JSP, Tomcat, JDBC, Projects, Example, Program » java.io

Java I/O Stream

admin — Tue, 17 May 2011 07:40:23 +0000

By: Pankaj Yadav

It can be used to write the data on file. It provides us methods to perform various tasks on the file. In order to use this class we have to import java.IO package.

Syntax:

import java.io.*;

In this package we have input stream and output stream for read and write in a file.

Input Stream

The java.io.InputStream is the base class of the input streams in java .The input stream read data form a file with the help of read() method. The read() method returns integer type value. If read() method does not have any byte to read returns the -1.

Example:

InputStream inputs = new FileInputStream("c://data//file.txt");
int _idata = inputs.read();
while( _idata> -1 )
{
_idata = inputs.read();
}

Output Stream

The java.io.OutputStream is the base class of the output streams in java. The write() method is used to write the data in the file .

Example:

import java.io.FileOutputStream;
import java.io.OutputStream;

public class OutputStreamExample {

	public static void main(String[] args) {

		try{
			OutputStream out = new FileOutputStream("c://file.txt");
			out.write("testOutputstream".getBytes());
			out.close();
		}
		catch(Exception e)
		{
			e.printStackTrace();
		}
	}

}

We can also use these streams in the sequence to perform the different tasks. This class also provides the buffering techniques for faster performance.

Java – Read file without DataInputStream

admin — Sun, 20 Dec 2009 13:45:21 +0000

Read File in java without DataInputStream class. DataInputStream class is deprecated. Instead of DataInputStream class we can use BufferedReader to read file in java.

This example will explain read file in java.

import java.io.File;
import java.io.FileInputStream;
import java.io.BufferedReader;
import java.io.InputStreamReader;

public class JavaReadFileExample {

    public static void main(String[] args) {

        File f=new File("c:\\readFileinJava.txt");

        try {
            FileInputStream fs = new FileInputStream(f);
            InputStreamReader in = new InputStreamReader(fs);
            BufferedReader br = new BufferedReader(in);

            String text;

            while(true)
            {
                text=br.readLine();
                if(text==null)
                    break;
                System.out.println(text);
            }
        }
        catch (Exception e) {
            e.printStackTrace();
        }
    }
}

Java – Run shell command in java

admin — Sun, 20 Dec 2009 13:33:13 +0000

Execute Shell command can be run by Runtime class. Shell can be executed in linux or unix platform.

This example will explain how to run shell commands in java and execute commands in java.

public class JavaRunCommandExample {

    public static void main(String[] args) {

        Runtime r = Runtime.getRuntime();
        Process p = null;
        String cmd[] = {"/bin/sh","ls","-l"};

        try {
            p = r.exec(cmd);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

Java – Edit File Example, Modify File java

admin — Sun, 20 Dec 2009 10:02:19 +0000

File can be appended by File class and other input output stream. To write content in a file in java we need to use java.io package. File class is used to create a file at specific path. We can use either StringBuffer for text and content to store in file. In java we can write file with FileWriter class with BufferedWriter class. write() method is used to create file and write the content in file.

To edit file in java we need to search text which replace with new text. indexOf() method will search text in java and append() method will modify old content in string.

This example will explain how to edit file in java and modify text in file by java.

text file in c drive

Content in this text, abc change xyz with new content by java io package

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileWriter;
import java.io.IOException;
import java.io.InputStreamReader;

public class JavaIOEditFileExample {

    public static void main(String[] args) {

        File f=new File("c:\\appendOldFile.txt");

        FileInputStream fs = null;
        InputStreamReader in = null;
        BufferedReader br = null;

        StringBuffer sb = new StringBuffer();

        String textinLine;

        try {
             fs = new FileInputStream(f);
             in = new InputStreamReader(fs);
             br = new BufferedReader(in);

            while(true)
            {
                textinLine=br.readLine();
                if(textinLine==null)
                    break;
                sb.append(textinLine);
            }
              String textToEdit1 = "abc";
              int cnt1 = sb.indexOf(textToEdit1);
              sb.replace(cnt1,cnt1+textToEdit1.length(),"New Append text");

              String textToEdit2 = "xyz";
              int cnt2 = sb.indexOf(textToEdit2);
              sb.replace(cnt2,cnt2+textToEdit2.length(),"Second new edit text");

              fs.close();
              in.close();
              br.close();

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

            try{
                FileWriter fstream = new FileWriter(f);
                BufferedWriter outobj = new BufferedWriter(fstream);
                outobj.write(sb.toString());
                outobj.close();

            }catch (Exception e){
              System.err.println("Error: " + e.getMessage());
            }
    }
}

Output

Content in this text, New Append text change Second new edit text with new content by java io package

Java – How to Write text file, Write Content in File

admin — Mon, 14 Dec 2009 13:44:58 +0000

To write content in a file in java we need to use java.io package. File class is used to create a file at specific path. We can use either StringBuffer or StringBuilder for text and content to store in file. In java we can write file with FileWriter class with BufferedWriter class. write() method is used to create file and write the content in file.

Example will explains how to write text a file in java

import java.io.BufferedWriter;
import java.io.File;
import java.io.FileWriter;

public class JavaIOWriteTextFileExample {

    public static void main(String[] args) {

        File f=new File("c:\\writeContentfile.txt");

        StringBuffer sb = new StringBuffer("Text Content to write in java file");
        try{
            FileWriter fwriter = new FileWriter(f);
            BufferedWriter bwriter = new BufferedWriter(fwriter);
            bwriter.write(sb.toString());
            bwriter.close();
         }
        catch (Exception e){
              e.printStackTrace();
         }
    }
}

Java – How to Create file in Java

admin — Mon, 14 Dec 2009 13:27:39 +0000

To create a file in java we need to use java.io package. File class is used to create a file at specific path. In java we can write file with FileWriter class with BufferedWriter class. write() method is used to create file and write the content in file.

Example will explain how to create a file in java and how to write file in Java

import java.io.File;
import java.io.FileWriter;
import java.io.BufferedWriter;

public class JavaIOWriteFileExample {

    public static void main(String[] args) {

        File f=new File("c:\\createNewfile.txt");

        try{
            FileWriter fstreamCopy = new FileWriter(f);
            BufferedWriter outobjCopy = new BufferedWriter(fstreamCopy);
            outobjCopy.write("The content write to inside the file");
            outobjCopy.close();
         }
        catch (Exception e){
              e.printStackTrace();
         }
    }
}

JSP, Tomcat, JDBC, Projects, Example, Program » java.io

Java I/O Stream

Input Stream

Output Stream

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