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README.md

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 # JavaDataStructures
-A repository for the Java programming projects I did in my Data Structures class.
+A repository for the Java programming projects I did in my Data Structures class. {{Under contruction}} I need to delete all unneccesary test files/ clean up some of my code.
+

lab1/ArrayList1.java

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+// file name -- ArrayList1.java
+import java.io.*;
+import java.util.*;
+
+/**
+   This program shows how to read in student records from an input
+   data fle and store them in an array list. Student records are
+   stored using an ArrayList object.
+*/
+public class ArrayList1
+{
+   private ArrayList<Student> students;
+   private Scanner infile;
+
+   public static void main(String[] args)
+      throws IOException
+   {
+      ArrayList1 current;
+
+      current = new ArrayList1();
+      current.getStarted();
+   } // method main
+
+   private double gpa;
+   private double sumGPA;
+   private double averageGPA;
+   /**
+      Starts the program
+   */
+   public void getStarted()
+      throws FileNotFoundException
+   {
+      openFile();
+      readData();
+      displayResults();
+      System.out.println("Average GPA:" + averageGPA);
+      infile.close();
+   } // method getStarted
+
+
+   /**
+      Opens the input data file for read access.
+   */
+   public void openFile() throws FileNotFoundException
+   {
+      Scanner input;
+      String infile_name;
+      File file;
+
+      input = new Scanner(System.in);
+      do
+      {
+         System.out.print("Enter the input file name: ");
+         infile_name = input.next();
+
+         // open the input data file
+         file = new File(infile_name);
+         if (file.exists())
+            infile = new Scanner(new File(infile_name));
+         else
+            System.out.println(infile_name + " does not exist");
+      } while (!file.exists());
+   } // method openFile
+
+
+   /**
+      Reads in text from file and save them in an array list.
+      @param infile the file which has been open successfully
+   */
+   public void readData()
+   {
+      Student who;
+      String name, first_name, last_name;
+      int age;
+
+      int count;
+
+      count = 0;
+      sumGPA = 0;
+
+      // instantiate an ArrayList object
+      students = new ArrayList<Student>();
+
+      // read in values from the file and assign them to the elements
+      while (infile.hasNext())
+      {
+         first_name = infile.next();
+         last_name = infile.next();
+         name = first_name + " " + last_name;
+         age = infile.nextInt();
+         gpa = infile.nextDouble();
+
+         count++;
+         sumGPA = sumGPA + gpa;
+
+
+         who = new Student(name, age, gpa);
+         students.add(who);
+      }
+      averageGPA = sumGPA / count;
+
+   } // method readData
+
+
+   /**
+      Displays the student records stored in the array list.
+   */
+   public void displayResults()
+   {
+      // display the array elements in sequence
+      System.out.println("The list contains " + students.size() +
+                         " students");
+      for (Student who: students)
+         displayStudentRecord(who);
+   } // method displayResults
+
+
+   /**
+      Displays the content of each student record.
+      @param who a reference to a Student object for display
+   */
+   public void displayStudentRecord(Student who)
+   {
+
+      System.out.println("Name: " + who.getName());
+      System.out.println("Age: " + who.getAge());
+      System.out.println("GPA: " + who.getGPA());
+
+   } // method displayStudentRecord
+} // class ArrayList1

lab1/Student.java

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+// file name -- Student.class
+
+/**
+   A class to represent students objects.
+   Many of the functions are easy to see representations of getters and setters.
+*/
+public class Student
+{
+   private String name;
+   private int age;
+   private double gpa;
+
+   /**
+      Initializes the members of a Student object.
+      @param name a string representing the name of the student
+      @param age an integer representing the age of the student
+      @param gpa a double value representing the gpa of the student
+   */
+   public Student(String name,
+                  int age,
+                  double gpa)
+   {
+      this.name = name;
+      this.age = age;
+      this.gpa = gpa;
+   } // constructor
+
+
+   /**
+      Assigns a new name.
+      @param name a string representing the student's name
+   */
+   public void setName(String name)
+   {
+      this.name = name;
+   } // method setName
+
+
+   /**
+      Assigns a new age.
+      @param age an integer representing the student's age
+   */
+   public void setAge(int age)
+   {
+      this.age = age;
+   } // method setAge
+
+
+   /**
+      Assigns a new gpa.
+      @param age a double value representing the student's gpa
+   */
+   public void setGPA(double gpa)
+   {
+      this.gpa = gpa;
+   } // method setGPA
+
+
+   /**
+      Returns the name of the student.
+      @return student's name
+   */
+   public String getName()
+   {
+      return name;
+   } // method getName
+
+
+   /**
+      Returns the age of the student.
+      @return student's age
+   */
+   public int getAge()
+   {
+      return age;
+   } // method getAge
+
+
+   /**
+      Returns the gpa of the student.
+      @return student's gpa
+   */
+   public double getGPA()
+   {
+      return gpa;
+   } // method getGPA
+
+} // class Student

lab1/student.dat

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+James Bond 48 3.25
+Jim Smith 20 3.75
+Jean Wilson 19 3.52
+John Doe 22 2.5
+Willie Fields 25 2.95

lab2/FormattedInput02.java

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+/**
+  file name -- FormattedInput02.java
+  This program shows how to read formatted data from a text file.
+
+  The data file contains student records which are formatted as follows:
+
+          Field name            Columns (a.k.a. indexes)
+     ==========================================
+             Name                1 - 20
+             Age                21 - 22
+             gpa                23 - 27
+             ssNumber           28 - 36
+     ==========================================
+*/
+
+
+import java.io.*;
+import java.util.*;        // for Scanner class
+
+
+class FormattedInput02
+{
+  //final keyword makes these varibales, constant values, meaning you can't change them when aprogram is running.
+  //private keyword makes it so that these variables can only be accesed inside of the class.
+   private static final int NAME_WIDTH = 20;
+   private static final int AGE_WIDTH = 2;
+   private static final int GPA_WIDTH = 5;
+   private static final int SSNUMBER_WIDTH = 9;
+
+   private Scanner infile;
+   private ArrayList<Student> list;
+
+   public static void main(String list[]) throws IOException
+   {
+      FormattedInput02 one;
+
+     //makes a new instance of this class
+      one = new FormattedInput02();
+
+      one.getStarted();
+   } // method main
+
+
+   /**
+      Default Constructor
+      This makes creates a new Student type array list.
+   */
+   public FormattedInput02()
+   {
+      list = new ArrayList<Student>();
+   } // constructor
+
+
+   /**
+      Starts the program using an object of the class
+   */
+   public void getStarted() throws FileNotFoundException
+   {
+      openFile();
+      readData();
+      display();
+   } // method getStarted
+
+
+   /**
+      Opens the input data file for read access.
+  */
+   public void openFile() throws FileNotFoundException
+   {
+      Scanner input;
+      String infile_name;
+      File file;
+
+     //Scanner will look for keyboard input.
+      input = new Scanner(System.in);
+
+      do
+      {
+         System.out.print("Enter the input file name: ");
+        //gets files name. stops looking at keybaord when user presses ENTER
+         infile_name = input.next();
+
+         file = new File(infile_name);
+         if (file.exists())
+            infile = new Scanner(file);
+         else
+            System.out.println(infile_name + " does not exist");
+       } while (!file.exists());
+   } // method openFile
+
+
+   /**
+      Reads student records from the file and separate the fields of
+      each record using substring method.
+   */
+   public void readData()
+   {
+      String name, text;
+      int age;
+      double gpa;
+      String ssNumber;
+      Student who;
+
+      while (infile.hasNextLine())
+      {
+         text = infile.nextLine();
+
+         // obtain name field
+         name = text.substring(0, NAME_WIDTH); // extract name field
+         name = name.trim(); // remove leading and trailing spaces
+        //definetly need to use trim here, as we captured the name and all of the space behind them name and placed
+        //that into the name variable.
+
+         // remove the whole name field from text. Now substring index can start at 0 again for other variables.
+         text = text.substring(NAME_WIDTH, text.length());
+
+         // extract age field from text and convert it to an int type
+         age = Integer.parseInt(text.substring(0, AGE_WIDTH));
+
+         // extract gpa field from text and convert it to a double type. We place AGE_WIDTH into the first parameter
+        //as gpa is after it.
+         gpa = Double.parseDouble(text.substring(AGE_WIDTH, AGE_WIDTH+GPA_WIDTH)); //AGE_WIDTH + GPA_WIDTH
+
+         ssNumber = text.substring(AGE_WIDTH+GPA_WIDTH,AGE_WIDTH+GPA_WIDTH+SSNUMBER_WIDTH);
+
+
+         who = new Student(name, age, gpa, ssNumber);
+         //socialSecurity
+
+         list.add(who);
+      } // while infile still has data
+   } // method readData
+
+
+   public void display()
+   {
+      for (Student who : list)
+      {
+         System.out.println("Name: " + who.getName());
+         System.out.println("Age: " + who.getAge());
+         System.out.println("GPA: " + who.getGPA());
+         System.out.println("Social Security:" + who.getssNumber());
+      } // for still student records available
+   } // method display
+
+} // class FormattedInput02