Initial Commit

Demo of how to read from and write to files

.classpath

+<?xml version="1.0" encoding="UTF-8"?>
+<classpath>
+	<classpathentry kind="con" path="org.eclipse.jdt.launching.JRE_CONTAINER/org.eclipse.jdt.internal.debug.ui.launcher.StandardVMType/JavaSE-1.8"/>
+	<classpathentry kind="src" path="src"/>
+	<classpathentry kind="output" path="bin"/>
+</classpath>

.gitignore

+/bin/

.project

+<?xml version="1.0" encoding="UTF-8"?>
+<projectDescription>
+	<name>FileAccess</name>
+	<comment></comment>
+	<projects>
+	</projects>
+	<buildSpec>
+		<buildCommand>
+			<name>org.eclipse.jdt.core.javabuilder</name>
+			<arguments>
+			</arguments>
+		</buildCommand>
+	</buildSpec>
+	<natures>
+		<nature>org.eclipse.jdt.core.javanature</nature>
+	</natures>
+</projectDescription>

.settings/org.eclipse.jdt.core.prefs

+eclipse.preferences.version=1
+org.eclipse.jdt.core.compiler.codegen.inlineJsrBytecode=enabled
+org.eclipse.jdt.core.compiler.codegen.targetPlatform=1.8
+org.eclipse.jdt.core.compiler.codegen.unusedLocal=preserve
+org.eclipse.jdt.core.compiler.compliance=1.8
+org.eclipse.jdt.core.compiler.debug.lineNumber=generate
+org.eclipse.jdt.core.compiler.debug.localVariable=generate
+org.eclipse.jdt.core.compiler.debug.sourceFile=generate
+org.eclipse.jdt.core.compiler.problem.assertIdentifier=error
+org.eclipse.jdt.core.compiler.problem.enumIdentifier=error
+org.eclipse.jdt.core.compiler.source=1.8

me.txt

+First line to file
+Second line to file
+Third line to file
+Fourth line to file
+Output number 0
+Output number 1
+Output number 2
+Output number 3
+Output number 4

src/FileHandler.java

+import java.io.File;
+import java.io.FileNotFoundException;
+import java.io.PrintWriter;
+import java.util.Scanner;
+
+public class FileHandler {
+
+	File file = null;			// fh forms a connection to a file but does not open it
+	PrintWriter pw = null;		// pw is used to open a file for writing, write to it and close it after
+	Scanner sc=null;			// sc is used to open a file for reading, read from it and close it after
+
+	// Class constructor - mkaes connection to a file
+	public FileHandler(String filename)
+	{
+		file = new File(filename);
+		
+	}
+	
+	// open a file for writing. Exit elegantly if we cannot open the file
+	public void prepare_to_write()
+	{
+		try 
+		{
+	      // Connect the a PrintWriter Object to our file
+	      // If it fails it will trigger a FileNotFoundException
+	      // which will be handled by the catch
+	      pw = new PrintWriter(file);
+	    }
+	    catch (FileNotFoundException e)
+	    {
+	      System.out.println("Program is closing, unable to create file.");
+	      System.exit(-1); // Terminates program
+	    }
+	}
+
+	// open a file for reading. Exit elegantly if we cannot open the file
+	public void prepare_to_read()
+	{
+		try
+		{
+		  sc = new Scanner(file);
+		}
+		catch (FileNotFoundException e) 
+		{
+		      System.out.println("Program is closing, unable to read file.");
+		      System.exit(-1); // Terminates program
+	    }
+	}
+	
+	// Writes a string to the next line in the file.
+	// NB must have used prepare_to_write() before you can write_to_file()
+	public void write_to_file(String text)
+	{
+		pw.println(text);
+	}
+	
+	// checks to see if we have reached the end of a file we have opened for reading
+	public Boolean end_of_file()
+	{
+		return !(sc.hasNextLine());
+	}
+	
+	// returns the next line from a file as a string
+	// NB must have used prepare_to_read() before you can read_line_from_file()
+	public String read_line_from_file()
+	{
+		return sc.nextLine();
+	}
+	
+	// close a file that was opened for writing
+	public void end_writing()
+	{
+		pw.close();
+	}
+	
+	// close a file that was opened for reading
+	public void end_reading()
+	{
+		sc.close();
+	}	
+}

src/MainClass.java

+
+public class MainClass {
+
+	
+	
+	
+	public static void main(String[] args) {
+		// TODO Auto-generated method stub
+
+		// Creates an object linked to a file but doesn't actually open it
+		FileHandler fh = new FileHandler("me.txt");
+		
+		// opens the file for writing
+		fh.prepare_to_write();
+		
+		// writes text to the file
+		fh.write_to_file("First line to file");
+		fh.write_to_file("Second line to file");
+		fh.write_to_file("Third line to file");
+		fh.write_to_file("Fourth line to file");
+		
+		for (int i=0; i<5; i++)
+		{
+			fh.write_to_file("Output number " + i);
+		}
+		
+		
+		// remember to do this when you are finished
+		// closes the file (when writing)
+		fh.end_writing();
+		
+		
+		// Open the file for reading
+		// Note because we have already connected the FileHandler fh to a file we
+		// are simply using that again. 
+		// You would need to connect to a file if you hadn't already
+		fh.prepare_to_read();
+
+		String tempString = "";
+		// check to see if we've reached the end of the line
+		while (!fh.end_of_file())
+		{
+			// read a line of text from the file
+			tempString = fh.read_line_from_file();
+			// you might need to process this if you are reading specific data
+			System.out.println(tempString);
+		}
+		
+		// Close the file when we are finished reading
+		fh.end_reading();
+		
+	}
+
+}