file i/o with Java

Question

So I have a background in c++ and I am trying to learn java. Everything is pretty similar. I am having a problem thought with file i/o. So I am messing around and doing really simple programs to get the basic ideas. Here is my code to write data to a file. My code makes a file, but when I open the file it is empty and does not contain the string I told it to write.

 package practice.with.arrays.and.io;

 import java.io.IOException;
 import java.io.PrintWriter;

 public class PracticeWithArraysAndIO 
 {

 public static void main(String[] args) throws IOException
  {
    //Declaring a printWriter object
    PrintWriter out  = new PrintWriter("myFile.txt");

    out.println("hello");
 }

 }

Answer 1

The output is buffered and needs to be flush() ed to be written to a file.

package practice.with.arrays.and.io;

import java.io.IOException;
import java.io.PrintWriter;

public class PracticeWithArraysAndIO {

    public static void main(String[] args) {
        PrintWriter out = new PrintWriter("myFile.txt");
        out.println("hello");
        out.flush();
    }

}

But you don't need to flush explicitly because that will happen anyway when you close() the writer, which you ought to be doing.

package practice.with.arrays.and.io;

import java.io.IOException;
import java.io.PrintWriter;

public class PracticeWithArraysAndIO {

    public static void main(String[] args) {
        PrintWriter out = new PrintWriter("myFile.txt");
        try {
            out.println("hello");
        } finally {
            out.close();
        }
    }

}

But you also don't need to close explicitly because PrintWriter implements AutoCloseable , so you can use Java 7's automatic resource management:

package practice.with.arrays.and.io;

import java.io.IOException;
import java.io.PrintWriter;

public class PracticeWithArraysAndIO {

    public static void main(String[] args) {
        try (PrintWriter out = new PrintWriter("myFile.txt")) {
            out.println("hello");
        }
    }

}