### Learning Objectives

• Use the Integer wrapper class.
• Declare and use ArrayList class objects.
• Write code to read from, and write to, text files.
• Write an exception handler for an I/O exception.
• Write Java classes and instantiate objects of those classes.

### 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 list i , list i+1 , list i+2 , ..., list i+k , that is monotonically increasing (i.e., list i+j list i+j-1 for each j = 1, 2, 3, ..., k). Similarly, a run down is a (k+1)-length subsequence list i , list i+1 , list i+2 , ..., list i+k , that is monotonically decreasing (i.e., list i+j-1 list i+j for each j = 1, 2, 3, ..., k). For the above example list we have these runs up and runs down:

Runs Up
list 0 through list 1 = { 2, 8 }; k = 1
list 2 = { 3 }; k = 0
list 3 through list 4 = { 2, 9 }; k = 1
list 5 = { 8 }; k = 0
list 6 = { 6 }; k = 0
list 7 through list 9 = { 3, 4, 6 }; k = 2
list 10 through list 11 = { 1, 9 }; k = 1
Runs Down
list 0 = { 2 }; k = 0
list 1 through list 3 = { 8, 3, 2 }; k = 2
list 4 through list 7 = { 9, 8, 6, 3 }; k = 3
list 8 = { 4 }; k = 0
list 9 through list 10 = { 6, 1 }; k = 1
list 11 = { 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 runs k , 0 < k < n - 1. For the example list we have:

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

### Software Requirements

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
8
6
3 4 6 1 9

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

3. The program shall compute runs total .

4. The program shall produce an output file named p01-runs.txt containing runs total and runs k 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.

### Software Design

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.

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< Integer> 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. F

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

### Pseudocode

Method Run() Returns Nothing
Declare and create an ArrayList of Integers named list
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