How to read file from command line in java?

Question

I want to go to command line and type the input, so the BufferReader can have access to the file. How am i supposed to do that ?

The input will be "java TagMatching path_to_html_file.html"

// Importing only the classes we need
import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;

public class TagMatching {

    public static void main(String[] args) {

        BufferedReader br = null;    
        // try to read the file
        try {

            br = new BufferedReader(new FileReader(**/*DONT KNOW WHAT TO DO*/**));
            String line;                        

        } catch (IOException e) {
            e.printStackTrace();
        }

    }

}

Elaborate what you want to do, I mean not able to understand what u r actually looking for — Wasi, Nov 18 '15 at 12:48
Do you want to read all lines from a file and add them to a String? Is this file very big, so that you need buffering? — Beri, Nov 18 '15 at 12:48

Jordi Castilla · Answer 1 · 2015-11-18T13:10:43.060

The input will be java TagMatching path_to_html_file.html

After the name of the app (TagMatching) you find the arguments (path_to_html_file.html) this are the String[] args of the main method, so just use them, in this case args[0]:

public static void main(String[] args) {
    BufferedReader br = null;    
    // try to read the file
    try {
        // check if there are some arguments 
        if (null != args[0] && 
            // lenght > 5 because a.html will be shortest filename
            args[0].lenght > 5 && 
            // check if arguments have the correct file extension
            args[0].endsWith(".html")) 
        {
            br = new BufferedReader(new FileReader(args[0]));
            // do more stuff
        }
    } catch (IOException e) {
        e.printStackTrace();
    }
}

@Shivam what about reading **first line of my answer** before posting? `a.txt` **MUST** and **WILL** be ignored — Jordi Castilla, Nov 18 '15 at 13:05

score 0 · Answer 2 · answered Nov 18 '15 at 12:47

To get the input from the console you have to use Scanner like this;

Scanner in = new Scanner(System.in); 
System.out.println("Enter file path");
String s = in.nextLine(); //C:\\testing.txt

And to use that file path in the FIleReader use like this;

br = new BufferedReader(new FileReader(s));

score 0 · Answer 3 · answered Mar 30 '19 at 13:50

0

Exactly works with args[0].

So,br = new BufferedReader(new FileReader(args[0])); will act as the questioner intends

answered Mar 30 '19 at 13:50

Joey Cho

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How to read file from command line in java?

3 Answers3