Issue with the way my program is processing input and output

[Naziru Gelajo]

Greetings everyone, I'm making a student Database utilizing an ArrayList Data Structure. The program works well for the most part except for when trying to add a student, a few things get really wonky. What I mean by wonky is that as soon as it prompts for a student ID, the program immediately follows it with a prompt for a netID and does not allow the user to input a value for both. The program also ends abruptly when prompting the student for gender. Here is the output:

Welcome to the UI Student Directory Database!
Please choose from the Choices below:
1. Add a Student
2. Remove a Student
3. Display Student Directory
4. Exit Database
---------------------------------------------
1
Please enter the first name of the Student:
Dan
Please enter the last name of the Student:
Steward
Please enter the major of the Student:
CE
Please enter the student's GPA:
3.2
Please enter the student's UIN:
Please enter the Student's netID:
876578
Please enter the Student's age:
30
Please enter the Student's gender:
---------------------------------------------
Welcome to the UI Student Directory Database!
Please choose from the Choices below:
1. Add a Student
2. Remove a Student
3. Display Student Directory
4. Exit Database
---------------------------------------------
m
Exception in thread "main" java.util.InputMismatchException
at java.util.Scanner.throwFor(Scanner.java:864)
at java.util.Scanner.next(Scanner.java:1485)
at java.util.Scanner.nextInt(Scanner.java:2117)
at java.util.Scanner.nextInt(Scanner.java:2076)
at Lab3.main(Lab3.java:25)

Here is the actual code:

import java.util.Scanner;
import java.util.ArrayList;

public class Lab3 {
	static ArrayList<Student> studentDirectory = new ArrayList<Student>();
	
	public static void main(String[] args) {
		int choice;
		Scanner input = new Scanner(System.in);
		do {
			System.out.println("---------------------------------------------");
			System.out.println("Welcome to the UI Student Directory Database!");
			System.out.println("Please choose from the Choices below:");
			System.out.println("1. Add a Student");
			System.out.println("2. Remove a Student");
			System.out.println("3. Display Student Directory");
			System.out.println("4. Exit Database");
			System.out.println("---------------------------------------------");
			choice = input.nextInt();
			switch(choice) {
				case 1:
					addStudent();
					break;
				case 2:
					removeStudent();
					break;
				case 3:
					displayStudentList();
					break;
				case 4:
					System.out.println("Thanks for using the UI Student Directory! Farewell!");
					System.exit(0);
					break;
				default: 
					System.out.println("Invalid Choice! Try again!");
					break;
			} 
		} while (choice != 4);
	}

	public static void addStudent() {
		Student newStudent = new Student();
		Scanner input = new Scanner(System.in);
		String firstName;
		String lastName;
		String major;
	    double gpa;
		String UIN;
		String netID;
		int age;
		String gender;
		if (studentDirectory.size() >= 10) {
			System.out.println("Sorry Student Directory can not have more than 10 students.");
		} else {
			int i = 0;
			System.out.println("Please enter the first name of the Student:");
			firstName = input.nextLine();
			newStudent.setFirstName(firstName);
			System.out.println("Please enter the last name of the Student:");
			lastName = input.nextLine();
			newStudent.setLastName(lastName);
			System.out.println("Please enter the major of the Student:");
			major = input.nextLine();
			newStudent.setMajor(major);
			System.out.println("Please enter the student's GPA:");
			gpa = input.nextDouble();
			newStudent.setGPA(gpa);
			System.out.println("Please enter the student's UIN:"); //Things get wonky here
			UIN = input.nextLine();
			newStudent.setUIN(UIN);
			System.out.println("Please enter the Student's netID:");
			netID = input.nextLine();
			newStudent.setNetID(netID);
			System.out.println("Please enter the Student's age:");
			age = input.nextInt();
			newStudent.setAge(age);
			System.out.println("Please enter the Student's gender:");
			gender = input.nextLine();
			newStudent.setGender(gender);
			
			studentDirectory.add(i, newStudent);
			i++;
		}
	}
	
	public static void removeStudent() {
		Student theStudent = new Student();
		if (studentDirectory.size() < 1) {
			System.out.println("There is absolutely nothing to remove!");
		} else {
			Scanner input = new Scanner(System.in);
			String UIN;
			System.out.println("Please enter the UIN (Unique Identifier) of the student to remove:");
			UIN = input.nextLine();
			theStudent.setUIN(UIN);
			
			for (int i = 0; i < studentDirectory.size(); i++) {
				if (studentDirectory.get(i).getUIN().equals(theStudent.getUIN())) {
					studentDirectory.remove(i);
				}
			}
		}
		
	}
	
	public static void displayStudentList() {
		System.out.println("First Name:" + "\t" + "Last Name:" + "\t" +
				"Major:" + "\t" + "GPA:" + "\t" + "UIN:" + "\t" +
				"NetID:" + "\t" + "Age:" + "\t" + "Gender:");
		for (Student theStudent : studentDirectory) {
			System.out.println(theStudent.getFirstName() + "\t" + theStudent.getLastName()
			+ "\t" + theStudent.getMajor() + "\t" + theStudent.getGPA() + "\t" + 
					theStudent.getUIN() + "\t" + theStudent.getNetID() + "\t" + 
					theStudent.getAge() + "\t" + theStudent.getGender());
		}
	}
	
}


class Student {
	private String firstName;
	private String lastName;
	private String major;
	private double gpa;
	private String UIN;
	private String netID;
	private int age;
	private String gender;
	
	public Student() {
		this.firstName = "";
		this.lastName = "";
		this.major = "";
		this.gpa = 0.0;
		this.UIN = "";
		this.netID = "";
		this.age = 0;
		this.gender = "";
	}
	
	public Student(String firstName, String lastName, String major, double studentGPA, String studentUIN,
			String netID, int studentAge, String studentGender) {
		
		this.firstName = firstName;
		this.lastName = lastName;
		this.major = major;
		this.gpa = studentGPA;
		this.UIN = studentUIN;
		this.netID = netID;
		this.age = studentAge;
		this.gender = studentGender;
	}

	public String getFirstName() {
		return firstName;
	}
	
	public String getLastName() {
		return lastName;
	}
	
	public String getMajor() {
		return major;
	}
	
	public double getGPA() {
		return gpa;
	}
	
	public String getUIN() {
		return UIN;
	}
	
	public String getNetID() {
		return netID;
	}
	
	public int getAge() {
		return age;
	}
	
	public String getGender() {
		return gender;
	}
	
	public void setFirstName(String firstName) {
		this.firstName = firstName;
	}
	
	public void setLastName(String lastName) {
		this.lastName = lastName;
	}
	
	public void setGPA(double gpa) {
		this.gpa = gpa;
	}
	
	public void setMajor(String major) {
		this.major = major;
	}
	
	public void setUIN(String UIN) {
		this.UIN = UIN;
	}
	
	public void setGender(String gender) {
		this.gender = gender;
	}
	
	public void setNetID(String netID) {
		this.netID = netID;
	}
	
	public void setAge(int age) {
		this.age = age;
	}
	
	public boolean equals() {
		return (this.firstName.equals(firstName) && this.lastName.equals(lastName) && this.gender.equals(gender) 
				&& this.netID.equals(netID) && this.age == age && this.UIN.equals(UIN) && this.major.equals(major)
				&& this.gpa == gpa);
	}
	
}

I don't see where I'm going wrong. I'm a bit flabbergasted. The addStudent method in the Lab3 class seems like it should work, but it behaves in a wonky fashion. Thanks!

[Naziru Gelajo]

BTW the error that says Lab3.java line 25 should actually be line 19. I removed the comments at the beginning of the program that illustrates the author and stuff.

[Tushar Goel]

the problem is with using int and then immediately after you are using nextLine.

What happening is once you enter int value and press enter than it is consider it as an input and when you try to use nextLine() then that input  Énter' is consumed and goes to another line.

See this post for more explanation.

[Naziru Gelajo]

Tushar Goel wrote:the problem is with using int and then immediately after you are using nextLine.

What happening is once you enter int value and press enter than it is consider it as an input and when you try to use nextLine() then that input  Énter' is consumed and goes to another line.

See this post for more explanation.

Excellent,

Thank you very much for that.

[Campbell Ritchie]

Why are all the members of your class static?
Why are you using multiple Scanner objects? You only need one Scanner object to read from the keyboard. That is why I wrote a utility class, which you will find out about in the older links.