Thread: File Input and Output and Exception Handling

I want to save the data I have entered into the arraylist into a text file, so I would probably create the file at the start? then go through the program and enter the details of the characters in the array and then when I save the character for its information to be added to the text file.

Also thank you for the reply <3

On each line would be something like this...
The user must enter a Name, Race, Age, Attack and Defense.

So there for each line would be...

Name:
Race:
Age:
Attack:
Defense:

and then skip a line and if another hero is added it will add their details too.

The file should probably be read when the user wants to so maybe by adding another choice onto the list of options I have in my program.
I don't really understand what you mean by what would they be used for? Sorry.

It is just to store a Team of Heroes created by the user.

If you intend to use the latest NIO code in Java 7, then these are the very basics:

Starting with the file path ...

//create a path for the file you intend to use. This one uses the name 'my_file.txt' and the default directory for the project. So if you use Eclipse, it will be the .../workspace/your_project directory.

Path p = Paths.get("my_file.txt");

Alternatively you could also point the path to your 'home' directory for your particular system (eg. on my Windows 7 PC this will be c:/users/Starstreak)

Path p = Paths.get(System.getProperty("user.home"), "my_file.txt");

Okay, so I made a program where I use a pre made text file and then it prints its contents to the screen and creates a new text file...
But I still don't really understand it.
How am I supposed to combine this with my other program to achieve my goal?

package HeroCreation;

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;

public class FileIO {

public String readTextFile(String fileName) {
String returnValue = "";
FileReader file = null;
String line = "";
try {
file = new FileReader(fileName);
BufferedReader reader = new BufferedReader(file);
while ((line = reader.readLine()) != null) {
returnValue += line + "\n";
}
} catch (FileNotFoundException e) {
throw new RuntimeException("File not found");
} catch (IOException e) {
throw new RuntimeException("IO Error occured");
} finally {
if (file != null) {
try {
file.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
return returnValue;
}

public void writeTextFile(String fileName, String s) {
FileWriter output = null;
try {
output = new FileWriter(fileName);
BufferedWriter writer = new BufferedWriter(output);
writer.write(s);
} catch (IOException e) {
e.printStackTrace();
} finally {
if (output != null) {
try {
output.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}


}
}

package HeroCreation;
public class Main {
public static void main(String[] args) {
FileIO myFile = new FileIO();
String input = myFile.readTextFile("Testing.txt");
System.out.println(input);
myFile.writeTextFile("Testing2.txt", input);
}
}

Originally Posted by Norm

Please use code tags to surround the code, note quote tags.


What part of the code are you having problems with?

Sorry about that! I just don't know how to implement it in the original code to get it to work? Is that code sufficient to get the program working the way I want, how else do I add onto it?

You have a few lines of data that relates to one 'Hero'.

You can create a series of seperate methods to write the information to file. Say, one for reading, one for writing ...

Things to consider:

To use NIO2 or the older Java API.

Code to check if the file exists and is writeable.

Code to create the file.

Whether to store data in a fresh file, one for each person?
or
Add the record to one big file? You would then have to think of how to extract/amend/delete specific lines.

Okay, so I have been working on the code, it now requests user input on what option you want to choose, if you choose "add hero" option, a prompt comes up to enter a name, then an age then a race. When done, there is a println saying Hero added and then a description on the hero "Hero "Name" was added who is "age" years old and of the "race" race." This bit of information is saved to the binary.dat file decalred at the start and when you add another hero this line aswell as the new hero created line will come up. This is too saved in the binary.dat file...

So my question is, how do I read the file at the start to ADD to the file even after the program is closed, so I can edit the contents whenever.

package myHero;
 
/*The aim of this project is to allow the user to input data which will give structure to a character known as HERO. 
 There can be several Heroes, more can be added using the create a Hero method.*/
import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.EOFException;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import java.util.Random;
import java.util.Scanner;
 
//Creates a class with the Scanner for user input and also declares the ArrayLists for each element of the Hero we are to create.
public class HeroCreate {
 
    DataOutputStream outFile;
    DataInputStream inFile;
    String datafile = "binarydata.dat";
    Scanner input = new Scanner(System.in);
    //Elements of the Hero such as Name, Attack and Defense. 
    List<String> hName = new ArrayList<>();
    List<Integer> hAge = new ArrayList<>();
    List<String> hRace = new ArrayList<>();
    List<Integer> hAttack = new ArrayList<>();
    List<Integer> hDefense = new ArrayList<>();
 
//This acts as the HUB for the user to enter in a number to choose from the options in the list.
    public void StartPanel() throws IOException {
        System.out.println("\n" + "WELCOME TO HERO CREATOR!");
        System.out.println("1. Create a Hero Now!");
        System.out.println("2. Delete An Existing Hero?");
        System.out.println("3. Show Current Heroes!");
        System.out.println("4. Exit Menu ");
 
        //This is where the program identifies which number the user has chosen and links them to the next method.
        int choice = input.nextInt();
 
        if (choice == 1) {
            CreateHero();
        } else if (choice == 2) {
            DeleteHero();
            ShowTeam();
        } else if (choice == 3) {
            ShowTeam();
            StartPanel();
        } else if (choice == 4) {
            StopPro();
        } else {
            System.out.println("Error!");
            StartPanel();
        }
 
 
 
    }
 
//This is class which allows for the user to create the HERO, giving it all of its details. 
//When the user enters the details it is stored in an array corresponding to its role. i.e NAME in the hName arrayList.
    public void CreateHero() throws IOException {
        System.out.print("Name Your Hero: ");
        input.nextLine();
        String newHeroName = input.nextLine();
        hName.add(newHeroName);
 
        System.out.print("How Old Is Your Hero?: ");
        int newHeroAge = input.nextInt();
        hAge.add(newHeroAge);
 
        System.out.print("Which Race is your Hero?: ");
        input.nextLine();
        String newHeroRace = input.nextLine();
        hRace.add(newHeroRace);
 
//The following assigns random values between 1 and 100 to the Attack and Defense element of the HERO.
        int min = 0;
        int max = 100;
        Random r = new Random();
 
        int newHeroAtt = r.nextInt(max - min + 1) + min;
        hAttack.add(newHeroAtt);
 
        int newHeroDef = r.nextInt(max - min + 1) + min;
        hDefense.add(newHeroDef);
 
 
//A println to declare a character has been added.
        System.out.println("\n" + "The Hero " + hName.get(hName.size() - 1) + " Was Added!" + "\n");
 
        try {
 
            outFile = new DataOutputStream(new BufferedOutputStream(new FileOutputStream(datafile)));
 
            for (int x = 0; x < hName.size(); x++) {
                outFile.writeUTF(hName.get(x));
                outFile.writeInt(hAge.get(x));
                outFile.writeUTF(hRace.get(x));
                outFile.writeInt(hAttack.get(x));
                outFile.writeInt(hDefense.get(x));
            }
            outFile.close();
        } catch (FileNotFoundException fnf) {
            System.out.println("Error! The File " + datafile + " cannot be located.");
        } catch (IOException ioe) {
            System.out.println("Error! An IO Excpetion has happened.");
        }
 
        try {
            inFile = new DataInputStream(new BufferedInputStream(new FileInputStream(datafile)));
 
 
            String tempName = "";
            String tempRace = "";
            int tempAge = 0;
            int tempAttack = 0;
            int tempDefense = 0;
 
            while (true) {
                tempName = inFile.readUTF();
                tempAge = inFile.readInt();
                tempRace = inFile.readUTF();
                tempAttack = inFile.readInt();
                tempDefense = inFile.readInt();
                System.out.format("The Hero %s is %d years old and is of the %s race, with an attack of %d and a defense of %d.%n", tempName, tempAge, tempRace, tempAttack, tempDefense);
            }
        } catch (FileNotFoundException fnf) {
            System.out.println("Error! The file " + datafile + "cannot be located.");
        } catch (EOFException e) {
            System.out.format("%nFile Successfully Updated!%n");
 
 
 
        }
 
 
 
 
//A choice to continue creating Heroes or to return to the main menu.
        System.out.println("Add Another Hero?");
        System.out.println("1. Create Another Hero!");
        System.out.println("2. Return to Main Menu.");
 
        int choice = input.nextInt();
 
        if (choice == 1) {
            CreateHero();
        } else if (choice == 2) {
            StartPanel();
        }
    }
 
//This method allows for a Hero to be deleted for whatever reason, by removing the elements of a Hero and deleting it from the arrayList.
    public void DeleteHero() throws IOException {
        ShowTeam();
        System.out.println(" Which Hero Will Be Deleted? (1 to " + hName.size() + ")");
        int delete = input.nextInt();
        if (delete > hName.size()) {
            System.out.println("That is not a choice!");
            StartPanel();
        } else {
            delete--;
            System.out.println("Would you like to delete the following hero?: " + hName.get(delete));
            System.out.print("1 for YES or 2 for NO" + "\n");
            int confirmDelete = input.nextInt();
            if (confirmDelete == 1) {
                hName.remove(delete);
                hAge.remove(delete);
                hRace.remove(delete);
                hAttack.remove(delete);
                hDefense.remove(delete);
                System.out.println("Hero has been deleted!");
                StartPanel();
            } else {
                StartPanel();
            }
 
        }
    }
 
//This is a useful method which allows the user to view all current Hero characters in the ArrayList.
    public void ShowTeam() {
        System.out.println("\n");
        for (int i = 0; i < hName.size(); i++) {
            int counter = i + 1;
            System.out.println("H E R O   " + counter);
            System.out.println("-------------------------");
            System.out.println("Name: " + hName.get(i) + "\n" + " Age: " + hAge.get(i) + "\n" + " Race: " + hRace.get(i) + "\n" + " Attack: " + hAttack.get(i) + "\n" + " Defense: " + hDefense.get(i) + "\n" + "\n");
        }
    }
 
//This stops the program from running.
    static void StopPro() {
        System.out.println("Ended");
        System.exit(0);
    }
}
 
//This is the main body which envokes the program
class Hero {
 
    public static void main(String[] args) throws IOException {
 
        HeroCreate heroChar = new HeroCreate();
 
        heroChar.StartPanel();
    }
}

Hi, So I have been working on the project more, it is due tommorow at 12 noon.
One final question I think, My code reads the information put in by the user which is in seperate arraylists, such as an array list for the names, array lists for the ages and so on.
The information is saved to a binary file at the end of the program, now for my question.
How do I read in the information from the file upon starting back up the program, like my program cant access the information I have stored previously, It can read back the data IN THE file as text but cant access them in a way such as...

One of my choices is "view heroes" but when I choose it, it acts as though there are no objects in the array?

package myHero;
 
/*The aim of this project is to allow the user to input data which will give structure to a character known as HERO. 
 There can be several Heroes, more can be added using the create a Hero method.*/
import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.EOFException;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import java.util.Random;
import java.util.Scanner;
 
//Creates a class with the Scanner for user input and also declares the ArrayLists for each element of the Hero we are to create.
public class HeroCreate {
 
 
 
    DataOutputStream outFile;
    DataInputStream inFile;
    String datafile = "binarydata.dat";
    Scanner input = new Scanner(System.in);
    //Elements of the Hero such as Name, Attack and Defense. 
    List<String> hName = new ArrayList<>();
    List<Integer> hAge = new ArrayList<>();
    List<String> hRace = new ArrayList<>();
    List<Integer> hAttack = new ArrayList<>();
    List<Integer> hDefense = new ArrayList<>();
 
//This acts as the HUB for the user to enter in a number to choose from the options in the list.
    public void StartPanel() throws IOException {
        System.out.println("\n" + "WELCOME TO HERO CREATOR!");
        System.out.println("1. Create a Hero Now!");
        System.out.println("2. Delete An Existing Hero?");
        System.out.println("3. Show Current Heroes!");
        System.out.println("4. Exit Menu ");
 
        //This is where the program identifies which number the user has chosen and links them to the next method.
        int choice = input.nextInt();
 
        if (choice == 1) {
            CreateHero();
        } else if (choice == 2) {
            DeleteHero();
            ShowTeam();
        } else if (choice == 3) {
            ShowTeam();
            StartPanel();
        } else if (choice == 4) {
            StopPro();
        } else {
            System.out.println("Error!");
            StartPanel();
        }
 
 
 
    }
 
//This is class which allows for the user to create the HERO, giving it all of its details. 
//When the user enters the details it is stored in an array corresponding to its role. i.e NAME in the hName arrayList.
    public void CreateHero() throws IOException {
        System.out.print("Name Your Hero: ");
        input.nextLine();
        String newHeroName = input.nextLine();
        hName.add(newHeroName);
 
        System.out.print("How Old Is Your Hero?: ");
        int newHeroAge = input.nextInt();
        hAge.add(newHeroAge);
 
        System.out.print("Which Race is your Hero?: ");
        input.nextLine();
        String newHeroRace = input.nextLine();
        hRace.add(newHeroRace);
 
//The following assigns random values between 1 and 100 to the Attack and Defense element of the HERO.
        int min = 0;
        int max = 100;
        Random r = new Random();
 
        int newHeroAtt = r.nextInt(max - min + 1) + min;
        hAttack.add(newHeroAtt);
 
        int newHeroDef = r.nextInt(max - min + 1) + min;
        hDefense.add(newHeroDef);
 
 
//A println to declare a character has been added.
        System.out.println("\n" + "The Hero " + hName.get(hName.size() - 1) + " Was Added!" + "\n");
 
        try {
 
            outFile = new DataOutputStream(new BufferedOutputStream(new FileOutputStream(datafile)));
 
            for (int x = 0; x < hName.size(); x++) {
                outFile.writeUTF(hName.get(x));
                outFile.writeInt(hAge.get(x));
                outFile.writeUTF(hRace.get(x));
                outFile.writeInt(hAttack.get(x));
                outFile.writeInt(hDefense.get(x));
            }
            outFile.close();
        } catch (FileNotFoundException fnf) {
            System.out.println("Error! The File " + datafile + " cannot be located.");
        } catch (IOException ioe) {
            System.out.println("Error! An IO Excpetion has happened.");
        }
 
        try {
            inFile = new DataInputStream(new BufferedInputStream(new FileInputStream(datafile)));
 
 
            String tempName = "";
            String tempRace = "";
            int tempAge = 0;
            int tempAttack = 0;
            int tempDefense = 0;
 
            while (true) {
                tempName = inFile.readUTF();
                tempAge = inFile.readInt();
                tempRace = inFile.readUTF();
                tempAttack = inFile.readInt();
                tempDefense = inFile.readInt();
                System.out.format("The Hero %s is %d years old and is of the %s race, with an attack of %d and a defense of %d.%n", tempName, tempAge, tempRace, tempAttack, tempDefense);
            }
        } catch (FileNotFoundException fnf) {
            System.out.println("Error! The file " + datafile + "cannot be located.");
        } catch (EOFException e) {
            System.out.format("%nFile Successfully Updated!%n");
 
 
 
        }
 
 
 
 
//A choice to continue creating Heroes or to return to the main menu.
        System.out.println("Add Another Hero?");
        System.out.println("1. Create Another Hero!");
        System.out.println("2. Return to Main Menu.");
 
        int choice = input.nextInt();
 
        if (choice == 1) {
            CreateHero();
        } else if (choice == 2) {
            StartPanel();
        }
    }
 
//This method allows for a Hero to be deleted for whatever reason, by removing the elements of a Hero and deleting it from the arrayList.
    public void DeleteHero() throws IOException {
        ShowTeam();
        System.out.println(" Which Hero Will Be Deleted? (1 to " + hName.size() + ")");
        int delete = input.nextInt();
        if (delete > hName.size()) {
            System.out.println("That is not a choice!");
            StartPanel();
        } else {
            delete--;
            System.out.println("Would you like to delete the following hero?: " + hName.get(delete));
            System.out.print("1 for YES or 2 for NO" + "\n");
            int confirmDelete = input.nextInt();
            if (confirmDelete == 1) {
                hName.remove(delete);
                hAge.remove(delete);
                hRace.remove(delete);
                hAttack.remove(delete);
                hDefense.remove(delete);
                System.out.println("Hero has been deleted!");
                StartPanel();
            } else {
                StartPanel();
            }
 
        }
    }
 
//This is a useful method which allows the user to view all current Hero characters in the ArrayList.
    public void ShowTeam() {
        System.out.println("\n");
        for (int i = 0; i < hName.size(); i++) {
            int counter = i + 1;
            System.out.println("H E R O   " + counter);
            System.out.println("-------------------------");
            System.out.println("Name: " + hName.get(i) + "\n" + " Age: " + hAge.get(i) + "\n" + " Race: " + hRace.get(i) + "\n" + " Attack: " + hAttack.get(i) + "\n" + " Defense: " + hDefense.get(i) + "\n" + "\n");
        }
    }
 
//This stops the program from running.
    static void StopPro() {
        System.out.println("Ended");
        System.exit(0);
    }
}
 
//This is the main body which envokes the program
class Hero {
 
    public static void main(String[] args) throws IOException {
        DataOutputStream outFile;
        DataInputStream inFile;
        String datafile = "binarydata.dat";
        try {
            inFile = new DataInputStream(new BufferedInputStream(new FileInputStream(datafile)));
 
 
            String tempName = "";
            String tempRace = "";
            int tempAge = 0;
            int tempAttack = 0;
            int tempDefense = 0;
 
            while (true) {
                tempName = inFile.readUTF();
                tempAge = inFile.readInt();
                tempRace = inFile.readUTF();
                tempAttack = inFile.readInt();
                tempDefense = inFile.readInt();
                System.out.format("The Hero %s is %d years old and is of the %s race, with an attack of %d and a defense of %d.%n", tempName, tempAge, tempRace, tempAttack, tempDefense);
            }
        } catch (FileNotFoundException fnf) {
            System.out.println("Error! The file " + datafile + "cannot be located.");
        } catch (EOFException e) {
            System.out.format("%nThis was the last information put through the file!%n");
 
 
 
        }
 
        HeroCreate heroChar = new HeroCreate();
 
 
        heroChar.StartPanel();
    }
}

Well there should be objects in the array, I made an array list for name, age, race, attakc and defense each. I then wrote them to the file, they read back perfectly fine but when I reopen the file in the program I want it to be able to read the same information without me re entering it. So basiaclly straight from the file.

Awesome, thanks! Do you have any idea where I could find a tutorial for that? Really strapped for time.

Thanks so much for all your help, you're brilliant <3