Question

This is an optional assignment and is worth a maximum of 100 points. Load an array of 100 student numbers from the included file Students.txt. (It is located with the other class files) Prompt the user to search for a student

Answer 1

import java.io.FileReader;
import java.io.IOException;
import java.util.Scanner;

public class StudentGroup 
{
        // Maximum number of students stored in array
        private final static int MAX_STUDENTS = 200;
        
        // Instance variables
        private Student[] students;     // array of Student objects
        private int numStudents;        // number of actual objects in array

        /** Constructs an empty student group with capacity for MAX_STUDENTS
         */
        public StudentGroup() 
        {
                students = new Student[MAX_STUDENTS];
                numStudents = 0;
        }
        
        /** Constructs a student group with capacity for MAX_STUDENTS
         *  and populates it with the student data found in the given file
         *  @param fileName name of file containing student data
         */
        public StudentGroup(String fileName) 
        {
                students = new Student[MAX_STUDENTS];
                numStudents = 0;
                readFile(fileName);
        }

        /** Searches the students[] via a linear search to find a student object based on its name
         *  @param name the name of the student that is being searched for
         *      @return the student object with the matching name
         */

        public Student findByName(String name) 
        {
                Student stu = null;
                for (int x = 0; x < numStudents; x++)
                {
                        if (students[x].getName().equals(name))
                        {
                                stu = students[x];
                        }

                }
                return stu;
                
        }

        /** 
         * Sorts the students[] by insertion sort
         */
        
        public void sortByName() 
        {
                for (int x = 1; x < numStudents; x++)
                {
                        Student key = students[x]; //defines the key to compare agaisnt
                        int location = x;
                        while (location > 0 && key.getName().compareTo(students[location - 1].getName()) < 0)
                        {
                                students[location] = students[location - 1]; //swaps location
                                location--;
                        }
                        students[location] = key; //defines new key
                }
        }

        /**
         * Sorts the students[] by a selection sort
         */

        public void sortByID() 
        {
                for (int x = 0; x < numStudents - 1; x++)
                {
                        int minIndex = x; //sets the minimum index
                        for (int y = x + 1; y < numStudents; y++)
                        {
                                if (students[y].getID() < students[minIndex].getID())
                                {
                                        minIndex = y; //if the student's ID at index y is less than the student's ID at the minimum index, let y be the new minIndex
                                }
                        }
                        Student temp = students[x];      
                        students[x] = students[minIndex]; //swaps the students
                        students[minIndex] = temp;
                }
        }

        /** Searches the students[] by using a binary search and finds a student based on matching ID number. Search returns the student if found, otherwise it returns null.
         * @param id the id number to be seached for
         * @return student object with matching ID number
         */

        public Student findByID(int id) 
        {
                int low = 0;
                int high = numStudents - 1;
                while (low <= high)
                {
                        int middle = (low + high) / 2;
                        if (students[middle].getID() == id)
                        {
                                return students[middle];
                        }
                        else if(id < students[middle].getID())
                        {
                                high = middle - 1;
                        }
                        else
                        {
                                low = middle + 1;
                        }
                }
                return null;
        }

        /** Provides the group of students
         *  @return the group of students as a string
         */
        public String toString() 
        {
                String str = "[";
                for (int k = 0; k < numStudents; k++) 
                {
                        str += students[k].toString();
                        if (k == numStudents-1) 
                                str += "]";
                        else
                                str += ",\n ";
                }
                return str;
        }

        /** Reads student entries from a given file and stores them in the array
         *  @param fileName name of file containing student data in format
         *         LAST<space>FIRST<space>ID<space>GPA
         */
        private void readFile(String fileName) 
        {
                try 
                {
                        // Open file for reading
                        Scanner scan = new Scanner(new FileReader(fileName));
                        
                        // Continue reading and adding students until there are no more entries
                        // Entries are in form LAST<space>FIRST<space>ID<space>GPA
                        while (scan.hasNextLine()) 
                        {                                               
                                String inputStr = scan.nextLine();
                                Scanner strScan = new Scanner(inputStr);
                                String lastName = strScan.next();
                                String firstName = strScan.next();
                                int id = strScan.nextInt();
                                double gpa = strScan.nextDouble();

                                Student stu = new Student(lastName, firstName, id, gpa);
                                students[numStudents] = stu;
                                numStudents++;
                        }
                        scan.close();
                } 
                catch (IOException e) 
                {
                        System.out.println("Error reading from file " + fileName +
                                                                          "\nError:  " + e.getMessage());
                } 
                catch (Exception e) 
                {
                        System.out.println("Error reading from file " + fileName +
                                                                          "\nError:  " + e.getMessage());
                }
        }
}

Studentgroup.java

import java.io.FileReader;
import java.io.IOException;
import java.util.Scanner;

public class StudentGroup
{
// Maximum number of students stored in array
private final static int MAX_STUDENTS = 200;

// Instance variables
private Student[] students; // array of Student objects
private int numStudents; // number of actual objects in array

/** Constructs an empty student group with capacity for MAX_STUDENTS
*/
public StudentGroup()
{
students = new Student[MAX_STUDENTS];
numStudents = 0;
}

/** Constructs a student group with capacity for MAX_STUDENTS
* and populates it with the student data found in the given file
* @param fileName name of file containing student data
*/
public StudentGroup(String fileName)
{
students = new Student[MAX_STUDENTS];
numStudents = 0;
readFile(fileName);
}

/** Searches the students[] via a linear search to find a student object based on its name
* @param name the name of the student that is being searched for
* @return the student object with the matching name
*/

public Student findByName(String name)
{
Student stu = null;
for (int x = 0; x < numStudents; x++)
{
if (students[x].getName().equals(name))
{
stu = students[x];
}

}
return stu;

}

/**
* Sorts the students[] by insertion sort
*/

public void sortByName()
{
for (int x = 1; x < numStudents; x++)
{
Student key = students[x]; //defines the key to compare agaisnt
int location = x;
while (location > 0 && key.getName().compareTo(students[location - 1].getName()) < 0)
{
students[location] = students[location - 1]; //swaps location
location--;
}
students[location] = key; //defines new key
}
}

/**
* Sorts the students[] by a selection sort
*/

public void sortByID()
{
for (int x = 0; x < numStudents - 1; x++)
{
int minIndex = x; //sets the minimum index
for (int y = x + 1; y < numStudents; y++)
{
if (students[y].getID() < students[minIndex].getID())
{
minIndex = y; //if the student's ID at index y is less than the student's ID at the minimum index, let y be the new minIndex
}
}
Student temp = students[x];     
students[x] = students[minIndex]; //swaps the students
students[minIndex] = temp;
}
}

/** Searches the students[] by using a binary search and finds a student based on matching ID number. Search returns the student if found, otherwise it returns null.
* @param id the id number to be seached for
* @return student object with matching ID number
*/

public Student findByID(int id)
{
int low = 0;
int high = numStudents - 1;
while (low <= high)
{
int middle = (low + high) / 2;
if (students[middle].getID() == id)
{
return students[middle];
}
else if(id < students[middle].getID())
{
high = middle - 1;
}
else
{
low = middle + 1;
}
}
return null;
}

/** Provides the group of students
* @return the group of students as a string
*/
public String toString()
{
String str = "[";
for (int k = 0; k < numStudents; k++)
{
str += students[k].toString();
if (k == numStudents-1)
str += "]";
else
str += ",\n ";
}
return str;
}

/** Reads student entries from a given file and stores them in the array
* @param fileName name of file containing student data in format
*         LAST<space>FIRST<space>ID<space>GPA
*/
private void readFile(String fileName)
{
try
{
// Open file for reading
Scanner scan = new Scanner(new FileReader(fileName));

// Continue reading and adding students until there are no more entries
// Entries are in form LAST<space>FIRST<space>ID<space>GPA
while (scan.hasNextLine())
{
String inputStr = scan.nextLine();
Scanner strScan = new Scanner(inputStr);
String lastName = strScan.next();
String firstName = strScan.next();
int id = strScan.nextInt();
double gpa = strScan.nextDouble();

Student stu = new Student(lastName, firstName, id, gpa);
students[numStudents] = stu;
numStudents++;
}
scan.close();
}
catch (IOException e)
{
System.out.println("Error reading from file " + fileName +
"\nError: " + e.getMessage());
}
catch (Exception e)
{
System.out.println("Error reading from file " + fileName +
"\nError: " + e.getMessage());
}
}
}

/**
 * StudentGroupTest.java
 * Test the StudentGroup class
 */

public class StudentGroupTest 
{
        public static void main(String[] args) 
        {
                StudentGroup apcs1 = new StudentGroup("apcs1.txt");
                System.out.println("Students\n" + apcs1 + "\n");

                
                // Test findByName, a linear search
                System.out.println("Searching by name:");
                Student small = apcs1.findByName("Fry, Small");
                if (small == null)
                        System.out.println("Unable to find Fry, Small");
                else
                        System.out.println("Found:  " + small.toString());

                Student big = apcs1.findByName("Dude, Big");
                if (big == null)
                        System.out.println("Unable to find Dude, Big");
                else
                        System.out.println("Found:  " + big.toString());
                System.out.println();


                
                // Test sortByName, an Insertion Sort
                apcs1.sortByName();
                System.out.println("Students sorted by name\n" + 
                                                                        apcs1 + "\n");
        
                

        
                // Test sortByID, a Selection Sort
                apcs1.sortByID();
                System.out.println("Students sorted by ID\n" + 
                                                                        apcs1 + "\n");


                
                // Test findByID, a binary search
                System.out.println("Searching by ID:");
                Student stu5927 = apcs1.findByID(5927);
                if (stu5927 == null)
                        System.out.println("Unable to find student with ID 5927");
                else
                        System.out.println("Found:  " + stu5927.toString());

                Student stu1111 = apcs1.findByID(1111);
                if (stu1111 == null)
                        System.out.println("Unable to find student with ID 1111");
                else
                        System.out.println("Found:  " + stu1111.toString());
                System.out.println();
        
        }
}

apcs1.txt

Wolf Mighty 2933 4.521
Smart Geraldine 1234 3.5
Fry Small 1524 3.9
Curve Belo 9342 2.5
Passing Ima 3927 2.75
Failing Huzza 5927 1.85
Average Justine 6322 3.2
Pants Smarty 1523 4.239
Enovera Marge 3926 3.999