I'm having trouble with a project for my Java data structures and algorithms class. I have a classroom program with an option to create, update, display, or see all students.
Can someone help me by implementing a sorting algorithm and explain it? I was trying to sort the students by grade but I don't know how to implement it with a user input.
Here is main:
package main;
import school.School;
public class Main {
public static void main(String[] args) {
School aSchool = new School();
aSchool.initialMenu();
}
}
Here is school:
package school;
import java.io.PrintStream;
import java.util.Scanner;
import student.Student;
public class School {
private final Scanner keyboard = new Scanner(System.in);
private final PrintStream messagePane = new PrintStream(System.out, true);
private int nextAvailablePosition;
private Student[] classroom;
public School() {
super();
}
private void initializeArray() {
classroom = new Student[4];
nextAvailablePosition = 0;
}
private void storeStudentInArray(Student aStudent) {
assert aStudent != null : "Null parameter supplied to School.storeStudentInArray()";
if (nextAvailablePosition >= classroom.length) {
Student[] biggerClassroom = new Student[(int) (classroom.length * 1.5)];
System.arraycopy(classroom, 0, biggerClassroom, 0, classroom.length);
classroom = biggerClassroom;
}
classroom[nextAvailablePosition] = aStudent;
nextAvailablePosition++;
}
private Student searchForStudentInArray(String searchID) {
assert searchID != null : "Null parameter supplied to School.searchForStudentInArray()";
int index = 0;
while (index < nextAvailablePosition) {
if (searchID.equalsIgnoreCase(classroom[index].getID())) {
return classroom[index];
}
index++;
}
return null;
}
public void initialMenu() {
initializeArray();
boolean stillWorking = true;
do {
messagePane.print("\n"
+ "WELCOME to the Student Database Organizer 1.0!\n"
+ "Here you can store students in a virtual classroom.\n"
+ "\n"
+ "(C)reates a Student\n"
+ "(U)pdate a Student\n"
+ "(D)isplay a Student\n"
+ "(A)ll Students\n"
+ "(E)nd\n"
+ "Enter Letter Here: \n");
String initialResponse = keyboard.nextLine();
String response = initialResponse.trim().toUpperCase();
if (response.length() > 0) {
response = response.substring(0, 1);
if (response.equals("E")) {
stillWorking = false;
} else if (response.equals("U")) {
updateStudent();
} else if (response.equals("D")) {
displayStudent();
} else if (response.equals("C")) {
Student aStudent = createStudent();
if (aStudent != null) {
storeStudentInArray(aStudent);
}
} else if (response.equals("A")) {
gpa();
} else {
messagePane.println("Try again " + initialResponse
+ ", is not a valid choice.\n"
+ "Please enter one of the letters from the specified menu.");
}
} else {
messagePane.println("You must enter one of the letters from the specified menu\n"
+ "before you press \"Enter\".");
}
} while (stillWorking);
}
private Student createStudent() {
messagePane.println(
"\nYou can enter the student's information here: \n");
messagePane.print("What's the Student's name?: ");
String name = keyboard.nextLine();
messagePane.print("What year/grade is the student?: ");
String agrade = keyboard.nextLine();
messagePane.print("Birthday (MMDDYY): ");
int birthday = keyboard.nextInt();
keyboard.nextLine();
messagePane.print("What's their ID number? (1-7 Numbers): ");
String id = keyboard.next();
keyboard.nextLine();
messagePane.print("Course(s) taken: ");
String course = keyboard.nextLine();
double gpa;
messagePane.print("GPA: ");
Scanner inputScanner = new Scanner(keyboard.nextLine());
if (inputScanner.hasNextDouble()) {
gpa = inputScanner.nextDouble();
} else if (inputScanner.hasNext()) {
messagePane.println("You entered something other than a number - the gpa "
+ "has been set to the default of " + Student.DEFAULT_GPA);
gpa = Student.DEFAULT_GPA;
} else {
gpa = Student.DEFAULT_GPA;
}
Student newStudent;
try {
newStudent = Student.create(name,
agrade, birthday, id,
course, gpa );
} catch (Exception anException) {
messagePane.println(" Sorry, I couldn't input the student for you. " + anException.getMessage());
newStudent = null;
}
return newStudent;
}
private void displayStudent() {
Student aStudent = locateStudent();
if (aStudent == null) {
messagePane.println("Sorry, this ID number is not in the classroom.");
} else {
messagePane.println(" " + aStudent.getGrade() + " " + aStudent.getName()
+ " (" + aStudent.getBirthday() + ", " + aStudent.getID() + ") " + "\n"
+ " " + aStudent.getCourse() + " GPA: " + aStudent.getGpa()
);
}
}
private void updateStudent() {
Student aStudent = locateStudent();
if (aStudent == null) {
messagePane.println("Sorry, the student is not listed.");
} else {
updateMenu(aStudent);
}
}
private void updateMenu(Student aStudent) {
assert aStudent != null : "Null parameter supplied to School.updateMenu()";
String studentBeforeUpdating = singleLineStudentDisplay(aStudent);
messagePane.println("The Student being updated is: \n" + aStudent);
boolean stillTrying = true;
do {
messagePane.print("\n"
+ "Student Database Organizer 1.0\n"
+ "UPDATE MENU OPTIONS\n"
+ ""
+ "Press 1 to change the Student's name\n"
+ "Press 2 to update grade\n"
+ "Press 3 to update course(s)\n"
+ "Press 4 to update gpa \n"
+ "Press 5 to finish updating current Student\n"
+ ""
+ "\nPlease enter your selection: ");
Scanner inputScanner = new Scanner(keyboard.nextLine());
if (inputScanner.hasNextInt()) {
int response = inputScanner.nextInt();
if (response == 1) {
updateName(aStudent);
} else if (response == 2) {
updateGrade(aStudent);
} else if (response == 3) {
updateCourse(aStudent);
} else if (response == 4) {
updateGpa(aStudent);
} else if (response == 5) {
stillTrying = false;
} else {
messagePane.println(
"You typed " + response + ", which is not a legit option.\n"
+ "Please check the list of numbers in the menu..");
}
} else if (inputScanner.hasNext()) {
String junk = inputScanner.next();
messagePane.println("You entered " + junk + ", which is not a legal option.\n"
+ "Please enter one of the numbers from the specified menu.");
} else {
messagePane.println("Hold your horses! You need to enter a number\n"
+ "before you press \"Enter\".");
}
} while (stillTrying);
messagePane.println("\n" + "Student before updating: " + studentBeforeUpdating);
messagePane.println("Student after updating: " + singleLineStudentDisplay(aStudent));
}
private void updateName(Student aStudent) {
assert aStudent != null : "Null parameter supplied to School.updateName()";
int result;
messagePane.println("The student's name is: " + aStudent.getName());
messagePane.print("Now it is...: ");
String name = keyboard.nextLine();
result = aStudent.setName(name);
messagePane.println("\nUpdate status: "
+ Student.getDescriptionOfReturnedSignal(result) );
messagePane.println("\nFinalized changes: " + singleLineStudentDisplay(aStudent));
}
private void updateBirthday(Student aStudent) {
assert aStudent != null : "Null parameter supplied to School.updateBirthday()";
int result;
messagePane.println("The current birthday is: " + aStudent.getBirthday());
messagePane.print("New birthday (exactly four digits): ");
Scanner inputScanner = new Scanner(keyboard.nextLine());
if (inputScanner.hasNextInt()) {
int birthday = keyboard.nextInt();
keyboard.nextLine();
result = aStudent.setBirthday(birthday);
messagePane.println("Update status: "
+ Student.getDescriptionOfReturnedSignal(result));
messagePane.println("Finalized Changes: " );
} else {
messagePane.println("You didn't enter a number\n"
+ "Please Check the Format MMDDYY \n\n"
+ "Sorry, no changes were made.");
}
}
private void updateGrade(Student aStudent) {
assert aStudent != null : "Null parameter supplied to School.updateGrade()";
int result;
messagePane.println("The student's grade is: " + aStudent.getGrade());
messagePane.print("Now it is... (at least three characters: ");
String agrade = keyboard.nextLine();
result = aStudent.setGrade(agrade);
messagePane.println("Update status: "
+ Student.getDescriptionOfReturnedSignal(result));
messagePane.println("Finalized Changes: " + singleLineStudentDisplay(aStudent));
}
private void updateCourse(Student aStudent){
assert aStudent != null : "Null parameter supplied to School.updateCourse()";
int result;
messagePane.println("The course(s) taken are: " + aStudent.getCourse());
messagePane.print("Now it is...: ");
String course = keyboard.nextLine();
result = aStudent.setCourse(course);
messagePane.println("Update status: "
+ Student.getDescriptionOfReturnedSignal(result));
messagePane.println("Finalized Changes: " + singleLineStudentDisplay(aStudent));
}
private void updateGpa(Student aStudent){
assert aStudent != null: "Null parameter supplied to School.updateGpa()";
int result;
messagePane.println("GPA is: " + aStudent.getGpa());
messagePane.print("Now it is... (Must be Postive Number): ");
Scanner inputScanner = new Scanner(keyboard.nextLine());
double gpa;
if (inputScanner.hasNextDouble())
{
gpa = keyboard.nextDouble();
}
else
{
messagePane.println("You entered something other than a number - " +
"GPA is back to default " + Student.DEFAULT_GPA);
gpa = Student.DEFAULT_GPA;
}
result = aStudent.setGPA(gpa);
messagePane.println("Update status: " +
Student.getDescriptionOfReturnedSignal(result));
messagePane.println("Finalized Changes" + singleLineStudentDisplay(aStudent));
}
private void gpa() {
int studentCount = nextAvailablePosition;
if (studentCount > 0) {
messagePane.println("\nThe student database has " + studentCount + " student(s):");
messagePane.printf(" %25s, %-35s (%4s, %13s) %-30s %9s \n",
"Grade/Standing", "Student's Name", "Birthday", "ID Number",
"Course(s) taken", "GPA");
int index = 0;
while (index < studentCount) {
Student temp = classroom[index];
messagePane.printf(" %25s, %-35s (%4d, %-13s) %-30s %9.2f \n",
temp.getGrade().length() < 25
? temp.getGrade() : temp.getGrade().substring(0, 25),
temp.getName().length() < 35
? temp.getName() : temp.getName().substring(0, 35),
temp.getBirthday(),
temp.getID(),
temp.getCourse().length() < 30
? temp.getCourse() : temp.getCourse().substring(0, 30),
temp.getGpa());
index++;
}
} else {
messagePane.println("The classroom is currently empty.");
}
}
private Student locateStudent() {
Student aStudent;
messagePane.print("\nEnter the Student's ID you would like to find: ");
Scanner inputScanner = new Scanner(keyboard.nextLine());
if (inputScanner.hasNext()) {
String searchID = inputScanner.next();
aStudent = searchForStudentInArray(searchID);
} else {
messagePane.println("Please enter an ID");
aStudent = null;
}
return aStudent;
}
private String singleLineStudentDisplay(Student aStudent) {
assert aStudent != null : "Null parameter supplied to School.singleLineStudentDisplay()";
return aStudent.getGrade() + ", " + aStudent.getName() + " ("
+ aStudent.getID() + ", " + aStudent.getBirthday() + ") "
+ aStudent.getCourse() + " GPA: " + aStudent.getGpa();
}
}
Here is Student :
package student;
public class Student {
public static final int SET_SUCCESSFUL = 0;
public static final int GRADE_CANNOT_BE_NULL = -1;
public static final int GRADE_CANNOT_BE_EMPTY = -2;
public static final int GRADE_MUST_BE_AT_LEAST_SIX_CHARACTERS = -3;
public static final int NAME_CANNOT_BE_NULL = -11;
public static final int NAME_CANNOT_BE_EMPTY = -12;
public static final int BIRTHDAY_MUST_BE_EXACTLY_SIX_DIGITS_CHECK_FORMAT = -24;
public static final int ID_MUST_BE_ONE_OR_SEVEN_NUMBERS = -31;
public static final int ID_CANNOT_BE_NULL = -32;
public static final int ID_CANNOT_BE_EMPTY = -33;
public static final int COURSE_CANNOT_BE_EMPTY = -41;
public static final int GPA_CANNOT_BE_NEGATIVE = -51;
public static final double DEFAULT_GPA = 0.0;
private String name;
private String grade;
private int birthday;
private String id;
private String course;
private double gpa;
private Student() {
super();
}
public static Student create(String theName,
String theGrade, int theBirthday,String theId,
String theCourse, double theGpa) throws Exception {
Student newStudent = new Student();
int result;
result = newStudent.setName(theName);
if (result != SET_SUCCESSFUL) {
throw new Exception(Student.getDescriptionOfReturnedSignal(result));}
result = newStudent.setGrade(theGrade);
if (result != SET_SUCCESSFUL) {
throw new Exception(Student.getDescriptionOfReturnedSignal(result));}
result = newStudent.setBirthday(theBirthday);
if (result != SET_SUCCESSFUL) {
throw new Exception(Student.getDescriptionOfReturnedSignal(result));}
result = newStudent.setId(theId);
if (result != SET_SUCCESSFUL) {
throw new Exception(Student.getDescriptionOfReturnedSignal(result));}
result = newStudent.setCourse(theCourse);
if (result != SET_SUCCESSFUL) {
throw new Exception(Student.getDescriptionOfReturnedSignal(result));}
result = newStudent.setGPA(theGpa);
if (result != SET_SUCCESSFUL) {
throw new Exception(Student.getDescriptionOfReturnedSignal(result));}
return newStudent;}
// <editor-fold defaultstate="collapsed" desc="------------------------------------------------------------------------------"> /* */
// </editor-fold>
public String getName() {
return name;}
public String getGrade() {
return grade;}
public int getBirthday() {
return birthday;}
public String getID() {
return id;}
public String getCourse() {
return course;}
public double getGpa() {
return gpa;}
@Override
public String toString() {
StringBuilder temp = new StringBuilder(name);
temp.append("\nwho is a ");
temp.append(grade);
temp.append("\nwith a Birthday on ");
temp.append(birthday);
temp.append("\nID Number ");
temp.append(id);
temp.append("\nwho takes ");
temp.append(course);
temp.append("\nwith a GPA of ");
temp.append(gpa);
temp.append(' ');
return temp.toString();
}
public static String getDescriptionOfReturnedSignal(int aSignal) {
if (aSignal == SET_SUCCESSFUL) {
return "SET_SUCCESSFUL";}
if (aSignal == GRADE_CANNOT_BE_NULL) {
return "GRADE_CANNOT_BE_NULL";}
if (aSignal == GRADE_CANNOT_BE_EMPTY) {
return "GRADE_CANNOT_BE_EMPTY";}
if (aSignal == GRADE_MUST_BE_AT_LEAST_SIX_CHARACTERS) {
return "GRADE_MUST_BE_AT_LEAST_SIX_CHARACTERS";}
if (aSignal == NAME_CANNOT_BE_NULL) {
return "NAME_CANNOT_BE_NULL";}
if (aSignal == NAME_CANNOT_BE_EMPTY) {
return "NAME_CANNOT_BE_EMPTY";}
if (aSignal == BIRTHDAY_MUST_BE_EXACTLY_SIX_DIGITS_CHECK_FORMAT) {
return "BIRTHDAY_MUST_BE_EXACTLY_SIX_DIGITS_CHECK_FORMAT";}
if (aSignal == ID_CANNOT_BE_NULL) {
return "ID_CANNOT_BE_NULL";}
if (aSignal == ID_CANNOT_BE_EMPTY) {
return "ID_CANNOT_BE_EMPTY";}
if (aSignal == ID_MUST_BE_ONE_OR_SEVEN_NUMBERS) {
return "ID_MUST_BE_ONE_OR_SEVEN_NUMBERS";}
if (aSignal == COURSE_CANNOT_BE_EMPTY) {
return "COURSE_CANNOT_BE_EMPTY";}
if (aSignal == GPA_CANNOT_BE_NEGATIVE) {
return "GPA_CANNOT_BE_NEGATIVE";}
return "Sorry, but the signal value " + aSignal + " is not recognized.";
}
public int setName(String theName) {
if (theName == null) {
return NAME_CANNOT_BE_NULL;
}
String trimmedName = theName.trim();
if (trimmedName.isEmpty()) {
return NAME_CANNOT_BE_EMPTY;
}
name = trimmedName;
return SET_SUCCESSFUL;
}
public int setGrade(String theGrade) {
if (theGrade == null) {
return GRADE_CANNOT_BE_NULL;
}
String trimmedGrade = theGrade.trim();
if (trimmedGrade.isEmpty()) {
return GRADE_CANNOT_BE_EMPTY;
}
if (trimmedGrade.length() < 6) {
return GRADE_MUST_BE_AT_LEAST_SIX_CHARACTERS;
}
grade = trimmedGrade;
return SET_SUCCESSFUL;
}
public int setBirthday(int theBirthday) {
if (theBirthday <= 7) {
return BIRTHDAY_MUST_BE_EXACTLY_SIX_DIGITS_CHECK_FORMAT;
}
birthday = theBirthday;
return SET_SUCCESSFUL;
}
private int setId(String theId) {
if (theId == null) {
return ID_CANNOT_BE_NULL;
}
String trimmedId = theId.trim();
if (trimmedId.isEmpty()) {
return ID_CANNOT_BE_EMPTY;
}
if (trimmedId.length() != 1 && trimmedId.length() != 7) {
return ID_MUST_BE_ONE_OR_SEVEN_NUMBERS;
}
id = trimmedId;
return SET_SUCCESSFUL;
}
public int setCourse(String theCourse) {
if (theCourse == null) {
course = "";
return SET_SUCCESSFUL;
}
String trimmedCourse = theCourse.trim();
if (trimmedCourse.isEmpty()) {
return COURSE_CANNOT_BE_EMPTY;
}
course = trimmedCourse;
return SET_SUCCESSFUL;
}
public int setGPA(double theGPA) {
if (theGPA < 0.0) {
return GPA_CANNOT_BE_NEGATIVE;
}
gpa = theGPA;
return SET_SUCCESSFUL;
}
/*
public String getbirthday() {
throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates.
}
*/
}
