How do I create and delete a file in JDK 7?

By Wayan in Core API, IO 0 Comment

In this example you’ll learn how to create and delete a file. Using the new Files class helper from the JDK 7 you can create a file using the Files.createFile(Path) method. To delete a file you can use the Files.delete(Path) method.

Before create a file and delete a file we can check to see if the file exists or not using the Files.exists(Path) method. In the code snippet below we’ll create a file when the file is not exist. And we’ll delete the file if the file exists.

package org.kodejava.io;

import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;

public class CreateDeleteFile {
    public static void main(String[] args) {
        try {
            // Create a config.cfg file under D:Temp directory.
            Path path = Paths.get("F:/Temp/config.cfg");
            if (!Files.exists(path)) {
                Files.createFile(path);
            }

            // Delete the path.cfg file specified by the Path.
            if (Files.exists(path)) {
                Files.delete(path);
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

How to recursively list all text files in a directory?

By Wayan in Core API, IO 0 Comment

In this example you’ll learn how to use the Files.walkFileTree() to walk through file tree. This method requires two parameters. The first parameter is the starting file, in this example we’ll start from drive F:/Temp. And the second parameter is the file visitor to invoke for each file. Here we’ll create a file visitor call FindTextFilesVisitor which extend the java.nio.file.SimpleFileVisitor.

To get all the text files (files end with .txt) we override the visitFile() defined by the SimpleFileVisitor. In this method we check if the file ends with .txt extension and print the file name when the extension matches. And we continue to walk the file tree by returning FileVisitResult.CONTINUE.

package org.kodejava.io;

import java.io.IOException;
import java.nio.file.*;
import java.nio.file.attribute.BasicFileAttributes;

public class WalkFileTree {
    public static void main(String[] args) {
        try {
            Path startDir = Paths.get("F:/Temp");
            Files.walkFileTree(startDir, new FindTextFilesVisitor());
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    /**
     * FindTextFilesVisitor.
     */
    static class FindTextFilesVisitor extends SimpleFileVisitor<Path> {
        @Override
        public FileVisitResult visitFile(Path file, BasicFileAttributes attrs) throws IOException {
            if (file.toString().endsWith(".txt")) {
                System.out.println(file.getFileName());
            }
            return FileVisitResult.CONTINUE;
        }
    }
}

Instead of listing files, you can modify the code snippet above for instance use it to delete all the files that ends with .bak. Simply change the extension and replace the print-out statement with a file delete statement in the visitFile() method.

How do I remove redundant elements from a Path?

By Wayan in Core API, IO 0 Comment

To eliminate redundant elements from a Path we can use the Path.normalize() method. For example in the following code snippet. When try accessing the README file in the current directory the . symbol in the Path elements considered to be redundant, we don’t need it. That’s why we normalize the Path.

package org.kodejava.io;

import java.nio.file.Path;
import java.nio.file.Paths;

public class PathNormalize {
    public static void main(String[] args) {
        // The following Path contains a redundant element. The "." which 
        // basically point to the current directory can simply be removed
        // when we are working on the current directory.
        Path path = Paths.get("./README.md");
        System.out.println("Path = " + path);

        // Removes redundant name elements from the path.
        path = path.normalize();
        System.out.println("Path = " + path);
    }
}

How to get some information about Path object?

By Wayan in Core API, IO 0 Comment

The java.nio.Path provides some methods to obtain information about the Path. For example, you can get information about the file name, the parent and the root path. For these you can call the getFileName(), getParent() and getRoot() method respectively.

You can also get the number of elements that make up this Path using the getNameCount() method. And to get the sub-path you can use the subpath() method and specify the starting and ending indexes. The code snippet below demonstrate to you how to get this information.

package org.kodejava.io;

import java.nio.file.Path;
import java.nio.file.Paths;

public class PathInfoExample {
    public static void main(String[] args) {
        // Create a Path for Windows notepad program.
        Path notepad = Paths.get("C:/Windows/System32/notepad.exe");

        // Get some information about the Path object.
        System.out.printf("File name         : %1$s%n", notepad.getFileName());
        System.out.printf("Name count        : %1$s%n", notepad.getNameCount());
        System.out.printf("Parent path       : %1$s%n", notepad.getParent());
        System.out.printf("Root path         : %1$s%n", notepad.getRoot());
        System.out.printf("Sub path from root: %1$s%n", notepad.subpath(0, 2));
    }
}

This code will print something like:

File name         : notepad.exe
Name count        : 3
Parent path       : C:\Windows\System32
Root path         : C:\
Sub path from root: Windows\System32

How do I create a java.nio.Path?

By Wayan in Core API, IO 0 Comment

The following code snippet show you how to create a Path. A Path (java.nio.Path) in an interface that represent a location in a file system, such as C:/Windows/System32 or /usr/bin.

To create a Path we can use the java.nio.Paths.get(String first, String... more) methods. Below you can see how to create a Path by passing only the first string and by passing a first string plus some varargs string.

package org.kodejava.io;

import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;

public class PathCreate {
    public static void main(String[] args) {
        // Create a Path that represents Windows installation location.
        Path windows = Paths.get("C:/Windows");

        // Check to see if the path represent a directory.
        if (Files.isDirectory(windows)) {
            // do something
        }

        // Create a Path that represent Windows programs installation location.
        Path programFiles = Paths.get("C:/Program Files");
        Files.isDirectory(programFiles);

        // Create a Path that represent the notepad.exe program
        Path notepad = Paths.get("C:/Windows", "System32", "notepad.exe");

        // Check to see if the path represent an executable file.
        if (Files.isExecutable(notepad)) {
            // do something
        }
    }
}

How do I copy a file in JDK 7?

By Wayan in Core API, IO 0 Comment

In this example you’ll see how to copy a file using the new API provided in the JDK 7. The first step is to define the source and the target of the file to be copied. For this we can use the Path class. To create an instance of Path we use the Paths.get() method by passing the path information as the arguments.

Next we can configure the file copy operation option. For this we can define it as an array of CopyOtion. We can use copy option such as StandardCopyOption.REPLACE_EXISTING and StandardCopyOption.COPY_ATTRIBUTES.

Finally, to copy the file we use the Files.copy() method. We give three arguments to this method, they are the source file, the target file and the copy options information.

Let’s see the code snippet below:

package org.kodejava.io;

import java.io.IOException;
import java.nio.file.*;

public class NioFileCopyDemo {
    public static void main(String[] args) {
        // Define the source and target of the file to be copied.
        Path source = Paths.get("D:/resources/data.txt");
        Path target = Paths.get("D:/resources/data.bak");

        // Define the options used in the file copy process.
        CopyOption[] options = new CopyOption[]{
                StandardCopyOption.REPLACE_EXISTING,
                StandardCopyOption.COPY_ATTRIBUTES
        };

        try {
            // Copy file from source to target using the defined 
            // configuration.
            Files.copy(source, target, options);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

How do I use the DosFileAttributes class?

By Wayan in Core API, IO 8 Comments

This example show you how to use the DosFileAttributes class to get file attribute that support DOS file system. This class extends the BasicFileAttributes class. Using the DosFileAttributes class we can read file attributes using isArchive(), isHidden(), isReadOnly() and isSystem() methods.

Let’s see the code snippet below:

package org.kodejava.io;

import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.nio.file.attribute.DosFileAttributes;

public class DosFileAttributeExample {
    public static void main(String[] args) throws Exception {
        String path = "D:/resources/data.txt";

        Path file = Paths.get(path);
        DosFileAttributes attr = Files.readAttributes(file, DosFileAttributes.class);

        System.out.println("isArchive()  = " + attr.isArchive());
        System.out.println("isHidden()   = " + attr.isHidden());
        System.out.println("isReadOnly() = " + attr.isReadOnly());
        System.out.println("isSystem()   = " + attr.isSystem());
    }
}

The output of the code snippet:

isArchive()  = true
isHidden()   = false
isReadOnly() = false
isSystem()   = false

How do I set the value of file attributes?

By Wayan in Core API, IO 0 Comment

This code snippet show you an example on how to set the value of file attributes. Here we will set the DosFileAttributes. To set the value of file attributes we use the Files.setAttributes() method. To set DosFileAttributes we can use the following attributes: "dos:archive", "dos:hidden", "dos:readonly" and "dos:system".

For details let’s see the code snippet below:

package org.kodejava.io;

import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.nio.file.attribute.DosFileAttributes;

public class UpdateDosFileAttributesExample {
    public static void main(String[] args) throws Exception {
        String path = "D:/resources/data.txt";
        Path file = Paths.get(path);

        // Get current Dos file attributes and print it.
        DosFileAttributes attr = Files.readAttributes(file, DosFileAttributes.class);
        printAttributes(attr);

        // Set a new file attributes.
        Files.setAttribute(file, "dos:archive", false);
        Files.setAttribute(file, "dos:hidden", false);
        Files.setAttribute(file, "dos:readonly", false);
        Files.setAttribute(file, "dos:system", false);

        // Read the newly set file attributes and print it.
        attr = Files.readAttributes(file, DosFileAttributes.class);
        printAttributes(attr);
    }

    /**
     * Print the DosFileAttributes information.
     *
     * @param attr DosFileAttributes.
     */
    private static void printAttributes(DosFileAttributes attr) {
        System.out.println("isArchive()  = " + attr.isArchive());
        System.out.println("isHidden()   = " + attr.isHidden());
        System.out.println("isReadOnly() = " + attr.isReadOnly());
        System.out.println("isSystem()   = " + attr.isSystem());
        System.out.println("----------------------------------------");
    }
}

The output of the code snippet:

isArchive()  = true
isHidden()   = true
isReadOnly() = true
isSystem()   = true
----------------------------------------
isArchive()  = false
isHidden()   = false
isReadOnly() = false
isSystem()   = false
----------------------------------------

How do I write a text file in JDK 7?

By Wayan in Core API, IO 0 Comment

In JDK 7 we can write all lines from a List of String into a file using the Files.write() method. We need to provide the Path of the file we want to write to, the List of strings and the charsets. Each line is a char sequence and is written to the file in sequence with each line terminated by the platform’s line separator.

Let’s see the code snippet below:

package org.kodejava.io;

import java.nio.charset.StandardCharsets;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.ArrayList;
import java.util.List;

public class WriteTextFile {
    public static void main(String[] args) {
        Path file = Paths.get("D:/resources/data.txt");

        List<String> lines = new ArrayList<>();
        lines.add("Lorem Ipsum is simply dummy text of the printing ");
        lines.add("and typesetting industry. Lorem Ipsum has been the ");
        lines.add("industry's standard dummy text ever since the 1500s, ");
        lines.add("when an unknown printer took a galley of type and ");
        lines.add("scrambled it to make a type specimen book.");

        try {
            // Write lines of text to a file.
            Files.write(file, lines, StandardCharsets.UTF_8);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

This code snippet will create a file called data.txt under the resources folder. Please make sure that this folder is existed before you tried to run the code.

How do I get file basic attributes?

By Wayan in Core API, IO 2 Comments

This example you’ll learn how to get file’s basic attributes. Basic file attributes are attributes that are common to many file systems and consist of mandatory and optional file attributes as defined by the BasicFileAttributes interface.

The file’s basic attributes include file’s date time information such as the creation time, last access time, last modified time. You can also check whether the file is a directory, a regular file, a symbolic link or something else. You can also get the size of the file.

Let’s see the code snippet below:

package org.kodejava.io;

import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.nio.file.attribute.BasicFileAttributes;

public class FileAttributesDemo {
    public static void main(String[] args) throws Exception {
        String path = "D:/resources/data.txt";

        Path file = Paths.get(path);
        BasicFileAttributes attr = Files.readAttributes(file, BasicFileAttributes.class);
        System.out.println("creationTime     = " + attr.creationTime());
        System.out.println("lastAccessTime   = " + attr.lastAccessTime());
        System.out.println("lastModifiedTime = " + attr.lastModifiedTime());

        System.out.println("isDirectory      = " + attr.isDirectory());
        System.out.println("isOther          = " + attr.isOther());
        System.out.println("isRegularFile    = " + attr.isRegularFile());
        System.out.println("isSymbolicLink   = " + attr.isSymbolicLink());
        System.out.println("size             = " + attr.size());
    }
}

The output of the code snippet:

creationTime     = 2021-05-05T17:09:09.0628061Z
lastAccessTime   = 2021-05-05T17:09:09.0628061Z
lastModifiedTime = 2021-11-04T00:11:43.279Z
isDirectory      = false
isOther          = false
isRegularFile    = true
isSymbolicLink   = false
size             = 0