Problem Using PrintWriter class !

[Muzafar Ali]

Hey guys,
i am using File class with PrintWriter class,
when i declare File class object it works wel but when i am creating the PrintWriter class object it show me error message (UnHandled Exception Type FileNotFoundException) what should i do here is the program please correct it and give me working version.

Thanks,
Muzafar

import java.io.*;
import java.util.Scanner;
//student class
class Student {
	public int studentId;
	public String firstName;
	public String lastName;
	public double GPA;
}
//central class
public class Central {
	public static Student register(){
		Student kid = new Student();
		Scanner scnr = new Scanner(System.in);
		
		System.out.println("ENTER INFORMATION ABOUT STUDENT");
		System.out.print("STUDENT ID: ");
		kid.studentId = scnr.nextInt();
		
		System.out.print("FIRST NAME: ");
		kid.firstName = scnr.next();
		
		System.out.print("LAST NAME: ");
		kid.lastName = scnr.next();
		
		System.out.println("GRADE POINT AVERAGE: ");
		kid.GPA=scnr.nextDouble();
		
		return kid;
	}
	
	public static void save(Student pupil)
	{
		String fileName = "";
		Scanner scnr = new Scanner(System.in);
		System.out.print("ENTER THE FILE NAME: ");
		fileName = scnr.next();
		
		//make sure the user entered a valid file name
		if(!fileName.equals("")){
			//indicate that you are planning to use a file
			File fileExample = new File(fileName);
			//create that file and prepare to write some values in it
			PrintWriter wrtStudent = new PrintWriter(fileExample);
			
			wrtStudent.println(pupil.studentId);
			wrtStudent.println(pupil.firstName);
			wrtStudent.println(pupil.lastName);
			wrtStudent.println(pupil.GPA);
			
			//after using the PrintWriter object, de-allocated its memory.
			wrtStudent.close();
			//let the user know that file is created.
			System.out.println("THE FILE HAS BEEN CREATED.");
		}
	}
	
	public static void show(Student std){
		System.out.println("STUDENT RECORD");
		System.out.println("STUDENT ID: "+std.studentId);
		System.out.println("FIRST NAME: "+std.firstName);
		System.out.println("LAST NAME: "+std.lastName);
		System.out.println("GRADE POINT AVERAGE: "+std.GPA);
	}
	
	public static void main(String[] args){
		String answer = "n";
		Student std = register();
		Scanner scnr = new Scanner(System.in);
		
		System.out.print("DO YOU WANT TO SAVE THIS INFORMATION (y/n)? ");
		answer = scnr.next();
		
		if( (answer.equals("y")) || (answer.equals("Y") )){
			show(std);
			save(std);
		}
	}

}

[Muzafar Ali]

Hey,

I solved it myself.
One question when i Declared all the methods simple Without using Throws Exception it shows me error but when i used Throws Exception along with method then it works but why ? can any one explain it for me?



Thanks,
Muzafar

[Fred Hamilton]

In addition to having the method throw the exception as you have done here, you should also learn about the try/catch method of handling exceptions.

Anyways, in this case it's all about how the program is supposed to react if the filename you specify in the program doesn't actually exist. You have to tell the program how to react to that situation.

probably you would benefit from some study of the concept of exception handling in java, you will encounter it a lot.

The Java Tutorial does a pretty good job, but there's plenty of other sources too.

http://java.sun.com/docs/books/tutorial/essential/exceptions/index.html

[Muzafar Ali]

Fred Hamilton wrote:In addition to having the method throw the exception as you have done here, you should also learn about the try/catch method of handling exceptions.

Anyways, in this case it's all about how the program is supposed to react if the filename you specify in the program doesn't actually exist. You have to tell the program how to react to that situation.

probably you would benefit from some study of the concept of exception handling in java, you will encounter it a lot.

The Java Tutorial does a pretty good job, but there's plenty of other sources too.

http://java.sun.com/docs/books/tutorial/essential/exceptions/index.html

Yep you are right,
I will study on them,
Another question,
Look at this program.

import java.util.Scanner;

public class Jani
{
	public static void main (String[] args)
	{
		Scanner input = new Scanner(System.in);
	
		String name1, name2;
		int rollNo1, rollNo2;
		
		System.out.print("ENTER ROLL NO 1: ");
		rollNo1=input.nextInt();
		
		System.out.print("ENTER NAME1: ");
		name1=input.nextLine();
		
		System.out.print("ENTER NAME2: ");
		name2=input.nextLine();
		
		System.out.println("NAME 1 IS: "+name1+"\nNAME 2 IS: "+name2);
	}
}

Out put is

ENTER ROLL NO 1: 12
ENTER NAME1: ENTER NAME2: myName
NAME 1 IS:
NAME 2 IS: myName

any idea why it is behaving like that, i mean why it combines two statements together and is getting only one input!
(ENTER NAME1: ENTER NAME2:) instead of this it has to show like this
ENTER NAME1:name1
ENTER NAME2:name2

if i am writing statement like this it works but not exceptiong spaces
name1=input.next();
name2=input.next();

is it possible to accept spaces and get inputs?

[Campbell Ritchie]

Please read the documentation for Scanner, find out what a "delimiter" is, what it uses as default delimiter, and also find out what happens when you push the enter key.
You may occasionally have to call the Scanner#next() method and discard the next token so as to keep your input Scanner and keyboard in step with each other.

[Muzafar Ali]

Campbell Ritchie wrote:Please read the documentation for Scanner, find out what a "delimiter" is, what it uses as default delimiter, and also find out what happens when you push the enter key.
You may occasionally have to call the Scanner#next() method and discard the next token so as to keep your input Scanner and keyboard in step with each other.

Thank you sir,
Sorry but can you modify my program and use delimiter in it ??

Thanks,
Muzafar

[Campbell Ritchie]

It does nobody any good to have a direct alteration to their code; they don't learn anything like that.

When you read the API documentation, what did you not understand? Then we can explain it for you.

[Muzafar Ali]

Campbell Ritchie wrote:It does nobody any good to have a direct alteration to their code; they don't learn anything like that.

When you read the API documentation, what did you not understand? Then we can explain it for you.

Sorry sir i will Learn from documentation myself .

Thanks,
Muzafar