rendered paste bodyimport java.io.*;class Wait { public static void oneSec() { try { Thread.currentThread().sleep(1000); } catch (InterruptedException e) { e.printStackTrace(); } } public static void manySec(long s) { try { Thread.currentThread().sleep(s * 1000); } catch (InterruptedException e) { e.printStackTrace(); } }}public class List{ static StudentRecord initial = null; //for the purpose of starting with the first node static String selected; //Currently selected database public static void main(String[] args) throws IOException { String firstname, lastname, phonenum, input, dbchosen; int grade; int level = 0; boolean crimrecord, filecreated, error; boolean loop = true; File newfile; BufferedReader br = new BufferedReader (new InputStreamReader (System.in)); while (loop) { input = ""; error = false; //Options are selectdb or createdb switch (level) { case 0: System.out.println ("Available commands: (or quit)"); System.out.println ("selectdb - Selects an existing database (also prints a list of databases)"); System.out.println ("createdb - Creates a new database"); System.out.println ("deletedb - Deletes a database"); System.out.println ("--------------"); input = br.readLine(); if (input.equals("selectdb")) { if (viewdbList()) { System.out.println("Enter the name of one of the following available databases:"); dbchosen = br.readLine (); try { FileInputStream fstream = new FileInputStream (dbchosen); } catch (Exception e) { error = true; } if (!error) { selected = dbchosen; fileToList(selected); viewStudentRecords(); level++; } else { System.out.println ("Wrong database chosen"); } } else { System.out.println ("No databases exist. Please create one."); } System.out.println ("--------------"); } else if (input.equals("createdb")) { //create the db here System.out.println("Enter new database name:"); selected = "DB_" + br.readLine(); newfile = new File(selected); filecreated = newfile.createNewFile(); if (filecreated) { System.out.println ("Created successfully"); level++; } else { System.out.println ("Failed: File already exists. Try again."); } System.out.println ("--------------"); } else if (input.equals("quit")) { loop = false; } else if (input.equals ("deletedb")) { if (viewdbList()) { System.out.println("Enter the name of one of the following available databases to delete:"); dbchosen = br.readLine (); try { FileInputStream fstream = new FileInputStream (dbchosen); } catch (Exception e) { error = true; } if (!error) { File deletedb = new File(dbchosen); boolean deletion = deletedb.delete(); if (deletion) { System.out.println ("Deletion success."); } else { System.out.println ("Deletion failed."); } } } else { System.out.println ("No databases to delete"); } } else { System.out.println("Erroneous input"); System.out.println ("--------------"); } break; case 1: System.out.println ("Enter command or type help for a list of available commands"); System.out.println ("--------------"); input = br.readLine(); if (input.equals("enrollStudent")) { System.out.println ("Enter first name"); firstname = br.readLine(); System.out.println ("Enter last name"); lastname = br.readLine(); System.out.println ("Enter grade"); grade = Integer.parseInt(br.readLine()); System.out.println ("Enter phone number"); phonenum = br.readLine(); System.out.println ("Enter criminal record (true/false)"); if ((br.readLine()).equals("true")) { crimrecord = true; } else { crimrecord = false; } enrollStudent(firstname, lastname, grade, phonenum, crimrecord); listToFile(selected); System.out.println ("--------------"); } else if (input.equals("expellStudent")) { System.out.println ("Enter first name"); firstname = br.readLine(); System.out.println ("Enter last name"); lastname = br.readLine(); expellStudent(firstname, lastname); listToFile(selected); System.out.println ("--------------"); } else if (input.equals("enterGrade")) { System.out.println ("Enter first name"); firstname = br.readLine(); System.out.println ("Enter last name"); lastname = br.readLine(); System.out.println ("Enter grade"); grade = Integer.parseInt(br.readLine()); enterGrade(firstname, lastname, grade); listToFile(selected); System.out.println ("--------------"); } else if (input.equals("classAverage")) { System.out.println ("Class average is: " + classAverage()); System.out.println ("--------------"); } else if (input.equals("sortByName")) { sortByName(); viewStudentRecords(); System.out.println ("--------------"); } else if (input.equals("sortByGrade")) { sortByGrade(); viewStudentRecords(); sortByName(); System.out.println ("--------------"); } else if (input.equals("viewdb")) { viewStudentRecords(); System.out.println ("--------------"); } else if (input.equals("back")) { level = 0; initial = null; System.out.println ("--------------"); } else if (input.equals("quit")) { loop = false; } else if (input.equals("help")) { System.out.println ("Available commands: (case-sensitive)"); System.out.println ("enrollStudent - Enrolls a new student"); System.out.println ("expellStudent - Expells a student"); System.out.println ("enterGrade - Enters a new grade for a student"); System.out.println ("classAverage - Prints the class grade average"); System.out.println ("sortByName - Sorts the database by name"); System.out.println ("sortByGrade - Sorts the database by grade"); System.out.println ("viewdb - views the database"); System.out.println ("back - Goes back to previous selection screen"); System.out.println ("--------------"); } else { System.out.println("Erroneous input"); System.out.println ("--------------"); } } } } public static void viewStudentRecords() { StudentRecord currentpos = initial; System.out.println("Last name First name Grade Phone Number Criminal Record"); while (currentpos != null) { System.out.println (currentpos.returnFormattedString ()); currentpos = currentpos.nextStudentRecord (); } } public static void sortByGrade () { StudentRecord currentpos; StudentRecord templink; StudentRecord secondpos; StudentRecord lastpos; StudentRecord previouslink; StudentRecord currentpostemp; boolean sort = true; boolean breakit; int debugcount = 0; //Sort it now (alter the link list) while (sort) { sort = false; //Sorting the first one if (initial.returnGrade() < initial.nextStudentRecord().returnGrade()) { templink = initial.nextStudentRecord(); initial.nextLink(templink.nextStudentRecord()); templink.nextLink(initial); initial = templink; } previouslink = initial; currentpos = initial.nextStudentRecord(); breakit = false; while (!breakit) { currentpostemp = currentpos; secondpos = currentpos.nextStudentRecord(); if (secondpos != null) { if (secondpos.nextStudentRecord() != null) { lastpos = secondpos.nextStudentRecord(); } else { lastpos = null; breakit = true; } } else { break; //Have to do this to catch NULL POINTER EXCEPTION } if (currentpos.returnGrade() < secondpos.returnGrade()) { previouslink.nextLink(secondpos); secondpos.nextLink(currentpos); currentpos.nextLink(lastpos); sort = true; previouslink = currentpostemp; currentpos = currentpostemp.nextStudentRecord(); } else { previouslink = currentpos; currentpos = currentpostemp.nextStudentRecord(); } } } } public static void sortByName () { StudentRecord currentpos; StudentRecord templink; StudentRecord secondpos; StudentRecord lastpos; StudentRecord previouslink; StudentRecord currentpostemp; boolean sort = true; boolean breakit; int debugcount = 0; //Sort it now (alter the link list) while (sort) { sort = false; //Sorting the first one if ((initial.returnlName()).compareTo (initial.nextStudentRecord().returnlName ()) > 0) { templink = initial.nextStudentRecord(); initial.nextLink(templink.nextStudentRecord()); templink.nextLink(initial); initial = templink; } previouslink = initial; currentpos = initial.nextStudentRecord(); breakit = false; while (!breakit) { currentpostemp = currentpos; secondpos = currentpos.nextStudentRecord(); if (secondpos != null) { if (secondpos.nextStudentRecord() != null) { lastpos = secondpos.nextStudentRecord(); } else { lastpos = null; breakit = true; } } else { break; //Have to do this to catch NULL POINTER EXCEPTION } if (currentpos.returnlName().compareTo(secondpos.returnlName()) > 0) { previouslink.nextLink(secondpos); secondpos.nextLink(currentpos); currentpos.nextLink(lastpos); sort = true; previouslink = currentpostemp; currentpos = currentpostemp.nextStudentRecord(); } else { previouslink = currentpos; currentpos = currentpostemp.nextStudentRecord(); } } } } public static void enrollStudent(String firstname, String lastname, int grade, String phonenumber, boolean criminalrecord) { StudentRecord newStudentRecord = new StudentRecord(firstname, lastname, grade, phonenumber, criminalrecord); if (initial != null) { if (lastname.compareTo (initial.returnlName ()) < 0) { newStudentRecord.nextLink(initial); initial = newStudentRecord; } else { StudentRecord searchResult = searchByName(firstname, lastname); newStudentRecord.nextLink (searchResult.nextStudentRecord()); searchResult.nextLink (newStudentRecord); } } else { initial = newStudentRecord; newStudentRecord.nextLink(null); } } //Expells the student //The searchByName cannot be used (as there is no link to the previous node) public static void expellStudent(String firstname, String lastname) { if (initial != null) { if (((initial.returnlName()).equals(lastname)) && ((initial.returnfName()).equals(firstname))) { //First check if the first user in the list is a match initial = initial.nextStudentRecord(); } else { StudentRecord currentpos = initial; boolean foundpos = false; //Checks for two records ahead so that it's possible to expel the last student in the list //without having a null pointer exception while ((currentpos.nextStudentRecord()).nextStudentRecord() != null && !foundpos) { if (lastname.compareTo ((currentpos.nextStudentRecord ()).returnlName ()) > 0) { currentpos = currentpos.nextStudentRecord(); } else { foundpos = true; } } currentpos.nextLink(currentpos.nextStudentRecord().nextStudentRecord()); } } else { System.out.println ("No students to expell"); } } public static int classAverage() { StudentRecord currentpos = initial; int gradeTotal = 0; int numStudents = 0; while (currentpos.nextStudentRecord() != null) { gradeTotal = gradeTotal + currentpos.returnGrade(); numStudents++; currentpos = currentpos.nextStudentRecord(); } return gradeTotal / numStudents; } //Enters a new grade for a student (no output) public static void enterGrade(String firstname, String lastname, int newgrade) { if (initial != null) { if (((initial.returnlName()).equals(lastname)) && ((initial.returnfName()).equals(firstname))) { initial.assignGrade(newgrade); } else { StudentRecord searchResult = searchByName(firstname, lastname); searchResult.nextStudentRecord().assignGrade(newgrade); } } else { System.out.println ("Error: No entries exist in database"); } } //Performs a search for the name (outputs the search result) private static StudentRecord searchByName(String firstname, String lastname) { boolean foundpos = false; StudentRecord current = initial; if (lastname.compareTo (current.returnlName ()) < 0) { foundpos = true; } while (((current.nextStudentRecord ()) != null) && !foundpos) //Start the search { if (lastname.compareTo ((current.nextStudentRecord ()).returnlName ()) > 0) //Compare the entry and the existing { current = current.nextStudentRecord (); //Advance to the next one } else { foundpos = true; //or indicate the position is found } } return current; } public static boolean viewdbList () throws IOException{ //Lists the List .txt files in the List folder and their respective ids //List files start with "DB" and have no extention String userdir = System.getProperty ("user.dir"); boolean condition = false; File f = new File (userdir); String[] files = f.list (); for (int i = 0 ; i < files.length ; i++) { File f2 = new File (userdir, files [i]); if (!f2.isDirectory () && f2.exists ()) { if (f2.isFile ()) { //Check if it starts with "DB" if ((f2.getName ().charAt (0) == 68) && (f2.getName ().charAt (1) == 66)) { System.out.println (f2.getName ()); condition = true; } } } } return condition; } public static void fileToList(String dbname) { try { FileInputStream fstream = new FileInputStream(dbname); DataInputStream lines = new DataInputStream(fstream); while (lines.available() !=0) { //Now seperate lines String[] parsed = parseLine(lines.readLine()); boolean crimrecord = false; if (parsed[4].equals("true")) { crimrecord = true; } enrollStudent(parsed[0], parsed[1], Integer.parseInt(parsed[2]), parsed[3], crimrecord); } lines.close(); } catch (Exception e) { System.err.println("File error"); } } public static void listToFile(String dbname) { try { FileOutputStream database = new FileOutputStream(selected); PrintStream p = new PrintStream(database); StudentRecord currentpos = initial; while (currentpos != null) { p.println ("^" + currentpos.returnfName() + "^" + currentpos.returnlName() + "^" + currentpos.returnGrade() + "^" + currentpos.returnPhoneNum() + "^" + currentpos.returnCrimRecord() + "^"); currentpos = currentpos.nextStudentRecord (); } p.close(); } catch (Exception e) { System.out.println ("Error writing to file"); } } private static String[] parseLine(String line) { String curstring = ""; int inputcount = 0; String[] rarray = new String[5]; for (int i = 0; i < line.length(); i++) { //System.out.println("Current character: " + i); if (line.charAt(i) == 94) { //To prevent the addition of a ^ to the first return if (i == 0) { i++; } //System.out.println("Character is a ^"); if (curstring.equals("")) { //System.out.println("Curstring = " + curstring); curstring = String.valueOf(line.charAt(i)); //System.out.println("Now Curstring = " + curstring); } else { //System.out.println("Curstring to return = " + curstring); rarray[inputcount] = curstring; inputcount++; curstring = ""; } } else { curstring = curstring + String.valueOf(line.charAt(i)); } } return rarray; } }class StudentRecord{ String fName, lName, phoneNum; int grade; boolean crimRecord; StudentRecord next; public StudentRecord (String fname1, String lName1, int grade1, String phoneNum1, boolean crimRecord1) { fName = fname1; lName = lName1; grade = grade1; phoneNum = phoneNum1; crimRecord = crimRecord1; } public StudentRecord nextStudentRecord() { return next; } public String returnlName() { return lName; } public String returnfName() { return fName; } public void nextLink (StudentRecord newLink) { next = newLink; } public int returnGrade () { return grade; } public String returnPhoneNum() { return phoneNum; } public boolean returnCrimRecord() { return crimRecord; } public void assignGrade (int newGrade) { grade = newGrade; } public String returnFormattedString () { return (lName + generateSpaces(18 - lName.length()) + fName + generateSpaces(18 - fName.length()) + grade + generateSpaces(6 - String.valueOf(grade).length()) + phoneNum + generateSpaces(15 - phoneNum.length()) + crimRecord); } private String generateSpaces(int numspaces) { String spaces = ""; for (int i = 0; i < numspaces; i++) { spaces = spaces + " "; } return spaces; }}