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How to give each student a unique ID after being created by the user on JAVA program

I am working on a school project that basically allows the user to create, edit or view students. Once a student is created, they each get assigned a unique ID like 1, 2, 3, etc. All the functionally of creation, editing and displaying is working but I am stuck on have to give them a unique ID after created. Here is the code I have and in the // commented areas is what I attempted to do but I am not sure if its right. Any ideas will be very appreciated.
import java.util.Scanner;
import java.io.*;
public class MidTermProject {
public static void main(String[] args) throws IOException {
Scanner keyboard = new Scanner(System.in);
System.out.println("Here is the sample of menu choices for Main Menu.");
System.out.println("\nWelcome to University Enrollment" + "\n1. Create Student" + "\n2. Edit Student" + "\n3. Display Student" + "\n0. --- Quit ---");
System.out.println("Please enter a valid choice(1-10, 0 to Quit) :");
int userInput = keyboard.nextInt();
if(userInput == 1) {
CreateStudent();
} else if(userInput == 2) {
EdithStudent();
} else if(userInput == 3) {
DisplayStudent();
} else if(userInput == 0) {
System.out.print("Done");
} else {
System.out.println("Invalid Option, Please try again.");
userInput = keyboard.nextInt();
if(userInput == 1) {
CreateStudent();
} else if(userInput == 2) {
EditStudent();
} else if(userInput == 3) {
DisplayStudent();
} else if(userInput == 0) {
System.out.print("Done");
}
}
}
public static void CreateStudent() throws IOException {
String FullName;
String address;
String city;
String state;
int StudentID;
Scanner keyboard = new Scanner(System.in);
FileOutputStream fstream =
new FileOutputStream("StudentInfo.dat");
DataOutputStream outputFile =
new DataOutputStream(fstream);
System.out.print("\nPlease enter your information bellow.\n" + "\nFull Name: ");
FullName = keyboard.nextLine();
outputFile.writeUTF(FullName);
System.out.print("Address: ");
address = keyboard.nextLine();
outputFile.writeUTF(address);
System.out.print("City: ");
city = keyboard.nextLine();
outputFile.writeUTF(city);
System.out.print("State: ");
state = keyboard.nextLine();
outputFile.writeUTF(state);
//allowed the user to select their own ID number
System.out.print("Please get a Student ID(1-10): ");
//Store the selected number on StudentID
StudentID = keyboard.nextInt();
//The for loop will increment index each time a user is created
for(int index = 0; index == StudentID; index++) {
//The if statement will compare index and StudentID, if equal will ask the user to enter a different number
if(index == StudentID) {
System.out.print("The selected ID has been selected already, Please select a different ID");
StudentID = keyboard.nextInt();
}
}
//write the number in the file
outputFile.writeInt(StudentID);
System.out.print("Successfully Created");
}
public static void EditStudent() throws IOException {
String editName;
String editaddress;
String editCity;
String editState;
Scanner keyboard = new Scanner(System.in);
RandomAccessFile file =
new RandomAccessFile("StudentInfo.dat", "rw");
file.seek(0);
System.out.print("\nPlease enter NEW information bellow.\n" + "\nFull Name: ");
editName = keyboard.nextLine();
file.writeUTF(editName);
System.out.print("Address: ");
editaddress = keyboard.nextLine();
file.writeUTF(editaddress);
System.out.print("City: ");
editCity = keyboard.nextLine();
file.writeUTF(editCity);
System.out.print("State: ");
editState = keyboard.nextLine();
file.writeUTF(editState);
file.close();
System.out.print("Successfully Edited");
}
public static void DisplayStudent() throws IOException {
FileInputStream fstream = new FileInputStream("StudentInfo.dat");
DataInputStream inputFile = new DataInputStream(fstream);
String student;
boolean endOfFile = false;
while(!endOfFile)
{
try
{
student = inputFile.readUTF();
System.out.print(student + " ");
}
catch (EOFException e)
{
endOfFile = true;
}
}
System.out.println("\nDone");
inputFile.close();
}

Firstly, following Java naming conventions makes your code more readable. So use lowercase first when naming a variable: studentId rather than StudentId. Initial-caps is for class names.
In your create student method, your for loop makes no sense.
for(int index = 0; index == StudentID; index++) {
//The if statement will compare index and StudentID, if equal will ask the user to enter a different number
if(index == StudentID) {
System.out.print("The selected ID has been selected already, Please select a different ID");
StudentID = keyboard.nextInt();
}
}
A for loop simply increments the index defined in the first clause, stepping the increment according to the third clause, until the second clause proves true.
So in your code, if the user enters 4, your loop counts 0, 1, 2, 3, 4 «bingo». Now that we reached the user’s specified number, we go on to ask them for another number. And we’re done. But that process is illogical.
That code fails to accomplish your goal of checking for existing students. You need to review all existing students one-by-one. Compare each existing student ID against the desired ID. Only after exhausting the list of all known students should we use the desired ID. If we find a match on an existing student, then we break out of the loop to ask the user for another choice of ID. And we need another outer loop to continue this “ask, search, ask again if needed” process until an unused desired ID is determined.
Big tip: If you write out your problem statement and solution attempt as plain prose, similar to what I just did in the paragraph above, your programming will go more smoothly. And your written prose will be fodder for writing helpful comments in your source code.

Accepting string inputs into an array and checking the availability of the string in the array

So I am completely new to java, and I want to create a code to accept string inputs from a user, and store it into an array. After this in the next statement, I will type a value into the terminal, and I want the code to compare my string input to one of the strings in the array and print available on the terminal when the string is available and vice versa. The first part of my code was right (hopefully) but I had a problem in comparing the strings. I feel it doesn't check the strings with my input in the code. Here is my code, Could anyone please help me with this? Thank you so much.
import java.util.Scanner;
class Course {
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
String a[] = new String[20] //assuming max 20 strings
System.out.println("Enter no. of courses");
int no_of_courses = sc.nextInt(); // number of strings
if (no_of_courses <= 0)
System.out.println("Invalid Range");
else {
System.out.println("Enter course names:");
for (int i = 0; i < no_of_courses; i++) {
a[i] = sc.next(); //accepting string inputs
}
System.out.println("Enter the course to be searched:");
String search = sc.next() //entering a string to search
for (int i = 0; i < no_of_courses; i++) {
if (a[i].equals(search)) //I feel the problem is here
System.out.println(search + "course is available");
break;
else
System.out.println(search + "course is not available");
}
}
}
}
I expect the output to be
<string> course is available
when my string matches a string in the array and
<string> course is not available
when my entered string doesn't match a string in the array
But there is no output :(

I have modified your code and commented on line where it need to be explained. check it carefully.
import java.util.Scanner;
class Course {
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
System.out.println("Enter no. of courses");
int no_of_courses = sc.nextInt(); // number of strings
String a[] = new String[no_of_courses]; // do not assume when you have proper data.
if (no_of_courses <= 0)
System.out.println("Invalid Range");
else {
System.out.println("Enter course names:");
for (int i = 0; i < no_of_courses; i++) {
a[i] = sc.next(); // accepting string inputs
}
System.out.println("Enter the course to be searched:");
String search = sc.next(); // entering a string to search
boolean flag = false;
for (int i = 0; i < no_of_courses; i++) {
if (a[i].equals(search)) // I feel the problem is here
{
flag = true;//do not print here. just decide whether course is available or not
break;
}
}
//at the end of for loop check your flag and print accordingly.
if(flag) {
System.out.println(search + "course is available");
}else {
System.out.println(search + "course is not available");
}
}
}
}

class Course {
public static void main(String[] args)
{
Scanner sc = new Scanner(System.in);
String a[] = new String[20] ; //assuming max 20 strings
System.out.println("Enter no. of courses");
int no_of_courses = sc.nextInt(); // number of strings
if(no_of_courses <= 0)
System.out.println("Invalid Range");
else
{
System.out.println("Enter course names:");
for(int i=0 ; i < no_of_courses ; i++)
{
a[i] = sc.next(); //accepting string inputs
}
System.out.println("Enter the course to be searched:");
String search = sc.next() ; //entering a string to search
boolean found = false;
for(int i = 0 ; i < no_of_courses ; i++)
{
if(a[i].equalsIgnoreCase(search)) //I feel the problem is here
{
**found = true;**
break;
}
}
if(found) {
System.out.println(search+ "course is available");
}else {
System.out.println(search+ "course is not available");
}
}
}
}

This is really a good effort and you almost got it. So just a couple of things
Since you are inputting the number of courses, just use that value to initialise your array (it's just a good practice to get into to try not initialise things before you actually need them).
If you are doing String comparisons and case sensitivity does not matter, rather use .equalsIgnoreCase(String)
To solve your problem, you just needed a boolean variable to indicate whether or not you had found a match. Initially this would be FALSE (no match found) and you would run through your array until a match is found. Once found this would be flagged TRUE and you'd breakout your loop (which you correctly did).
Only once out your loop, you'd print out whether you found a match.
Have a look:
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
System.out.println("Enter no. of courses");
int no_of_courses = sc.nextInt(); // number of strings
if (no_of_courses <= 0) {
System.out.println("Invalid Range");
} else {
String a[] = new String[no_of_courses];
System.out.println("Enter course names:");
for (int i = 0; i < a.length; i++) {
a[i] = sc.next(); //accepting string inputs
}
System.out.println("Enter the course to be searched:");
String search = sc.next(); //entering a string to search
boolean courseFound = Boolean.FALSE;
for(int i = 0; i < a.length; i++) {
if (a[i].equalsIgnoreCase(search)) {
courseFound = Boolean.TRUE;
break;
}
}
if(courseFound) {
System.out.println(search + "course is available");
} else {
System.out.println(search + " course is not available");
}
}
}
Oh, just for interest (and when you start working with some more advanced constructs), you could always just use stream, which was introduced in Java 8. It'll trim down 12 lines to 5...
if(Arrays.stream(a).anyMatch(i -> i.equalsIgnoreCase(search))) {
System.out.println(search + " course is available");
} else {
System.out.println(search + " course is not available");
}

I noticed a few things - Does your program run to the end? When i copy/pasted into my ide i noticed a few missing semi-colons, and like Yhlas said, your last if/else statement syntax is incorrect.
And this doesn't have anything to do with whether or not your program will give you the right answer, but your last loop will print over and over again because it will check each element in a, and each time it loops and finds a mismatch it will print something out

Is there any way to pass a mutator method as an argument to another method?

I'm creating a text based game, I have a class made for the main character so you can set the characters name, etc. What I'm trying to figure out is, is there any way to pass a mutator (character.setname(input)) as an argument to another method. When I try to do it I'm told that I can't use a void type as an argument to a method. When I was writing out the code for the user to enter their name, and everything else it was repetitive with the error checking so I wanted to create my own method I could call that would error check for me. A couple sentences use the setname method to reset the name if it was entered incorrectly but I can't directly use setname in the error checking method because it's going to be using the same method to check other inputs of data.
Is there any way around this?
Here is the code as requested: I indeed may be overcomplicating the problem, I'm pretty new to java so I'm still learning.
The following code is the code I use to check if the user entered something correctly, it accepts an array which contains all the possible correct answers the user can type in, I've tried to design it in a way that I can error check anything with it, not just "yes" or "no" statements, getVariable is the accessor method, and setVariable is the one I'm trying to get to work, I'm trying to pass the mutator as well so I can reset the error
public void confirmEntry(String question, String[] options, String getVariable, setVariable) throws InterruptedException
{
boolean correctEntry = false;
System.out.print("Is this correct? ");
for(int i = 0; i < options.length - 1; i++)
{
System.out.print(options[i] + ", ");
}
System.out.print("or ");
System.out.print(options[options.length - 1] + ": ");
input = in.nextLine();
for(int i = 0; i < options.length; i++)
{
if(input.equals(options[i]))
{
correctEntry = true;
System.out.println(correctEntry);
}
}
System.out.println(correctEntry);
while(correctEntry == false)
{
Thread.sleep(2000);
System.out.print("You must enter ");
for(int i = 0; i < options.length - 1; i++)
{
System.out.print("\"" + options[i] + "\", ");
}
System.out.print("or ");
System.out.print("\"" + options[options.length - 1] + "\" to continue: ");
Thread.sleep(2000);
System.out.println();
System.out.println("You chose " + getVariable);
Thread.sleep(2000);
System.out.print("Is this correct? ");
for(int i = 0; i < options.length - 1; i++)
{
System.out.print(options[i] + ", ");
}
System.out.print(" or ");
System.out.print(options[options.length - 1] + ": ");
input = in.nextLine();
for(int i = 0; i < options.length; i++)
{
if(input.equals(options[i]))
{
correctEntry = true;
}
}
}
}
The following code is what is currently in the method where you enter information about the character. I'm trying to move more of the code into the error checking method so that each time I ask the user a question, name, age, etc. I just simply need to call the method.
public void characterCreation() throws Exception
{
//create an instance of the class player (your character creation)
Player character = new Player();
//Initial Introduction to the game
System.out.println("Welcome to Stranded!");
Thread.sleep(2000);
System.out.println("Tell us a little about yourself!");
Thread.sleep(2000);
//______________________________________________________________________________________________________________
//SET YOUR CHARACTER'S NAME
String[] yesNo = {"yes", "no"}; //array to feed into confirmEntry method
System.out.print("Enter your character's name: ");
input = in.nextLine(); //asks for input of the name
character.setName(input); //sets name in the player class
System.out.println("You chose " + character.getName()
+ " for your character's name");
Thread.sleep(2000);
confirmEntry("Enter your character's name: ", yesNo, character.getName(), character.setName(input));
while(input.equals("no"))
{
Thread.sleep(2000);
System.out.print("Enter your character's name: "); //prompt to enter name again
input = in.nextLine();
character.setName(input); //sets name in player class
Thread.sleep(2000);
System.out.println("You chose " + character.getName()
+ " for your character's name"); //confirms what user entered for name
Thread.sleep(2000);
confirmEntry("Enter your character's name: ", yesNo, character.getName(), character.setName(input));
}
I'm trying to move more code after the SET CHARACTER NAME comment into the confirmEntry method, however the rest of the code involved with the character's name uses the mutator to set the name. That's the problem. I wanted to try to get as much code into confirmEntry as possible so whenever I ask the user to enter something about their character I basically just have to call the method.

If you are using java 8 you can create your method with a method reference param :
public void functionName(Consumer<String> setter){setter.
accept(string);}
and to call your method you can use : functionName(character::setname);
you can see : http://www.informit.com/articles/article.aspx?p=2171751&seqNum=3

What is an entry? It appears to be some value that the user has entered.
class Entry{
String value;
public Entry(String value){
this.value = value;
}
public boolean confirm(String input){
return value.equals(input);
}
}
How about you store all of your entries.
Map<String, Entry> entries = new HashMap<>();
String message = "Enter your character's name: ";
System.out.println(message);
String input = in.nextLine();
entries.put(message, new Entry(input));
Now when you want to confirm.
public void confirmEntries(){
for(String message: entries.keySet()){
System.out.println(message);
System.out.println(entries.get(message) + "yes/no?");
//get some input and update the value. etc.
}
}
Another way to do it would be to create a Runnables.
List<Runnable> entryRunnables = new ArrayList<>();
Then anytime you want to add an action.
Runnable r = ()->{
System.out.println("Enter your players name, yes/no");
String input = in.readLine();
//check input and do stuff.
}
entryRunnables.add(r);
Now to check entries. (stream method)
entryRunnables.forEach(Runnable::run);
Or
for(Runnable r: entryRunnables){
r.run();
}

for loop - looping more than its supposed to?

public static void choice( String arrayString[], double arrayReal[])
{
int choice;
Scanner sc = new Scanner(System.in);
System.out.println("1.display mark");
System.out.println("2.exit");
choice = sc.nextInt();
while (choice !=2 && choice != 1)
{
System.out.println("invalid input enter again");
choice = sc.nextInt();
}
switch (choice)
{
case 1:
output(arrayString, arrayReal);
break;
case 2:
System.out.println("exiting");
break;
default:
System.out.println("invalid choice choose between 1 and 2");
choice = sc.nextInt();
}
}
public static void output(String arrayString[], double arrayReal[])
{
String name;
Scanner sc = new Scanner(System.in);
for (int i=0;i<arrayString.length;i++)
{
System.out.println(arrayString[i]);
}
System.out.println("enter stident name");
name = sc.nextLine();
for (int k=0;k<arrayString.length;k++)
{
if(!arrayString.equals(name))
{
System.out.println("invalid name");
choice(arrayString, arrayReal);
}
}
for (int j=0;j<arrayString.length;j++)
{
if (arrayString[j].equals(name))
{
System.out.println("mark of " + arrayString[j] + "is " + arrayReal[j]);
}
}
im trying to validate the student name and if it doesnt equal to any of the names in the array return back to the menu. it does go back to the menu but the problem is after going back to the menu even if i type the correct student name if keps going back to the menu. i thought for loops were supposed to loop set amount of times and pass to the next code?? is that right? also is my approach correct? ive tried putting if else in the last for loop but that didnt end up as i wanted it to as well. any help is appreciated thanks!
EDIT-
thanks for spotting the mistake. fixed !arrayString.equals(name) to !arrayString[k].equals(name) but still the same problem

Your problem ist here:
for (int k=0;k<arrayString.length;k++)
{
if(!arrayString.equals(name))
{
System.out.println("invalid name");
choice(arrayString, arrayReal);
}
}
You are comparing an Array String[] arrayString with a String name. They are never going to be treated as equal and therefor your choice method is allways called.
Also the whole loop is totally pointless as you never use your loop index k for anything.
You don't need a loop here at all. Instead you can simply convert the String array to a temporary list and check if it contains your input:
if(!Arrays.asList(arrayString).contains(name))
{
System.out.println("invalid name");
choice(arrayString, arrayReal);
}
Edit:
here a short main Method that can be used for testing:
public static void main(final String[] args) {
final String[] test = { "Mark", "Peter" };
final double[] test2 = { 1, 2 };
choice(test, test2);
}
Input/Output:
OUTPUT: 1.display mark
OUTPUT:2.exit
INPUT: 1
OUTPUT: Mark
OUTPUT: Peter
OUTPUT: enter stident name
INPUT: Mark
OUTPUT: mark of Markis 1.0

The logic at this part, after adding the index, is still wrong:
for (int k=0;k<arrayString.length;k++)
{
if(!arrayString[k].equals(name))
{
System.out.println("invalid name");
...
}
}
this will print "invalid name" for every name in the list that is not the given name. Example: if the first name in the array does not match, you will get a message (and choice called), no matter if the second entry matches.
One way is to search the whole array until you find the name and then act on the result:
boolean found = false;
for (int k=0;k<arrayString.length;k++)
{
if(arrayString[k].equals(name))
{
found = true;
break; // stop searching
}
}
if (!found)
{
System.out.println("invalid name");
choice(arrayString, arrayReal);
}

How to get the user to input data until they enter quit then the system displays all the inputted data

Does anybody know why there in an error with this piece of code?
for ( int i=0; i<99; i++)
{
Scanner scan = new Scanner(System.in);
System.out.print ("Please Enter Game Name: Achievement Score: Minutes Played ");
Input1=scan.nextLine();
if (Input1.compareTo("quit"))
break;

compareTo() is used to compare numbers.
To compare text, you want to use equals().
e.g.
if (Input1.equals("quit"))

Use .equals() to compare the two strings. If you would like to compare the two strings regardless of the case you could use .equalsIgnoreCase(). The code below will take in values and store them in an ArrayList, when the user types quit the results that are stored in the ArrayList are presented to the user.
Scanner scan = new Scanner(System.in);
String input;
ArrayList<String> inputValues = new ArrayList<String>();
for (int i = 0; i < 99; i++) {
System.out.print("Please Enter Game Name... ");
input = scan.nextLine();
if(input.equals("quit")) {
if(inputValues.size() == 0) {
System.out.println("\nNo values have been entered");
} else {
System.out.println("\n******* Inputted Data *******");
for (String anInputText : inputValues) {
System.out.println("Game Name " + anInputText);
}
}
break;
} else {
inputValues.add(input);
}
}
}