How do I delete a file in Java?

By I Wayan Saryada in Core API, IO 0 Comment

In this example you will see how to delete a file in Java. To delete a file we start by creating a File object that represent the file to be deleted. We use the exists() method to check if the file is exists before we try to delete it.

To delete the file we call the delete() method of the File object. If the file was successfully deleted the method will return a boolean true result, otherwise it will return false. Let’s try the code snippet below.

package org.kodejava.io;

import java.io.File;

public class FileDeleteExample {
    public static void main(String[] args) {
        // When want to delete a file named readme.txt
        File file = new File("write.txt");

        // Checks if the file is exists before deletion.
        if (file.exists()) {
            System.out.println("Deleting " + file.getAbsolutePath());
            // Use the delete method to delete the given file.
            boolean deleted = file.delete();
            if (deleted) {
                System.out.println(file.getAbsolutePath() + " was deleted.");
            }
        } else {
            System.out.println(file.getAbsolutePath() + " not found.");
        }
    }
}

How do I write string data to file?

By I Wayan Saryada in Apache Commons, Commons IO 0 Comment

The following code snippet shows you how to write strings of data into a file using the Apache Commons IO library. We can use the FileUtils.writeStringToFile() method to do it. This method accepts the file object where the data will be stored, the data itself, and the encoding.

package org.kodejava.commons.io;

import org.apache.commons.io.FileUtils;

import java.io.File;
import java.io.IOException;

public class WriteToFileExample {
    public static void main(String[] args) {
        try {
            // Here we'll write our data into a file called
            // output.txt; this is the output.
            File file = new File("output.txt");
            // We'll write the string below into the file
            String data = "Learn Java by Examples";

            // To write a file called the writeStringToFile
            // method which requires you to pass the file and
            // the data to be written.
            FileUtils.writeStringToFile(file, data, "UTF-8");
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

Maven Dependencies

<dependency>
    <groupId>commons-io</groupId>
    <artifactId>commons-io</artifactId>
    <version>2.14.0</version>
</dependency>

Maven Central

How do I read text file content line by line to a List of Strings using Commons IO?

By I Wayan Saryada in Apache Commons, Commons IO 2 Comments

The following example show how to use the Apache Commons IO library to read a text file line by line to a List of String. In the code snippet below we will read the contents of a file called sample.txt using FileUtils class. We use FileUtils.readLines() method to read the contents line by line and return the result as a List of Strings.

package org.kodejava.commons.io;

import org.apache.commons.io.FileUtils;

import java.io.File;
import java.io.IOException;
import java.util.List;

public class ReadFileToListSample {
    public static void main(String[] args) {
        // Create a file object of sample.txt
        File file = new File("README.md");

        try {
            List<String> contents = FileUtils.readLines(file, "UTF-8");

            // Iterate the result to print each line of the file.
            for (String line : contents) {
                System.out.println(line);
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

Maven Dependencies

<dependency>
    <groupId>commons-io</groupId>
    <artifactId>commons-io</artifactId>
    <version>2.14.0</version>
</dependency>

Maven Central

How do I read file contents to string using Commons IO?

By I Wayan Saryada in Apache Commons, Commons IO 0 Comment

In this example we use FileUtils class from Apache Commons IO to read the content of a file. FileUtils have two static methods called readFileToString(File) and readFileToString(File, String) that we can use.

An example to read file contents and return the result as a string can be seen below.

package org.kodejava.commons.io;

import org.apache.commons.io.FileUtils;

import java.io.File;
import java.io.IOException;

public class ReadFileToStringSample {
    public static void main(String[] args) {
        // Here we create an instance of File for sample.txt file.
        File file = new File("sample.txt");

        try {
            // Read the entire contents of sample.txt
            String content = FileUtils.readFileToString(file, "UTF-8");
            System.out.println("File content: " + content);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

Maven Dependencies

<dependency>
    <groupId>commons-io</groupId>
    <artifactId>commons-io</artifactId>
    <version>2.14.0</version>
</dependency>

Maven Central

How do I use Java NIO to copy file?

By I Wayan Saryada in Core API, IO 0 Comment

The following code snippet show you how to copy a file using the NIO API. The NIO (New IO) API is in the java.nio.* package. It requires at least Java 1.4 because the API was first included in this version. The JAVA NIO is a block based IO processing, instead of a stream based IO which is the old version IO processing in Java.

package org.kodejava.io;

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.nio.channels.FileChannel;
import java.nio.ByteBuffer;

public class CopyFileExample {
    public static void main(String[] args) throws Exception {
        String source = "medical-report.txt";
        String destination = "medical-report-final.txt";

        FileInputStream fis = new FileInputStream(source);
        FileOutputStream fos = new FileOutputStream(destination);

        FileChannel inputChannel = fis.getChannel();
        FileChannel outputChannel = fos.getChannel();

        // Create a buffer with 1024 size for buffering data
        // while copying from source file to destination file.
        // To create the buffer here we used a static method
        // ByteBuffer.allocate()
        ByteBuffer buffer = ByteBuffer.allocate(1024);

        // Here we start to read the source file and write it
        // to the destination file. We repeat this process
        // until the read method of input stream channel return
        // nothing (-1).
        while (true) {
            // Read a block of data and put it in the buffer
            int read = inputChannel.read(buffer);

            // Did we reach the end of the channel? if yes
            // jump out the while-loop
            if (read == -1) {
                break;
            }

            // flip the buffer
            buffer.flip();

            // write to the destination channel and clear the buffer.
            outputChannel.write(buffer);
            buffer.clear();
        }
    }
}