Java Encapsulation and Inheritance

[Monica Vedham]

I created a code for Inheritance and Encapsulation. It throws error for two testcases and it produces answer for another two. Kindly help me.

import java.io.*;
import java.util.*;

class Account {
	public String accountNumber;
	public double amount;
	public String customerName;

	public String getAccountNumber() {
		return this.accountNumber;
	}

	public double getAmount() {
		return this.amount;
	}

	public String getCustomerName() {
		return this.customerName;
	}

	public void setAccountNumber(String newAccNum) {
		this.accountNumber = newAccNum;
	}

	public void setAmount(double newAmount) {
		this.amount = newAmount;
	}

	public void setCustomerName(String newCustomerName) {
		this.customerName = newCustomerName;
	}
}

class SavingsAccount extends Account {
	public double interestRate;

}

class FixedAccount extends Account {
	public int numberOfYears;
}

class CheckingAccount extends Account {
}

class Main {
	public static void main(String[] args) throws IOException {
		Scanner sc = new Scanner(System.in);
		Account ac = new Account();
		SavingsAccount sa = new SavingsAccount();
		FixedAccount fa = new FixedAccount();
		CheckingAccount ca = new CheckingAccount();
		System.out.println("1)Checking Account");
		System.out.println("2)Saving Account");
		System.out.println("3)Fixed Account");
		System.out.println("Enter Account Type");
		int choice = sc.nextInt();
		switch (choice) {
		case 1: {

			System.out.println("Enter The Account Number");
			ac.accountNumber = sc.next();
			System.out.println("Enter The Customer Name");
			ac.customerName = sc.next();
			System.out.println("Enter The Amount");
			ac.amount = sc.nextDouble();
			System.out.println("Hi " + ac.getCustomerName() + ", " + "currently you are using Checking Account.");
			System.out.println("Your account number is " + ac.getAccountNumber());
			System.out.println("Your are currently holding amount Rs." + ac.getAmount());
			break;
		}

		case 2: {

			System.out.println("Enter The Account Number");
			ac.accountNumber = sc.next();
			System.out.println("Enter The Customer Name");
			ac.customerName = sc.next();
			System.out.println("Enter The Amount");
			ac.amount = sc.nextDouble();
			System.out.println("Enter The InterestRate");
			sa.interestRate = sc.nextDouble();
			System.out.println("Hi " + ac.getCustomerName() + ", " + "currently you are using Savings Account.");
			System.out.println("Your account number is " + ac.getAccountNumber());
			System.out.println("Your are currently holding amount Rs." + ac.getAmount());
			System.out.println("Rate of interest is " + sa.interestRate + "%");
			break;
		}

		case 3: {

			System.out.println("Enter The Account Number");
			ac.accountNumber = sc.next();
			System.out.println("Enter The Customer Name");
			ac.customerName = sc.next();
			System.out.println("Enter The Amount");
			ac.amount = sc.nextDouble();
			System.out.println("Enter The Number Of Years");
			fa.numberOfYears = sc.nextInt();
			System.out.println("Hi " + ac.getCustomerName() + ", " + "currently you are using Fixed Account.");
			System.out.println("Your account number is " + ac.getAccountNumber());
			System.out.println("Your are currently holding amount Rs." + ac.getAmount());
			System.out.println("Number of years " + fa.numberOfYears);
			break;
		}

		default:
			System.out.println("Invalid Account Type");
		}
	}
}

The error i get is.....

Exception in thread "main" java.util.InputMismatchException
at java.util.Scanner.throwFor(Scanner.java:909)
at java.util.Scanner.next(Scanner.java:1530)
at java.util.Scanner.nextDouble(Scanner.java:2456)
at Main.main(Main.java:63)

[Ganesh Patekar]

Welcome to CodeRanch! please use code tag to post your code from next time. You can refer this, click here --->Use Code Tags to know how to post code in code tag.

Monica Vedham wrote:Exception in thread "main" java.util.InputMismatchException
at java.util.Scanner.throwFor(Scanner.java:909)
at java.util.Scanner.next(Scanner.java:1530)
at java.util.Scanner.nextDouble(Scanner.java:2456)
at Main.main(Main.java:63)

InputMismatchException error is thrown by a Scanner to indicate that the token retrieved does not match the pattern for the expected type, or that the token is out of range for the expected type.
For an example in main method of Main class you are taking input from user in form of int i.e. sc.nextInt() for choice of account type here on line no 58-59.

System.out.println("Enter Account Type");
int choice = sc.nextInt();

If you either enter value out of range of int type Or non- int value like floating point number Or String Or char where It was expecting int then It gives that error.
Can you please show us how you are entering values?

Edit:
Other changes I think you need to make are:

Don't write that much code in main method, better write a separate method getUserInput() Or something you think more descriptive. Worth reading Main Is A Pain

Following code is redunandant code on line no 63-68, 77-82 and 94-99 same code for all three types of account so you can write It once and store their values in three variables and in switch case you can use setter methods of Account class to set those values.

System.out.println("Enter The Account Number");
ac.accountNumber = sc.next();
System.out.println("Enter The Customer Name");
ac.customerName = sc.next();
System.out.println("Enter The Amount");
ac.amount = sc.nextDouble();

In following code on line no 5, 6 and 7 you can declare these variables with private access modifiers. As all of them have getter and setter method.

public String accountNumber;
public double amount;
public String customerName;

Same you you can declare below variables as private.Create getter and setter methods for them and access them using those methods.

class SavingsAccount extends Account {
    public double interestRate;
 
}
 
class FixedAccount extends Account {
    public int numberOfYears;
}

[Liutauras Vilda]

Welcome to the Ranch. There is one four things which is are out of scope of your main problem.

1. Make your instance variables private. You already have written so called setters and getters to assign or retrieve instance variables values, so use them.
2. Where is your constructor? Are you happy to open an account which doesn't belong to no one? Don't you want to let customer to open an account with certain amount of money in it?
3. How do you know that certain account number doesn't exist before you set one? Maybe such number needs to be auto increment?
4. Since you are familiar with keyword this, you can let parameter and instance variables have the same names.

[Liutauras Vilda]

Also, try not to use wild card imports (lines 1, 2). Campbell Ritchie told me once these are called on-demand imports, not wild card.

Instead, specify importing classes explicitly:

import java.io.IOException;
import java.util.Scanner;

[Dave Tolls]

            System.out.println("Enter The Customer Name");
            ac.customerName = sc.next();
            System.out.println("Enter The Amount");
            ac.amount = sc.nextDouble();

Not sure which line is line 63 that is causing the issue, but if it is around here then what name is being entered?

Can you show the output from the app (not just the stack trace)?

I ask because if the name is something like 'John Smith' then Scanner's next() method doesn't do what you expect.

[Liutauras Vilda]

Dave Tolls wrote:Not sure which line is line 63..

Dave, zoom browser up to 110%, this is what I do sometimes, when having problems like you do.

Dave Tolls wrote:...what name is being entered?

'John Smith' shouldn't cause that kind of issue. It just would make him become 'John'.

[Monica Vedham]

[Moderation comment] Removed a huge amount of unnecessary quote

The expected result is...
1)Checking Account
2)Saving Account
3)Fixed Account
Enter Account Type
Enter The Account Number
Enter The Customer Name
Enter The Amount
Enter The InterestRate
Hi Jimesh Sharma, currently you are using Saving Account.
Your account number is ACC456753
Your are currently holding amount Rs.65846.0
Rate of interest is 3.0%

[Monica Vedham]

Dave Tolls wrote:

            System.out.println("Enter The Customer Name");
            ac.customerName = sc.next();
            System.out.println("Enter The Amount");
            ac.amount = sc.nextDouble();

Not sure which line is line 63 that is causing the issue, but if it is around here then what name is being entered?

Can you show the output from the app (not just the stack trace)?

I ask because if the name is something like 'John Smith' then Scanner's next() method doesn't do what you expect.

May i know which function of Scanner can help the input like "John Smith"

[Liutauras Vilda]

Monica Vedham wrote:May i know which function of Scanner can help the input like "John Smith"

Look for the method called nextXXXX() in the Java API here.

[Dave Tolls]

Liutauras Vilda wrote:

Dave Tolls wrote:...what name is being entered?

'John Smith' shouldn't cause that kind of issue. It just would make him become 'John'.

    public static void main(String args[]) {
        Scanner sc = new Scanner(System.in);
        System.out.println("Enter name:  ");
        String name = sc.next();
        System.out.println("Enter int:  ");
        int i = sc.nextInt();
    }

Run that and enter John Smith for the name.

What happens is John is picked up as the name, and Smith is still in the buffer.
nextInt() then attempts to read an int but find only 'Smith' and throws an exception:

Enter name:  
John Smith
Enter int:  
Exception in thread "main" java.util.InputMismatchException
at java.util.Scanner.throwFor(Scanner.java:909)
at java.util.Scanner.next(Scanner.java:1530)
at java.util.Scanner.nextInt(Scanner.java:2160)
at java.util.Scanner.nextInt(Scanner.java:2119)
at stuff.TestStuff.main(TestStuff.java:22)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at com.intellij.rt.execution.application.AppMain.main(AppMain.java:144)

[Liutauras Vilda]

Dave Tolls wrote:What happens is John is picked up as the name, and Smith is still in the buffer.

Ah, oldest Scanner's trick. I didn't look into it as a sequence of steps. You're absolutely right. Have a cow.

[Ganesh Patekar]

I also didn't notice that, great job Dave  

[Dave Tolls]

Liutauras Vilda wrote:
Look for the method called nextXXXX() in the Java API here.

And then be prepared to handle leftover line feeds...
;)

[Campbell Ritchie]

The number of times I have had that Exception. . . . I have stopped looking for it in the code; I have seen it so often that I simply guess it has happened (‍). You need to beware of mixing nextLine and nextAnythingElse with a Scanner. I believe the correct solution is to create a utility class, maybe called KeyboardInputs, which you use for all your input and that class hides a Scanner from you. There is an explanation of a similar problem mixing nextInt and nextLine (and a possible solution) here. Please tell us which book you are using and what it says Scanner#nextLine does. Then compare that with what the API documentation says.

[Campbell Ritchie]

Aaaaaaaaaaaaaaaaaaaaaaaaargh! I have guessed wrong!

No, it is a different error from what I thought. If you want a name after an int, try

System.out.print("Please enter number and push enter key: ");
i = myScanner.nextInt();
myScanner.nextLine(); // needed to remove zero-length String from buffer
System.out.print("Please enter name and push enter key: ");
name = myScanner.nextLine();