2 Learning Objectives

1. Use the Integer wrapper class.

2. Declare and use ArrayList class objects.

3. Write code to read from, and write to, text files.

4. Write an exception handler for an I/O exception.

5. Write Java classes and instantiate objects of those classes.

3 Background

Let list be a nonempty sequence of nonnegative random integers, each in the range [0, 32767] and let n be the length of

list, e.g.,

list = { 2, 8, 3, 2, 9, 8, 6, 3, 4, 6, 1, 9 }

where n = 12. List elements are numbered starting at 0. We define a run up to be a (k+1)-length subsequence listi, listi+1,

listi+2, ..., listi+k, that is monotonically increasing (i.e., listi+j listi+j-1 for each j = 1, 2, 3, ..., k). Similarly, a run down

is a (k+1)-length subsequence listi, listi+1, listi+2, ..., listi+k, that is monotonically decreasing (i.e., listi+j-1 listi+j for each

j = 1, 2, 3, ..., k). For the above example list we have these runs up and runs down:

Runs Up

list0 through list1 = { 2, 8 }; k = 1

list2 = { 3 }; k = 0

list3 through list4 = { 2, 9 }; k = 1

list5 = { 8 }; k = 0

list6 = { 6 }; k = 0

list7 through list9 = { 3, 4, 6 }; k = 2

list10 through list11 = { 1, 9 }; k = 1

Runs Down

list0 = { 2 }; k = 0

list1 through list3 = { 8, 3, 2 }; k = 2

list4 through list7 = { 9, 8, 6, 3 }; k = 3

list8 = { 4 }; k = 0

list9 through list10 = { 6, 1 }; k = 1

list11 = { 9 }; k = 0

We are interested in the value of k for each run up and run down and in particular we are interested in the total umber of

runs for each nonzero k, which we shall denote by runsk, 0 < k < n - 1. For the example list we have:

k runsk runs

1 4 { 2, 8 }, { 2, 9 }, { 1, 9 }, and { 6, 1 }

2 2 { 3, 4, 6, } and { 8, 3, 2 }

3 1 { 9, 8, 6, 3 }

4-11 0

Let runstotal be the the sum from k = 1 to n - 1 of runsk. For the example list, runstotal = 4 + 2 + 1 = 7.

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link

in the course schedule

CSE205 Object Oriented Programming and Data Structures Programming Project 1 :: 25 pts

4 Software Requirements

Your program shall:

1. Open a file named p01-in.txt containing n integers, 1 n 1000, with each integer in [0, 32767]. There will be one

or more integers per line. A sample input file:

Sample p01-in.txt

2 8 3

2 9

863

4 6 1 9

2. The program shall compute runsk for k = 1, 2, 3, ..., n - 1.

3. The program shall compute runstotal.

4. The program shall produce an output file named p01-runs.txt containing runstotal and runsk for k = 1, 2, 3, ..., n - 1.

The file shall be formatted as shown in the example file below.

Sample p01-runs.txt

runs_total, 7

runs_1, 4

runs_2, 2

runs_3, 1

runs_4, 0

runs_5, 0

runs_6, 0

5. If the input file p01-in.txt cannot be opened for reading (because it does not exist) then display an error message on

the output window and immediately terminate the program, e.g.,

run program...

Sorry, could not open 'p01-in.txt' for reading. Stopping.

5 Software Design

Your program shall:

1. Contain a class named Main. This class shall contain the main() method. The main() method shall instantiate an

object of the Main class and call run() on that object.

// Main.java

public class Main {

public static void main(String[] pArgs) {

Main mainObject = new Main();

mainObject.run()

} private void run() {

// You will start writing code here to implement the software requirements.

}

}

2. One of the primary objectives of this programming project is to learn to use the java.util.ArrayList class. Therefore,

you are not permitted to use 1D arrays. Besides, you will quickly discover that the ArrayList class is more

convenient to use than 1D arrays.

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CSE205 Object Oriented Programming and Data Structures Programming Project 1 :: 25 pts

3. ArrayList is a generic class meaning: (1) that it can store objects of any class; and (2) when an ArrayList object is

declared and instantiated we must specify the class of the objects that will be stored in the ArrayList. For this

project, you need to define an ArrayList that stores integers, but you cannot specify that your ArrayList stores ints

because int is a primitive data type and not a class. Therefore, you will need to use the java.lang.Integer wrapper

class:

ArrayList list = new ArrayList<>():

int x = 1;

list.add(x); // Legal because of Java autoboxing.

4. You must write an exception handler that will catch the FileNotFoundException that gets thrown when the input

file does not exist (make sure to test this). The exception handler will print the friendly error message and

immediately terminate the Java program. To immediately terminate a Java program we call a static method named

exit() which is in the java.lang.System class. The exit() method expects an int argument. For this project, it does not

matter what int argument we send to exit(). Therefore, terminate the program this way:

try {

// Try to open input file for reading

} catch (FileNotFoundException pExcept) {

// Print friendly error message

System.exit(-1);

}

5. Your programming skills should be sufficiently developed that you are beyond writing the entire code for a program

in one method. Divide the program into multiple methods. Remember, a method should have one purpose, i.e., it

should do one thing. If you find a method is becoming complicated because you are trying to make that method do

more than one thing, then divided the method into 2, 3, 4, or more distinct methods, each of which does one thing.

6. Avoid making every variable or object an instance variable. For this project you shall not declare any instance

variables in the class. That is, all variables should be declared as local variables in methods and passed as

arguments to other methods when appropriate.

7. Format your code neatly. Use proper indentation and spacing. Study the examples in the book and the examples the

instructor presents in the lectures and posts on the course website.

8. Put a comment header block at the top of each method formatted thusly:

/**

* A brief description of what the method does.

*/

9. Put a comment header block at the top of each source code filenot just for this project, but for every project we

writeformatted thusly:

//********************************************************************************************************

// CLASS: classname (classname.java)

//

// DESCRIPTION

// A description of the contents of this file.

//

// COURSE AND PROJECT INFO

// CSE205 Object Oriented Programming and Data Structures, semester and year

// Project Number: project-number

//

// AUTHOR

// your-name (your-email-addr)

//********************************************************************************************************

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CSE205 Object Oriented Programming and Data Structures Programming Project 1 :: 25 pts

6 Pseudocode

Method Run() Returns Nothing

Declare and create an ArrayList of Integers named list

list ReadFile("p01-in.txt")

Declare and create an ArrayList of Integers named listRunsUpCount

Declare and create an ArrayList of Integers named listRunsDnCount

listRunsUpCount FindRuns(list, RUNS_UP)

listRunsUpCount FindRuns(list, RUNS_DN)

Declare and create an ArrayList of Integers named listRunsCount

listRunsCount Merge(listRunsUpCount, listRunsDnCount)

Output("p01-runs.txt", listRunsCount)

End Method Run

Method FindRuns(In: pList is ArrayList of Integers; int pDir is RUNS_UP or RUNS_DN) Returns ArrayList of Integers

listRunsCount arrayListCreate(pList.size(), 0)

Declare int varaibles i 0, k 0

While i < pList.size() - 1 Do

If pDir is RUNS_UP and pList element at i is pList element at i + 1 Then

Increment k

ElseIf pDir is RUNS_DN and pList element at i is pList element at i + 1 Then

Increment k

Else

If k 0 Then

Increment the element at index k of listRunsCount

k 0

End if

End If

Increment i

End While

If k 0 Then

Increment the element at index k of listRunsCount

End If

Return listRunsCount

End Method FindRuns

Method Merge(In: pListRunsUpCount, In: pListRunsDnCount) Returns ArrayList of Integers

listRunsCount arrayListCreate(pListRunsUpCount.size(), 0)

For i 0 to pListRunsUpCount.size() - 1 Do

Set element i of listRunsCount to the sum of the elements at i in pListRunsUpCount and pListRunsDnCount

End For

Return listRunsCount

End Method Merge

Method arrayListCreate(In: int pSize; In: int pInitValue) Returns ArrayList of Integers

Declare and create an ArrayList of Integers named list

Write a for loop that iterates pSize times and each time call add(pInitValue) on list

Return list

End Method arrayListCreate

Method Output(In: pFilename; pListRuns ArrayList of Integers) Returns Nothing

out open pFilename for writing

out.print("runs_total, ", the sum of pListRuns)

For k 1 to pListRuns.size() - 1 Do

out.print("runs_k, ", the element at index k of pListRuns)

End For

Close out

End Method Output

p01-in.txt---------------

2 8 3

2 9

8

6

3 4 6 1 9

p01-runs.txt--------

runs_total, 7

runs_1, 4

runs_2, 2

runs_3, 1

runs_4, 0

runs_5, 0

runs_6, 0