How to use PrintWriter and File classes in Java?

2019-01-03 05:57发布

I am trying to understand PrintWriter for a small program I'm making, and I cant seem to get java to make the file and then write on it. When I execute the program below it gives me a Filenotfoundexeption error on line 9. It also fails to make the file in the directory that I specified. I am new to this so please try and keep the answers simple. I am using Eclipse.

import java.io.PrintWriter;
import java.io.File;

public class Testing {

  public static void main(String[] args) {

    File file = new File ("C:/Users/Me/Desktop/directory/file.txt");
    PrintWriter printWriter = new PrintWriter ("file.txt");
    printWriter.println ("hello");
    printWriter.close ();       
  }
}

11条回答
一夜七次
2楼-- · 2019-01-03 06:39

Well I think firstly keep whole main into try catch(or you can use as public static void main(String arg[]) throws IOException ) and then also use full path of file in which you are writing as

PrintWriter printWriter = new PrintWriter ("C:/Users/Me/Desktop/directory/file.txt");

all those directies like users,Me,Desktop,directory should be user made. java wont make directories own its own. it should be as

import java.io.*;
public class PrintWriterClass {

public static void main(String arg[]) throws IOException{
    PrintWriter pw = new PrintWriter("C:/Users/Me/Desktop/directory/file.txt");
    pw.println("hiiiiiii");
    pw.close();
}   

}
查看更多
疯言疯语
3楼-- · 2019-01-03 06:39

Double click the file.txt, then save it, command + s, that worked in my case. Also, make sure the file.txt is saved in the project folder. If that does not work.

PrintWriter pw = new PrintWriter(new File("file.txt"));
pw.println("hello world"); // to test if it works.
查看更多
爷的心禁止访问
4楼-- · 2019-01-03 06:40

The PrintWriter class can actually create the file for you.

This example works in JDK 1.7+.

// This will create the file.txt in your working directory.

PrintWriter printWriter = null;

try {

    printWriter = new PrintWriter("file.txt", "UTF-8");
    // The second parameter determines the encoding. It can be
    // any valid encoding, but I used UTF-8 as an example.

} catch (FileNotFoundException | UnsupportedEncodingException error) {
    error.printStackTrace();
}

printWriter.println("Write whatever you like in your file.txt");

// Make sure to close the printWriter object otherwise nothing
// will be written to your file.txt and it will be blank.
printWriter.close();

For a list of valid encodings, see the documentation.

Alternatively, you can just pass the file path to the PrintWriter class without declaring the encoding.

查看更多
神经病院院长
5楼-- · 2019-01-03 06:43

If you want to use PrintWrite then try this code

public class PrintWriter {
    public static void main(String[] args) throws IOException {

        java.io.PrintWriter pw=new java.io.PrintWriter("file.txt");
        pw.println("hello world");
        pw.flush();
        pw.close();

    }

}
查看更多
做个烂人
6楼-- · 2019-01-03 06:44
import java.io.PrintWriter;
import java.io.File;

public class Testing {

  public static void main(String[] args) throws IOException {

    File file = new File ("C:/Users/Me/Desktop/directory/file.txt");
    PrintWriter printWriter = new PrintWriter ("file.txt");
    printWriter.println ("hello");
    printWriter.close ();       
  }
}

throw an exception for the file.

查看更多
登录 后发表回答