I'm building a university management system where admin can log in, add student, department, 2ndly there is a faculty panel and lastly, there is a student panel where they can set course. But I've been facing some problems after adding a new student through the admin panel. The problem is if want to exit from the admin panel the whole program close. Is there any solution that if I exit from admin panel I should get back to main menu where i can enter in any panel again. there is one more problem if i tried to remove a student from registered it shows not found. Can anyone help me through this problem?
Here is my code MainActivity.java
import java.util.Scanner;
import mainpanel.*;
import interfacepart.*;
//import transactionpart.*;
public class MainActivity{
public static void main(String args[]){
boolean flag = true;
Student[] student1 = new Student[2000];
Scanner sc = new Scanner(System.in);
Admin a = new Admin("Admin", "1234");
System.out.println("**********Welcome to University Management*******");
//do {
System.out.println("**********Please Choose the task you want to perform****");
System.out.println("1.Adming Login");
System.out.println("2.Faculty Login");
System.out.println("3.Student Login");
int choose = sc.nextInt();
sc.nextLine();
if(choose == 1){
Scanner ac = new Scanner(System.in);
System.out.println("**********Welcome to Admin panel*******");
System.out.println("Please enter the userName: ");
String user = sc.nextLine();
System.out.println("Please enter the password: ");
String password = sc.nextLine();
if("Admin".equals(user) && "1234".equals(password)){
do{
System.out.println("Login successful");
System.out.println ( "**** 1. add students and department *****");
System.out.println ( "**** 2. remove students *****");
System.out.println ( "**** 3. student Information *****");
//System.out.println ( "**** n 5, print student *****");
System.out.println ( "**** 4, exit the system *****");
int sel = sc.nextInt();
switch (sel){
case 1:
System.out.println("Enter the number of student you want to add: ");
int num = sc.nextInt();
sc.nextLine();
for (int i = 0; i<num; i++) {
if (student1[i] == null) {
System.out.println("Enter the deptname: ");
String depntName = sc.nextLine();
System.out.println("Enter the deptId: ");
String depntId = sc.nextLine();
System.out.println("Enter the totalCredit: ");
int totalCredit = sc.nextInt();
sc.nextLine();
Department cs = new Department(depntName, depntId, totalCredit);
Scanner mc = new Scanner(System.in);
System.out.println("Enter the StudentName: ");
String StudentName = mc.nextLine();
System.out.println("Enter the StudentId: ");
String StudentId = mc.nextLine();
System.out.println("Enter the StudentAge: ");
String StudentAge = mc.nextLine();
System.out.println("Enter the email: ");
String email = mc.nextLine();
System.out.println("Enter the bloodGroup: ");
String bloodGroup = mc.nextLine();
System.out.println("Enter the phoneNumber: ");
String phoneNumber = mc.nextLine();
System.out.println("Enter the Address: ");
String Address = mc.nextLine();
mc.nextLine();
Student s1 = new Student(StudentName,StudentId,StudentAge,email,bloodGroup,phoneNumber,Address);
student1[i] = s1;
a.addNewRegister(student1[i]);
a.addNewDepartment(cs);
student1[i].SetAdmin(a);
student1[i].SetDeparment(cs);
cs.addNewRegister(student1[i]);
//break;
}
else{
System.out.println ( "Number of students in full");
break;
}
}
break;
case 2:
boolean isStudentRegistered = false;
System.out.println("Please Enter the Id you want to remove: ");
Scanner newCheck = new Scanner(System.in);
String stdId = newCheck.nextLine();
for(Student total : student1){
if(total != null){
if(total.getId() == stdId){
System.out.println("student found");
isStudentRegistered = true;
total = null;
System.out.println("Student removed");
}
}
}if(!isStudentRegistered){
System.out.println("No student found");
}
break;
case 3:
for(int i=0; i<1; i++){
a.showRegisteredInfo();
break;
}
break;
case 4:
System.exit(0);
//flag = false;
//break;
//continue;
break;
default:
break;
}
}while (true);
} else {
//flag = true;
System.out.println ( "Login failed please re-enter:");
}
}
else if(choose == 3){
Scanner std = new Scanner(System.in);
System.out.println ( "Welcome to Student Panel*******");
System.out.println("Please enter the StudentId: ");
String userId = std.nextLine();
System.out.println("Please enter the password: ");
String password = std.nextLine();
do{
for(Student total : student1){
if(total != null){
if(total.getId() == userId){
System.out.println("*********Welcome to university Portal***");
//isStudentRegistered = true;
total.showInfo();
}else{
System.out.println("You are not registered yet");
}
}
}
}while(true);
}
else{
System.out.println ( "Login failed please re-enter:");
}
/*} while (true);
}*/
}
}
Admin.java
package mainpanel;
public class Admin{
protected String userName;
protected String passWord;
Student[] addNewStudent;
Department[] department;
Courses[] courses;
int totalRegisterCount;
int totalDepartmentCount;
int totalCourseCount;
public Admin(){
addNewStudent = new Student[200];
department = new Department[10];
courses = new Courses[200];
totalRegisterCount = 0;
totalDepartmentCount = 0;
totalCourseCount = 0;
}
public Admin(String userName, String passWord){
this.userName = userName;
this.passWord = passWord;
addNewStudent = new Student[200];
department = new Department[10];
courses = new Courses[200];
totalRegisterCount = 0;
totalDepartmentCount = 0;
totalCourseCount = 0;
}
public void SetUserName(String userName){
this.userName = userName;
}
public String GetUserName(){
return userName;
}
public void SetpassWord(String passWord){
this.userName = userName;
}
public String GetPassword(){
return passWord;
}
public void addNewRegister(Student NewStudent){
addNewStudent[totalRegisterCount++] = NewStudent;
}
//public void removeNewStudent(Student removeNewStudent){
//}
public void addNewDepartment(Department dept){
department[totalDepartmentCount++] = dept;
}
public void addNewCourse(Courses crs){
courses[totalCourseCount++] = crs;
}
public void showDepartmentInfo(){
for(int i=0; i<totalDepartmentCount; i++){
department[i].showInfo();
}
}
public void showRegisteredInfo(){
for(int i=0; i<totalRegisterCount; i++){
addNewStudent[i].showInfo();
//addNewStudent[i].AllCourseInfo();
}
}
public void searchStudentInfo(String stdId){
//department[num].showInfo();
boolean isStudentRegistered = false;
for(Student total : addNewStudent){
if(total != null){
if(total.getId() == stdId){
System.out.println("student found");
isStudentRegistered = true;
total.showInfo();
}
}
}
if(!isStudentRegistered){
System.out.println("No student found");
}
}
/*
public void removeStudentInfo(String stdId){
//department[num].showInfo();
boolean isStudentRegistered = false;
for(Student total : addNewStudent){
if(total != null){
if(total.getId() == stdId){
System.out.println("student found");
isStudentRegistered = true;
total = null;
System.out.println("Student removed");
}
}
}
if(!isStudentRegistered){
System.out.println("No student found");
}
}
*/
}
//courses[num].showInfo();
/*public void showCourseInfo(){
for(int i=0; i<totalCourseCount; i++){
courses[i].showInfo();
}
}
*/
Approach 1 - Not recommended
You can either have a loop surrounding the core functionality of your application and break out of any internal loops to go back to the beginning of the core loop.
Approach 2 - Recommended
You could refrain from using a core loop and refactor your code such that each menu interaction is a separate function.
Each function would present the user with a specific menu and depending on the user's input another function would be called for the next menu. Generally speaking, you would not require any loops to keep the application running.
This would reduce the complexity and confusion of your code and make it much easier to expand the application with new features without needing to concern yourself with where to place code within the loop.
I recommend reading up on SOLID design principles to get an idea of how best to structure code. Here is an example article. This answer and example code is not meant to be a full representation of SOLID design and I would recommend that you strongly consider using interfaces and separate classes for each distinct part of the system and not having all the code in the MainActivity class.
An example of a function-based approach would be as follows.
I mainly focussed on the Main Menu and Admin Menu. The principle can be applied across the entire application.
Scanner sc = new Scanner(System.in);
private void displayMainMenu() {
System.out.println("**********Please Choose the task you want to perform****");
System.out.println("1.Admin Login");
System.out.println("2.Faculty Login");
System.out.println("3.Student Login");
int input = sc.nextInt();
sc.nextLine();
switch (input) {
case 1:
displayAdminLoginMenu();
break;
case 2:
displayFacultyLoginMenu();
break;
case 3:
displayStudentLoginMenu();
break;
default:
// Display the main menu again if no option was successful.
// Can also handle possible errors here with feedback to the user.
displayMainMenu();
break;
}
}
private void displayAdminLoginMenu() {
// Perform login operation here
// After successful login display admin options menu
displayAdminOptionsMenu();
}
private void displayFacultyLoginMenu() {
}
private void displayStudentLoginMenu() {
}
private void displayAdminOptionsMenu() {
System.out.println("**** 1. add students and department *****");
System.out.println("**** 2. remove students *****");
System.out.println("**** 3. student Information *****");
System.out.println("**** 4, return to main menu *****");
System.out.println("**** 5, exit the system *****");
int input = sc.nextInt();
switch (input) {
case 1:
// Call function for option 1.
break;
case 2:
// Call function for option 2.
break;
case 3:
// Call function for option 3.
break;
case 4:
displayMainMenu();
break;
case 5:
exitApplication();
break;
default:
// Display the admin menu again if no option was successful.
// Can also handle possible errors here with feedback to the user.
displayAdminOptionsMenu();
break;
}
}
private void exitApplication() {
System.exit(0);
}
These are not necessarily the only options available, but they are what I could think of at the moment.
package trainbooking;
import java.util.Scanner;
public class Trainbooking {
static final int SEATING_CAPACITY = 8;
public static void displayMenu() {
System.out.println("WELCOME TO OUR BOOKING SYSTEM");
System.out.println("A) Add a customer to seat");
System.out.println("V) View all the seats");
System.out.println("E) Display Empty seats");
System.out.println("D) Delete customer from seat");
System.out.println("F) Find the seat for a given customers name");
System.out.println("S) Store program data in to file");
System.out.println("L) Load program data from file");
System.out.println("O) View seats Ordered alphabetically by name");
System.out.println("Q) Exit the application\n");
}
public static void V(String[]seats) {
for (int i = 0; i < seats.length; i++) {
System.out.println(seats[i]);
}
}
public static void A(String[]seats) {
Scanner input = new Scanner(System.in);
System.out.println("What is the name of the customer you want to add? ");
String customerName = input.next();
System.out.println("What seat number do you want this customer to have?");
int seatNumber = input.nextInt();
seats[seatNumber] = customerName;
System.out.println("Thank you, your record was submitted.");
}
public static void E() {
// System.out.println("Empty seats");
//for(int i=0;<seats.length;i++){
// System.out.println("current seat"+ " is ressrved by" + seats[i]);
// }
}
public static void D() {}
public static void F() {}
public static void S() {}
public static void L() {}
public static void O() {
int name;
String temp;
Scanner input = new Scanner(System.in);
System.out.print("Enter all of the pessenger names below; ");
name = input.nextInt();
String names[] = new String[name];
Scanner b1 = new Scanner(System.in);
System.out.println("Enter all the names:");
for (int i = 0; i < name; i++) {
names[i] = b1.nextLine();
}
for (int i = 0; i < name; i++) {
for (int j = i + 1; j < name; j++) {
if (names[i].compareTo(names[j]) > 0) {
temp = names[i];
names[i] = names[j];
names[j] = temp;
}
}
}
System.out.print("Following pessenger names have been Sorted in Order:");
for (int i = 0; i < name - 1; i++) {
System.out.print(names[i] + ",");
}
System.out.print(names[name - 1]);
}
}
public static void main(String[]args) {
String[]seats = new String[SEATING_CAPACITY];
Scanner in = new Scanner(System.in);
char choice;
do {
displayMenu();
System.out.println("Enter a choice or press q to quit the application");
choice = in.next().toUpperCase().charAt(0);
switch (choice) {
case 'A':
A(seats);
break;
case 'V':
V(seats);
break;
case 'E':
E();
break;
case 'D':
D();
break;
case 'F':
F();
break;
case 'S':
S();
break;
case 'L':
L();
break;
case 'O':
O();
break;
default:
System.out.println("You have entered the wrong choice. Please try again!");
}
} while ((choice != 'Q'));
System.out.println("Thank you for using our system.");
}
}
You are probably expecting a String/Text input at this function.
But what you do is the following:
You call the function Scanner.nextInt() which tries to read an Integer/Number value from the console.
What you should do instead of input.nextInt() use input.nextLine() and it shouldn't crash anymore.
In my code below I am not sure what order to put it in to work properly.
I first want it to print out for the user to select an option which it does, then if they select 1 it asks them their name and verifies it with the loop etc.
When I enter a name it starts to just loop the question enter your name and I don't know how to fix it.
Do I need to add more statements to my program, if I do then can I still use if statements for the user to select an option?
import java.util.Scanner;
public class username {
public static void main(String[] args) {
{
int UseLift;
int AuditReport;
int ExitLift;
int a;
UseLift = 1;
AuditReport = 2;
ExitLift = 3;
}
System.out.println("choose an option");
System.out.println("Uselift(1)");
System.out.println("see audit report(2)");
System.out.println("Exit Lift(3)");
Scanner d = new Scanner(System.in);
int a = d.nextInt();
Scanner kb = new Scanner(System.in);
// array containing usernames
String[] name = {"barry", "matty", "olly", "joey"}; // elements in array
if (a == 1) {
System.out.println(" Enter your name ");
}
String name1 = kb.nextLine();
boolean b = true;
int j = 0;// counter will start at 0
outerloop:
while (j < 3) {
System.out.println("Enter your name");
}
for (int i = 0; i < name.length; i++) {
if (name[i].equals(name1)) {
System.out.println("you are verified you may use the lift, calling lift ");
}
break;// to stop loop checking names
}
System.out.println("Username Invalid");
j++;
if (a == 2) {
System.out.println("");
}
if (a == 3) {
System.out.println(" Please Exit Lift ");
}
}
}
here you go:
public static void main(String... args) {
String[] verifiedNames = { "barry", "matty", "olly", "joey" };
System.out.println("choose an option");
System.out.println("Uselift(1)");
System.out.println("see audit report(2)");
System.out.println("Exit Lift(3)");
Scanner scanner = new Scanner(System.in);
int choice = scanner.nextInt();
switch (choice) {
case 1:
scanner.nextLine(); // get '\n' symbol from previous input
int nameAttemptsLeft = 3;
while (nameAttemptsLeft-- > 0) {
System.out.println(" Enter your name ");
String name = scanner.nextLine();
if (Arrays.asList(verifiedNames).contains(name)) {
System.out.println("dear " + name + " you are verified " +
"you may use the lift, calling lift ");
break; // break out of loop
}
}
if (nameAttemptsLeft < 0) {
System.out.println("Username Invalid");
}
break;
case 2:
System.out.println("option 2");
break;
case 3:
System.out.println(" Please Exit Lift ");
break;
}
scanner.close();
}
Your while loop below:
while (j < 3) {
System.out.println("Enter your name");
}
will loop forever since j is not incrementing (j++). I believe you've mis-matched your curly braces at some point.
I have four classes but they're just templates so I'll only post my main class (I have overridden toString for each). The sort method is at the bottom. Everything else is fine (more or less) with my code, but when I create the objects in the array and then go to sort them (by a string value called uid) sometimes one or two of them will be out of order. How can I fix this?
Here's the code:
import java.io.File;
import java.io.FileNotFoundException;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.InputMismatchException;
import java.util.Scanner;
enum ClassStanding{FRESHMAN,SOPHOMORE,JUNIOR,SENIOR,UNKNOWN,MASTERS_STUDIES,PHD_STUDIES};
enum Major{CS,CEG,EE,ISE,BME,ME,MET,UNKNOWN};
enum StudentType{UNDERGRADUATE,GRADUATE,UNDECLARED};
public class Main {
/**
* #param args the command line arguments
*/
public static void main(String[] args) {
Scanner stdin = new Scanner(System.in);
ArrayList<Student> studentList = new ArrayList<>();
int counter;
boolean continueInput;
int contCounter;
do {
do {
System.out.print("Please enter what you want to do-ADD, REMOVE, SORT, LIST, or SAVE: ");
switch (stdin.next().toLowerCase()) {
case "add":
add(stdin, studentList);
counter = 0;
break;
case "remove":
remove(studentList, stdin);
counter = 0;
break;
case "list":
list(studentList);
counter = 0;
break;
case "save":
String fileName = getFileName(stdin);
save(fileName, studentList);
counter = 0;
break;
case "sort":
counter = 0;
sort(studentList);
break;
default:
System.out.println("Improper input, please enter only ADD, REMOVE, LIST, or SAVE.");
counter = 1;
}
} while (counter == 1);
do {
System.out.print("\nDo you want to continue? Yes or no: ");
switch (stdin.next().toLowerCase()) {
case "yes":
contCounter = 0;
continueInput = true;
break;
case "no":
contCounter = 0;
continueInput = false;
break;
default:
contCounter = 1;
continueInput = false;
System.out.print("\nPlease only enter 'yes' or 'no'.");
}
} while (contCounter == 1);
} while (continueInput);
} // end main method
public static void add(Scanner stdin, ArrayList<Student> studentList) {
String firstName;
String lastName;
String uid;
StudentType studentType;
ClassStanding studentClassStanding;
Major major;
double overallGPA;
double majorGPA;
String majorProfessor;
boolean thesisOption;
System.out.print("Please enter the student's first name: ");
String tempName = stdin.next();
firstName = checkName(tempName);
System.out.print("Please enter the student's last name: ");
tempName = stdin.next();
lastName = checkName(tempName);
System.out.println("Please enter the student's UID in the format 'U####' or 'U#####': ");
String tempUID = stdin.next();
uid = checkUID(tempUID).toUpperCase();
int count;
do {
System.out.print("Please enter the student's status as UNDECLARED, UNDERGRADUATE, or GRADUATE: ");
switch (stdin.next().toUpperCase()) {
case "UNDECLARED":
studentType = StudentType.UNDECLARED;
studentClassStanding = setStudentClassStanding(studentType);
count = 0;
Student student = new Student(firstName, lastName,
uid, studentType, studentClassStanding);
studentList.add(student);
break;
case "UNDERGRADUATE":
studentType = StudentType.UNDERGRADUATE;
major = setMajor();
studentClassStanding = setStudentClassStanding(studentType);
System.out.println("Enter the student's overall GPA below.");
overallGPA = setGPA();
System.out.println("Enter the student's major GPA below.");
majorGPA = setGPA();
count = 0;
UnderGraduate underGraduate = new UnderGraduate(firstName, lastName, uid, studentType,
studentClassStanding, major, overallGPA, majorGPA);
studentList.add(underGraduate);
break;
case "GRADUATE":
studentType = StudentType.GRADUATE;
studentClassStanding = setStudentClassStanding(studentType);
majorProfessor = setMajorProfessor();
thesisOption = setThesisOption();
count = 0;
Graduate graduate = new Graduate(firstName, lastName, uid, studentType,
studentClassStanding, majorProfessor, thesisOption);
studentList.add(graduate);
break;
default:
System.out.println("Please enter either Undeclared, Undergraduate, or Graduate only.");
count = 1;
}
} while (count == 1);
} // end add method
public static String checkName(String tempName) {
int a = 1;
String name1;
Scanner scanner = new Scanner(System.in);
do {
name1 = tempName; // hold the value of firstName in name1
for (int i = 0; i < tempName.length(); i++) { // loop to check input consists of letters (is a name)
if (!Character.isLetter(tempName.charAt(i))) { // if non-letters detected, ensure this was intentional
System.out.println("Please ensure you've entered the correct name. Re-enter the name or enter 'continue' to proceed: ");
tempName = scanner.nextLine();
if (tempName.equalsIgnoreCase("continue")) { // if user enters "continue", use original input
a = 0;
tempName = name1; // pass name1 value to firstName
break;
} else {
a = 1; // continue prompting for firstName
}
} else { // accept input
a = 0;
}
}
} while (a == 1); // loop to ensure proper input
return tempName;
} // end checkName method
public static String checkUID(String tempUID) {
Scanner scan = new Scanner(System.in);
int a;
do {
if (tempUID.charAt(0) == 'U' || tempUID.charAt(0) == 'u') {
if (tempUID.length() == 6 || tempUID.length() == 5) {
a = 0;
} else {
a = 1;
System.out.print("Please ensure input is in the form of U#### or U#####. Please re-enter the UID: ");
tempUID = scan.next();
}
} else {
a = 1;
System.out.print("Please ensure input is in the form of U#### or U#####. Please re-enter the UID: ");
tempUID = scan.next();
}
} while (a == 1);
return tempUID;
} // end checkUID method
public static ClassStanding setStudentClassStanding(StudentType studentType) {
Scanner scan = new Scanner(System.in);
int count;
ClassStanding studentTempClassStanding = null;
do {
if (studentType == StudentType.UNDECLARED || studentType == StudentType.UNDERGRADUATE) {
System.out.print("Please enter the student's class standing as either Freshman, Sophomore, Junior, Senior, or Unknown: ");
switch (scan.next().toUpperCase()) {
case "FRESHMAN":
studentTempClassStanding = ClassStanding.FRESHMAN;
count = 0;
break;
case "SOPHOMORE":
studentTempClassStanding = ClassStanding.SOPHOMORE;
count = 0;
break;
case "JUNIOR":
studentTempClassStanding = ClassStanding.JUNIOR;
count = 0;
break;
case "SENIOR":
studentTempClassStanding = ClassStanding.SENIOR;
count = 0;
break;
case "UNKNOWN":
studentTempClassStanding = ClassStanding.UNKNOWN;
count = 0;
break;
default:
System.out.println("Please enter only Freshman, Sophomore, Junior, Senior, or Unknown.");
count = 1;
}
} else {
System.out.print("Please enter the student's class standing as either 'Masters' for Masters Studies or 'PhD' for PhD Studies: ");
switch (scan.next().toUpperCase()) {
case "MASTERS": studentTempClassStanding = ClassStanding.MASTERS_STUDIES; count = 0; break;
case "PHD": studentTempClassStanding = ClassStanding.PHD_STUDIES; count = 0; break;
default: System.out.println("Please enter only 'Masters' or 'PhD'.");
count = 1;
}
}
} while (count == 1);
return studentTempClassStanding;
} // end setStudentClassStanding method
public static Major setMajor() {
Major tempMaj = null;
Scanner s = new Scanner(System.in);
int c;
do {
System.out.print("Please enter the student's major as either CS, CEG, EE, ISE, BME, ME, MET, or Unknown: ");
switch (s.next().toUpperCase()) {
case "CS":
tempMaj = Major.CS;
c = 0;
break;
case "CEG":
tempMaj = Major.CEG;
c = 0;
break;
case "EE":
tempMaj = Major.EE;
c = 0;
break;
case "ISE":
tempMaj = Major.ISE;
c = 0;
break;
case "BME":
tempMaj = Major.BME;
c = 0;
break;
case "ME":
tempMaj = Major.ME;
c = 0;
break;
case "MET":
tempMaj = Major.MET;
c = 0;
break;
case "UNKOWN":
tempMaj = Major.UNKNOWN;
c = 0;
break;
default:
System.out.println("Please enter only the specified values. ");
c = 1;
}
} while (c == 1);
return tempMaj;
} // end setMajor method
public static double setGPA() {
Scanner s = new Scanner(System.in);
double gpa;
int a;
do {
try {
System.out.print("Please enter the student's GPA: ");
gpa = s.nextDouble();// read in the gpa
if (gpa < 0.0 || gpa > 4.0) { // ensure the gpa is in the correct range
System.out.println("Invalid input, please enter a positive value between 0.0 and 4.0.");
a = 1;
} else {
a = 0;
}
} catch (InputMismatchException ex) { //catch any exceptions, prompt for correct input
a = 1;
gpa = 0.0;
System.out.println("Sorry, please enter a double value.");
s.nextLine(); // skip the last input
}
} while (a == 1 || gpa < 0.0 || gpa > 4.0); //loop while gpa is negative or incorrect input is received
return gpa;
} // end setGPA method
private static String setMajorProfessor() {
Scanner s = new Scanner(System.in);
String prof;
System.out.print("Please enter the name of the major professor: ");
String tempName = s.nextLine();
prof = checkName(tempName);
return prof;
} // end setMajorProfessor method
private static boolean setThesisOption() {
Scanner s = new Scanner(System.in);
boolean thesis = false;
int a;
do {
System.out.print("Please enter 'yes' if a thesis will be written, otherwise enter 'no': ");
switch (s.next().toUpperCase()) {
case "YES": thesis = true; a = 0; break;
case "NO": thesis = false; a = 0; break;
default: System.out.println("Please enter only 'yes' or 'no'."); a = 1;
}
} while (a == 1);
return thesis;
} // end setThesisOption method
private static void list(ArrayList<Student> studentList) {
for (int i = 0; i < studentList.size(); i++) {
System.out.println(studentList.get(i).toString());
}
} // end list method
public static String getFileName(Scanner stdin) {
System.out.print("Please enter the file name: "); // Prompt for input
String fileString = stdin.next();
return fileString; // Pass the fileString var to the main method
}//end of getFileName method
private static void save(String fileName, ArrayList<Student> studentList) {
int a; // create a counter
Scanner stdin = new Scanner(System.in);
do {
try {
PrintWriter writer = new PrintWriter(fileName); // Create a printwriter
for (int i = 0; i < studentList.size(); i++) {
writer.print(studentList.get(i).toString() + "\n"); //Print the arraylist to file
}
writer.close(); //Close the printwriter and save the file
a = 0;
} catch (FileNotFoundException ex) { // Catch any exceptions
System.out.println("The file could not be found, please re-enter the file name: "); // get new file name if an exception is thrown
fileName = stdin.nextLine();
a = 1;
}
} while (a == 1); // loop while exceptions are thrown
System.out.println("All information has been saved at " + fileName); // output that the arraylist has been saved in the specified file
// Make the following its own method
System.out.print("Would you like to read the contents of the file? Yes or no: ");
int b;
do {
switch (stdin.next().toLowerCase()) {
case "yes": readFromFile(fileName); b = 0; break;
case "no": b = 0; break;
default: System.out.println("Please enter only yes or no."); b = 1;
}
} while (b == 1);
} // end save method
private static void remove(ArrayList<Student> studentList, Scanner stdin) {
System.out.print("Please enter the UID of the student to be removed: ");
String tempUID = stdin.next();
String uidRemove = checkUID(tempUID);
for (int i = 0; i < studentList.size(); i++) {
if ((studentList.get(i).getUid()).equalsIgnoreCase(uidRemove)) {
studentList.remove(i);
}
}
System.out.println("The student with UID " + uidRemove + " has been removed.");
} // end remove method
private static void sort(ArrayList<Student> studentList) {
String uidLessU1;
String uidLessU2;
for (int i = 0; i < studentList.size(); i++) {
uidLessU1 = (studentList.get(i).getUid()).substring(1, studentList.get(i).getUid().length());
for (int j = 0; j < studentList.size(); j++) {
uidLessU2 = (studentList.get(j).getUid()).substring(1, studentList.get(j).getUid().length());
if (Integer.parseInt(uidLessU1) < Integer.parseInt(uidLessU2)) {
Student hold = studentList.get(i);
studentList.set(i, studentList.get(j));
studentList.set(j, hold);
}
}
}
} // end sort method
private static void readFromFile(String fileName) {
System.out.println("The contents of " + fileName + " as read from NotePad: ");
try {
Scanner fileReader = new Scanner(new File(fileName)); //Create a scanner
while (fileReader.hasNextLine()) { //Loop to read the file
String fromFile = fileReader.nextLine();
System.out.println(fromFile); //Output the file contents
}
} catch (FileNotFoundException ex) { //Catch any exceptions
System.out.println("Exception caught");
}
} // end readFromFile method
} // end main class
A sample of the problem would be (at this point I've already entered all the values instantiating the objects):
Do you want to continue? Yes or no: yes
Please enter what you want to do-ADD, REMOVE, SORT, LIST, or SAVE: list
Student s w whose UID is U3333 is a
UNDECLARED student doing JUNIOR work.
Student p o whose UID is U1111 is a
UNDECLARED student doing JUNIOR work.
Student p u whose UID is U44444 is a
UNDECLARED student doing JUNIOR work.
Student w e whose UID is U4444 is a
UNDECLARED student doing JUNIOR work.
Student s r whose UID is U2222 is a
UNDECLARED student doing JUNIOR work.
Student s u whose UID is U7777 is a
UNDECLARED student doing JUNIOR work.
Student po iu whose UID is U77777 is a
UNDECLARED student doing JUNIOR work.
Do you want to continue? Yes or no: yes
Please enter what you want to do-ADD, REMOVE, SORT, LIST, or SAVE: sort //calls the sort method
Do you want to continue? Yes or no: yes
Please enter what you want to do-ADD, REMOVE, SORT, LIST, or SAVE: list // calls the list method and prints out the arraylist
Student p o whose UID is U1111 is a
UNDECLARED student doing JUNIOR work.
Student s r whose UID is U2222 is a
UNDECLARED student doing JUNIOR work.
Student s w whose UID is U3333 is a
UNDECLARED student doing JUNIOR work.
Student s u whose UID is U7777 is a //why is this out of place?
UNDECLARED student doing JUNIOR work.
Student w e whose UID is U4444 is a
UNDECLARED student doing JUNIOR work.
Student p u whose UID is U44444 is a
UNDECLARED student doing JUNIOR work.
Student po iu whose UID is U77777 is a
UNDECLARED student doing JUNIOR work.
Just make Student implement Comparable and then you can do
Collections.sort(studentList);
This question already has an answer here:
my input array keeps over writing itself
(1 answer)
Closed 9 years ago.
My current problem contains two arrays, everytime i enter a book, the book ID goes up one. This seems to work ok. But my current issue is that when i put in a new book, it completely over writes the last entry. eg John smith BookID1 could be my first entry. But then i add Penny Jones BookID2 , the john smith disappears.
To try resolve this i have added static int location = 0 in the class and also changed this is the array entry but it still not working.
import java.util.Scanner;
public class library {
static Scanner keyboard = new Scanner(System.in);
static boolean run = true;
static int location = 0;
public static fiction [] fictionArray = new fiction[2];
public static nonfiction [] nonfictionArray = new nonfiction[2];
public static void main (String[] args){ // main class method
while (run){ // this while statement allows the menu to come up again
int answer = 0; // answer initialized to Zero
boolean isNumber;
do{ // start of validation
System.out.println("1. Add book"); // Menu selections
System.out.println("2. Display the books available for loan");
System.out.println("3. Display the books currently on loan");
System.out.println("4. Make a book loan");
System.out.println("5. Return book ");
System.out.println("6 Write book details to file");
if (keyboard.hasNextInt()){ // I would like to set values to =>1 <=6
answer = keyboard.nextInt(); // this is more validation for the input for menu selection
isNumber = true;
} else { // else if number not entered, it will prompt for the correct input
System.out.print(" You must enter a number from the menu to continue. \n");
isNumber = false;
keyboard.next(); // clears keyboard
}
}
while (!(isNumber)); // while to continue program after the do has completed
switch (answer){ // switch statement - uses answer from the keyboard to select a case
case 1:
addBook(); // adds book
break;
case 2:
for (int i=0; i<2; i++){
if (fictionArray[i] != null){
System.out.println(fictionArray[i]);}
if (nonfictionArray[i] != null){
System.out.println(nonfictionArray[i]);}}
break;
case 3:
for (int i=0; i<2; i++){
if(fictionArray[i].getTitle() != "Onloan"){
System.out.println(fictionArray[i]);}
if(nonfictionArray[i].getTitle() != "Onloan"){
System.out.println(nonfictionArray[i]);}}break;
case 4:
break;
case 5:
break;
case 6:
break;
}
}
}
static void addBook(){
loanbook [] loanArray = new loanbook[2];
String title,author;
int choice;
boolean onloan = false;
for(int x = 0; x < loanArray.length; x++){
System.out.print("Press 1 for Fiction or 2 for Non Fiction: "); // sub menu for fiction and non fiction
choice = keyboard.nextInt();
if (choice == 1){
for(int count = 0; count < fictionArray.length; count++){
System.out.print("Enter title: ");
title= keyboard.nextLine();
title= keyboard.nextLine();
System.out.print("Enter author: ");
author= keyboard.nextLine();
fictionArray[location] = new fiction(title, author, onloan);
System.out.println("The book information you entered was : " + fictionArray[count].toString()); // this will show the entry which was inout to the array
count++; }}
else if (choice == 2) {
for(int count = 0; count < nonfictionArray.length; count++){
System.out.print("Enter title: ");
title= keyboard.nextLine();
title= keyboard.nextLine();
System.out.print("Enter author: ");
author= keyboard.nextLine();
nonfictionArray[location] = new nonfiction(title, author, onloan);
System.out.println("The book information you entered was : " + nonfictionArray[count].toString()); // this will show the entry which was inout to the array
count++;}}
else{ int noBooks = loanArray.length;
for (int i=0; i<noBooks; i++){
System.out.print(loanArray[x]);
}}}} // addbook
} // Library end
Superclass
public class loanbook {
private String title,author;
static int bookID = 0;
private boolean onloan;
public loanbook(String pTitle,String pAuthor,boolean ponloan){
title = pTitle;
author = pAuthor;
onloan = ponloan;
bookID++;
} // Constructor
public void setTitle(String pTitle){
title = pTitle;
} // setTitle
protected String getTitle(){
return title;
} // getTitle
protected String getAuthor(){
return author;
} // getAuthor
public String toString(){
return " Onloan = "+onloan +"\n BookID: "+ bookID+"\n" + " Title: "+ getTitle()+"\n" +" Author : "+ getAuthor()+ "\n";
}
} // loanbook
you need to increment your location after you set something to it.