Why am I getting Input mismatch exception error continously

Question

import java.util.*;
import java.lang.*;
import java.io.*;
class Main
{
    public static void main (String[] args)
    {
        Scanner sc=new Scanner(System.in);
        Servicecentre[] ab=new Servicecentre[4];
        String n,b;
        double c;
        boolean o;
        System.out.println("enter the details");
        for(int i=0;i<4;i++)
        {
            n=sc.nextLine();
            b=sc.nextLine();
            c=sc.nextDouble();
            sc.nextLine();
            o=sc.nextBoolean();
            ab[i]=new Servicecentre(n,b,c,o);
        }
        double ans1=findavg(ab);
        if(ans1==0)
        {
            System.out.println("No online service available");
        }
        else
        {
            System.out.format("%.1f",ans1);
        }
    }
    public static double findavg(Servicecentre[] ab)
    {
        double s=0;
        double c=0;
        for(int i=0;i<ab.length;i++)
        {
            if(ab[i].getonline())
            {
                s=s+ab[i].getcharge();
                c=c+1;
            }
        }
        if(c==0)
            return 0;
        else
            return s/c;
    }
}

class Servicecentre
{
    String name;
    String branch;
    double charge;
    boolean online;
    Servicecentre(String name, String branch,double charge,boolean online)
    {
        this.name=name;
        this.branch=branch;
        this.charge=charge;
        this.online=online;
    }
    String getname()
    {
        return name;
    }
    String getbranch()
    {
        return branch;
    }
    double getcharge()
    {
        return charge;
    }
    boolean getonline()
    {
        return online;
    }
}

This is the code of my program. I am asked to get input of following types

• Name – String
• branch – String
• Charge – double
• Online – boolean.

and I am asked to find average of the charge only when online is true.the below are their inputs.

• TVS
• Cochin
• 2000
• false
• Bajaj
• Chennai
• 1500
• true
• TCH
• TVM
• 1000
• false
• Arrow
• Chennai
• 2500
• true

I am repeatedly getting error on that bold line and I don't know what I have done wrong .the error is like

"Exception in thread "main" java.util.InputMismatchException at java.base/java.util.Scanner.throwFor(Scanner.java:939)
at java.base/java.util.Scanner.next(Scanner.java:1594)
at java.base/java.util.Scanner.nextDouble(Scanner.java:2564)
at HelloCodiva.main(Main.java:19)"

Kindly help me with the code. I am new to java.

Answer 1

Generally you get a java.util.InputMismatchException when you accidentally feed the wrong input. Validate your input before using it, and you won't receive this error.

Ex.

    Scanner sc = new Scanner(System.in);
    int number;
    System.out.println("Please enter a number:");
    while (!sc.hasNextInt()) {
        System.out.println("That's not a number!");
        sc.next(); // this is important as it clears the input buffer
    }
    number = sc.nextInt(); // finally recieve that input