 1409 1423 1427 1429 1433 1439

1447 1451 1453 1459 1471 1481 1483 1487 1489 1493 1499 1511

1523 1531 1543 1549 1553 1559 1567 1571 1579 1583 1597 1601

1607 1609 1613 1619 1621 1627 1637 1657 1663 1667 1669 1693

1697 1699 1709 1721 1723 1733 1741 1747 1753 1759 1777 1783

1787 1789 1801 1811 1823 1831 1847 1861 1867 1871 1873 1877

1879 1889 1901 1907 1913 1931 1933 1949 1951 1973 1979 1987

1993 1997 1999 2003 2011 2017 2027 2029 2039 2053 2063 2069

2081 2083 2087 2089 2099 2111 2113 2129 2131 2137 2141 2143

2153 2161 2179 2203 2207 2213 2221 2237 2239 2243 2251 2267

2269 2273 2281 2287 2293 2297 2309 2311 2333 2339 2341 2347

2351 2357 2371 2377 2381 2383 2389 2393 2399 2411 2417 2423

2437 2441 2447 2459 2467 2473 2477 2503 2521 2531 2539 2543

2549 2551 2557 2579 2591 2593 2609 2617 2621 2633 2647 2657

2659 2663 2671 2677 2683 2687 2689 2693 2699 2707 2711 2713

2719 2729 2731 2741 2749 2753 2767 2777 2789 2791 2797 2801

2803 2819 2833 2837 2843 2851 2857 2861 2879 2887 2897 2903

2909 2917 2927 2939 2953 2957 2963 2969 2971 2999 3001 3011

3019 3023 3037 3041 3049 3061 3067 3079 3083 3089 3109 3119

3121 3137 3163 3167 3169 3181 3187 3191 3203 3209 3217 3221

3229 3251 3253 3257 3259 3271 3299 3301 3307 3313 3319 3323

3329 3331 3343 3347 3359 3361 3371 3373 3389 3391 3407 3413

3433 3449 3457 3461 3463 3467 3469 3491 3499 3511 3517 3527

3529 3533 3539 3541 3547 3557 3559 3571 3581 3583 3593 3607

3613 3617 3623 3631 3637 3643 3659 3671 3673 3677 3691 3697

3701 3709 3719 3727 3733 3739 3761 3767 3769 3779 3793 3797

3803 3821 3823 3833 3847 3851 3853 3863 3877 3881 3889 3907

3911 3917 3919 3923 3929 3931 3943 3947 3967 3989 4001 4003

4007 4013 4019 4021 4027 4049 4051 4057 4073 4079 4091 4093

4099 4111 4127 4129 4133 4139 4153 4157 4159 4177 4201 4211

4217 4219 4229 4231 4241 4243 4253 4259 4261 4271 4273 4283

4289 4297 4327 4337 4339 4349 4357 4363 4373 4391 4397 4409

4421 4423 4441 4447 4451 4457 4463 4481 4483 4493 4507 4513

4517 4519 4523 4547 4549 4561 4567 4583 4591 4597 4603 4621

4637 4639 4643 4649 4651 4657 4663 4673 4679 4691 4703 4721

4723 4729 4733 4751 4759 4783 4787 4789 4793 4799 4801 4813

4817 4831 4861 4871 4877 4889 4903 4909 4919 4931 4933 4937

4943 4951 4957 4967 4969 4973 4987 4993 4999

% of primes = 13

 

Maximum n to compute (0 to quit)? 0