Thread: java file handling

Hi all, I have a problem with a java program writing to files. I can get the main class and tester programs running (poorly) but I'm stuck trying to write user id no and 3 grade marks each to a seperate file,
this file is then supposed to be able to calculate the average for each id. I then have to sort each user into 2 other files by gender.
Could anyone have a look at my code so far and give me a few pointers where to go next. I have pieces of code that might do this but no idea where to put it to get results

Here is my code so far///////////
 import java.io.*;
 import java.io.PrintWriter; 
 public class Student
 {
   private String Lno ;//studentID;
	private String FName;//first name
	private String MiddleN;//middle name
	private String LastN;//lastname
	private double Mark1;
	private double Mark2;
	private double Mark3;
	private String gender;
 
	private String name;                 // to get Student's name./might need it yet
   public double test1, test2, test3;   // Grades on three tests.
 
           Student(String theName) {
                // Constructor for Student objects;
                // provides a name for the Student.
              name = theName;
           }
 
           public String getName() {
                // Accessor method for reading value of private
                // instance variable, name.
              return name;
           }
 
           public double getAverage() { 
                // Compute average test grade.
              return (Mark1 + Mark2 + Mark3) / 3;
           }
 
 
	//Default Constructor
	// public Student()
//    {
// 	}
	public Student()
	 {
	   Lno = "Lxxxxxxx";// studentID
		FName = "";
		MiddleN = "";
		LastN = "";
		Mark1 = 0.0;
		Mark2 = 0.0;
		Mark3 = 0.0;      
		gender = "";
	}
 
	//Set Name
	public void setNames(String name) throws IOException
 
	 {
		String[] nameSplit = name.split(" ");
		FName = nameSplit[0];
		LastN = nameSplit[nameSplit.length - 1];
		if (nameSplit[1] != LastN)
		 {
			MiddleN = nameSplit[1];
		}
	}
 
	//Set studentID 
	public void setLno(String id)throws Exception//student id L number
	 {
		//Check that characters are integers (8 total)
		int numbers = 0;
		for(int i=1; i<9; i++)//start at 1, leave the first one(0) for "L"
		 {
			if (Character.isDigit(id.charAt(i)))//put numbers from 1 to 8, check character is a digit
 
				numbers++;
		 }
// 		for(int i=5; i<9; i++)//numers from 5 to 8
// 		 {
// 			if (Character.isDigit(id.charAt(i)))//				numbers++;
// 		}
		//Check that 9 char long, and contains all numbers
		//char hyphen = id.charAt(4);//put a hyphen in the middle
		if (id.length() == 9  && numbers == 8)
		 {
			 Lno = id;// studentID
			System.out.println("Valid");
		}
		else 
		{
			System.out.println("studentID is not valid. ");
		}
	}
 
	//Get methods
	public String getFullName()
	 {
		String fullName;
		if (MiddleN.matches(""))
		 {
			fullName = FName + " " + LastN;
		}
		else {
			fullName = FName + " " + MiddleN +  " " + LastN;
		}
		return fullName;
	}
 
	public String getstudentID()
	 {
		return Lno;//studentID;
	}
 
	public void  getgender(String female, String Female)
	{
		if(gender ==female || gender ==Female)
			System.out.print("female");
			else
				System.out.print("male");
	}
	// public String getwrite()
// 	{
// 		return Student();
// 	}
 
	//toString method
	public String toString()
	 {
		return "studentID" + Lno + "Name: " + FName + " " + MiddleN + " " + LastN + "Mark " + Mark1 + "Mark" + Mark2 + "Mark" + Mark3 + "Gender " + gender + "\n";
	}
}

and the tester/////////

import java.util.InputMismatchException;
import java.io.*;
import java.util.Scanner;
   public class WriteStudentData
   {
 
      public static void main(String[] args) throws Exception
      {
         Scanner keyIn=new Scanner (System.in);
         Student s = new Student();
 
 
 
 
         //Create a file object called student.txt
            java.io.File file = new java.io.File("student.txt");             
         // Create file
            java.io.PrintWriter output = new java.io.PrintWriter(file);   
         // Write  to the student textfile
 
            output.println("L00012322 Mary Smith 99.1 47.5 66.5 Female");
            output.println("L00022211 Paul O Donnell 17.5 99.1 47.5 Male");
            output.println("L00033333 Anne Marie McLaughlin 100 100 100 Female");
            output.println("L00033345 Sean Dunne 99.1 99.1 0 Male");
         // Close the file
            output.close();
            try{//open a named file (Student)							            
               FileInputStream fstream = new FileInputStream("student.txt");
 
            // Get the object of DataInputStream
               DataInputStream in = new DataInputStream(fstream);
               BufferedReader br = new BufferedReader(new InputStreamReader(in));
               String strLine;
            //Read File Line By Line
               while ((strLine = br.readLine()) != null)  
					 {
               // Print the content on the console
                  System.out.println (strLine);
                }
            //Close the input stream
               in.close();
            }
               catch (Exception e){//Catch exception if any
                  System.err.println("Error: " + e.getMessage());
            }
			try
			{
    		String data = "S123456 John Paul Smith, 100, 100, 100, Male\n";
 
    		    		if(!file.exists())
			{
    			file.createNewFile();//if file doesnt exists, then create it. if it exists write to it/overwrite it
 
    		}
    		//true = append file
     	   	FileWriter fileWriter = new FileWriter(file.getName(),true);
    	        BufferedWriter bufferWriter = new BufferedWriter(fileWriter);
    	        bufferWriter.write(data);
    	        bufferWriter.close();
 
	        System.out.println("\n You have added a new student to file \n" +data +"\n\n");
 			output.close();
 
      	}
			catch(IOException e){
    		  e.printStackTrace();
			 }
 
			System.out.println("\tPlease select option: ");
 
		int option=0;
		do
		{
			//display menu
			System.out.println("\n\t\t----Options ----");//maybe add lno here
			System.out.println("\t1. Add Student" );
			System.out.println("\t2. Find Average ");
			System.out.println("\t3. Find female");
			System.out.println("\t4. Find Male");
			System.out.println("\t5. Information on file setup");//maybe view files
 
			System.out.println("\tQ. Quit");
			option = keyIn.nextInt();
			switch(option)
 
 
 
			{
			case 1:
 					int method=0;
				do
				{
 
           try
			  {
               System.out.print ("\tENTER STUDENT DETAILS\n\n");
 
					System.out.print ("\tEnter Student L Number\n\n");
               String Lno = keyIn.next(); 
					//while(!keyIn.hasNextLine ([A-Z a_z]);
				  // if (!keyIn.hasNextLine()) 
					//throw new BadDataException();
					System.out.print ("\t Eenter Student first Name\n\n");
               String FName = keyIn.next();
					// if (!keyIn.hasNextLine()) 
					//throw new BadDataException("Student first name only");*/
					System.out.print ("\t Enter Student Middle Name\n\n");
               String MiddleN = keyIn.next();
					// if (!keyIn.hasNextLine()) 
					//throw new BadDataException("Student Middle name if he has one");*/
					System.out.print ("\t Enter Student Last Name\n\n");
               String LastN = keyIn.next();
					// if (!keyIn.hasNextLine()) 
					//throw new BadDataException("Student Last name only");*/
					System.out.print ("\t Enter Students Mark1 result\n\n");
               double Mark1 = keyIn.nextDouble();
					System.out.print ("\t Enter Students Mark2 result\n\n");
               double Mark2 = keyIn.nextDouble();
					System.out.print ("\t Enter Student Mark3 result\n\n");
               double Mark3 = keyIn.nextDouble(); 
					System.out.printf("\t Enter Students Gender\n\n");
               String data = keyIn.next();
	           //if file doesnt exists, then create it
              if(!file.exists())
				  {// if it exists write to it else write a new file
                 file.createNewFile();
	           }            
            //true = append file
              FileWriter fileWriter = new FileWriter(file.getName(),true);
              PrintWriter p = new PrintWriter(fileWriter);
			  		// p.write(Lno);
// 					p.write(" "+FName);
// 					p.write(" "+MiddleN);
// 					p.write(" "+LastN);
// 					p.write(" "+Mark1);
// 					p.write(" "+Mark2);
// 					p.write(" "+Mark3);
// 					p.write(" "+data);
//                p.close();
 
               System.out.println(" new student  added to record");            
           		} 
               catch(Exception e)
					{
               System.out.print("The  information you have entered is incorrect\n");
					}
					}while(method != 0);
					//System.exit(0);		
					break;							
				case 2:
			//  Create a file object called Average.txt
			  java.io.File file2 = new java.io.File("Average.txt");
			  // Create file
			 java.io.PrintWriter output2 = new java.io.PrintWriter(file2);	
			 output2.println("45"); //p.write(Lno);
			  output2.close(); 
 
				break;	
				case 3:
			//  Create a file object called Male.tx
			  java.io.File file3 = new java.io.File("Male.txt"); 
			 // Create file
 			  java.io.PrintWriter output3 = new java.io.PrintWriter(file3);
			 output3.println("45");
			  output3.close(); 
 
				break;
				case 4:
				//  Create a file object called Female.txt
			  java.io.File file4 = new java.io.File("Female.txt"); 
			  // Create file
 			  java.io.PrintWriter output4 = new java.io.PrintWriter(file4);
			 output4.println("45");
			  output.close(); 
 
				break;	
				// case 5://this can be done without/ maybe
// 				System.out.println("\t File created\n");
// 				System.out.println("\t File Readable " +  file.canRead());
// 				System.out.println("\t File Writeable " +  file.canWrite());
// 				System.out.println("\t Is a File  " +  file.isFile());
// 				System.out.println("\t Is Hidden " +  file.isHidden());
// 				System.out.println("\t Last Modified " +  file.lastModified());
// 				System.out.println("\t File Size " +  file.length()+"\n");
// 				file.renameTo(new File("studentFile"));			
// 				break;								
				default: 
			}//end switch
 
		}while(option != 0);
 
			   boolean done = false;
 
 
				              // System.out.print("Your information is incorrect");
       //  PrintWriter outFile = new PrintWriter(new BufferedWriter(new FileWriter(s)));
   		// printwriter is used to write characters to a file used for a while ie println print in system.out.print to screen
			// BufferedWriter gathers a bunch of charaters and write them all at one time
			//FileWriter is used to write stream of charaters to a file thats all it does"writes to the file that has been created
 
 
            }   
         }

I seem to be doing a lot of coding without getting many results, I hope someone can help me.
Thank you MartinMc

Thanks for that Norm but I need to input diffrent querys, 1 to list students and details, 1 to get student numbers with averages and 1 (or 2) to get listings by gender

Originally Posted by Norm

For easier testing that does not require user input, change the definition for the Scanner class to have ALL the input data that is needed to execute the code. For example:

         Scanner keyIn=new Scanner ("put the required input here\nAnother line\n"); //System.in);

With that definition (with the correct values) the tester will not have to enter any data
and the data the program reads will be the same for all testers.

Thanks for that Norm, I think I understand but now Im not sure where to put that part of the code, Ive had problems trying to input all together, thats why I put them in seperate statements

No, still having problems but thanks for making the effort. Ill have to give up on it,