java error - how to solve the \n in the buffer (if that is the cause of the error)

Question

The following is my code. The code works fine with the 'save' and 'search' menus. However, after I 'delete' a person and select the next menu as 'search', the program skips the part where the user enters a name, thus showing "no results found" as the result.

I thought that the \\n may be the problem and tried parseInt(), System.out.flush(), and using nextLine() as written in the comments in the code but they all seemed not to work.

Also, I am confused why in some cases, even though there is a \\n left in the buffer, I can enter the 'name' without the program skipping.

Please let me know if the \\n is not the cause of the problem. Thank you for your time.

import java.util.Scanner;

class PhoneInfo
{
    String name;
    private String phoneNumber;
    private String birthDay;
    private String birthYear;
    private int choice;

    public PhoneInfo(String name, String phoneNumber, String birthDay)
    {
        this.name = name;
        this.phoneNumber = phoneNumber;
        this.birthDay = birthDay;
    }

    public PhoneInfo(String name, String phoneNumber, String birthDay, String birthYear)
    {
        this(name, phoneNumber, birthDay);
        this.birthYear = birthYear;
    }

    public void showPhoneInfo()
    {
        System.out.println("name: " + name);
        System.out.println("phone no.: " + phoneNumber);
        System.out.println("birthday: " + birthDay);
        if(birthYear == null)
            System.out.println("birth year: no record");
        else
            System.out.println("birth year: " + birthYear);

        System.out.println("-----------------------------");
    }
} 

class Manager //save, search, delete data
{
    PhoneInfo[] pBook = new PhoneInfo[100];
    Scanner input = new Scanner(System.in);

    public PhoneInfo inputData()
    {   
        System.out.print("name: ");
        String name = input.nextLine();

        System.out.print("phone no.: ");
        String phoneNumber = input.nextLine();

        System.out.print("birthday: ");
        String birthDay = input.nextLine();

        System.out.print("birth year: ");
        String birthYear = input.nextLine();

        PhoneInfo pData = new PhoneInfo(name, phoneNumber, birthDay, birthYear);

        System.out.println("-----------------------------");

        return pData;
    }

    public void saveData()
    {   
        for(int i=0; i<100; i++)
        {
            if(pBook[i] == null)
            {   
                pBook[i] = inputData(); //new entry
                break;
            }
            else
            {
                if(i == 99)
                    System.out.println("database full");
                else
                    continue;
            }
        }
    }

    public void searchData()
    {
        System.out.print("name: ");
        //tried putting System.out.flush(); here as well... didn't work
        String name = input.nextLine(); // do not want to use input.next() if possible
        System.out.println("\nSearching data...\n");
        for(int i=0; i<100; i++)
        {
            if(pBook[i] != null)
            {
                if(pBook[i].name.equals(name))
                {
                    pBook[i].showPhoneInfo();
                        break;
                }
                else
                    continue;
            }
            else
            {
                System.out.println("no results found");
                break;
            }
        }
    }

    public void deleteData()
    {
        int idx;
        System.out.print("name: ");
        String name = input.nextLine();

        idx = getIndex(name);
        if(idx == -1)
            System.out.println("no matching name");

        System.out.println("Are you sure you want to delete " + name + "?");
        System.out.print("1. yes\n2. no\n> ");
        int choice = input.nextInt();
        if(choice == 1)
        {   
            for(int i=idx; i<99; i++)
                pBook[i] = pBook[i+1];
            System.out.println(name + " deleted...");
            System.out.println("-----------------------------");
        }
        if(choice == 2)
            return;
    }

    public int getIndex(String name)
    {
        int index = -1;
        for(int i=0; i<100; i++)
        {   
            if(pBook[i] != null)        
                if(pBook[i].name.equals(name)) //error --> worked when I added if(pBook[i] != null). why?? what difference did it make?
                    index = i;
                else
                    continue;
            else
                continue;
        }
        return index;
    }
}

class PhoneBookVer3
{
    static Scanner input = new Scanner(System.in);

    public static void showMenu()
    {
        System.out.println("[MENU]");
        System.out.println("choose...");
        System.out.println("1. save data");
        System.out.println("2. search data");
        System.out.println("3. delete data");
        System.out.println("4. exit program");
        System.out.print("> ");
    }

    public static void main(String[] args)
    {
        PhoneBookVer3 pb = new PhoneBookVer3();
        int choice;
        Manager mng = new Manager();
        while(true)
        {
            pb.showMenu();
            //choice = Integer.parseInt(input.nextLine()); // why this doesn't work either..
            choice = input.nextInt();
            //input.nextLine(); //why this doensn't consume the \n???

            switch(choice)
            {
                case 1:
                    System.out.println("-----------------------------");
                    mng.saveData();
                    break;
                case 2:
                    System.out.println("-----------------------------");
                    mng.searchData();
                    break;
                case 3:
                    System.out.println("-----------------------------");
                    mng.deleteData();
                    break;
                case 4:
                    System.out.println("-----------------------------");
                    System.out.println("end of program");
                    return;
            }
        }
    }
}

Answer 1

In your method public void deleteData() , you need to do:

int choice = input.nextInt();   
input.nextLine();

The last nextLine() will consume the \\n that nexInt() is leaving.

Maybe it will be better that you use parseLine() more often and convert String to int when necessary.

Answer 2

The problem is that you are reading choice using the input.nextInt() . When you do that nextInt() will only read the integer and the newline character you enter will be read by the next nextLine() so to prevent this you can add a dummy input.nextLine() after the input.nextInt()

Code

System.out.println("Are you sure you want to delete " + name + "?");
System.out.print("1. yes\n2. no\n> ");
int choice = input.nextInt();
input.nextLine(); // to read the newline character 

Alternate method

Another method is to read the choice using nextLine() itself and then convert the input to int .

int choice = Integer.parseInt(input.nextLine());