How do I get free space of a drive or volume?

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

The getFreeSpaceKb(String path) method in the FileSystemUtils class can help you to calculate the free space of a drive or volume in kilobytes.

Beside using commons-io solution, you can use the File.getFreeSpace() method call provided in the Java 1.6 API. You can find an example of it in the following link: How do I get total space and free space of my disk?.

package org.kodejava.commons.io;

import org.apache.commons.io.FileSystemUtils;
import org.apache.commons.io.FileUtils;

import java.io.IOException;

public class DiskFreeSpace {
    public static void main(String[] args) {
        try {
            String path = "F:/Temp";
            long freeSpaceKB = FileSystemUtils.freeSpaceKb(path);
            long freeSpaceMB = freeSpaceKB / FileUtils.ONE_KB;
            long freeSpaceGB = freeSpaceKB / FileUtils.ONE_MB;

            System.out.println("Size of " + path + " = " + freeSpaceKB + " KB");
            System.out.println("Size of " + path + " = " + freeSpaceMB + " MB");
            System.out.println("Size of " + path + " = " + freeSpaceGB + " GB");
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

An example result of the code above is:

Size of F:/Temp = 323413052 KB
Size of F:/Temp = 315833 MB
Size of F:/Temp = 308 GB

Maven Dependencies

<dependency>
    <groupId>commons-io</groupId>
    <artifactId>commons-io</artifactId>
    <version>2.16.1</version>
</dependency>

Maven Central

How do I get printer or print service name?

By I Wayan Saryada in Core API, Print Service 1 Comment

This example show you how to get the printer or print service installed on your machine. To get the installed services we can use PrinterJob.lookupPrintServices() method call. This method return an array of PrintService objects. After that call PrintService.getName() method to get the print service name.

package org.kodejava.print;

import javax.print.PrintService;
import java.awt.print.PrinterJob;

public class PrinterName {
    public static void main(String[] args) {
        // Lookup for the available print services.
        PrintService[] printServices = PrinterJob.lookupPrintServices();

        // Iterates the print services and print out its name.
        for (PrintService printService : printServices) {
            String name = printService.getName();
            System.out.println("Name = " + name);
        }
    }
}

The program will print the installed print service on your machine.

Name = OneNote for Windows 10
Name = OneNote (Desktop)
Name = Microsoft XPS Document Writer
Name = Microsoft Print to PDF
Name = HP LaserJet P1005
Name = Fax

How do I clear a buffer using compact() method?

By I Wayan Saryada in Core API, IO 0 Comment

If you want to clear a buffer, but you want to keep the unread data in the buffer then you need to use the compact() method of the buffer. The compact() method will copy the unread data to the beginning of the buffer and set the position right after the unread data. The limit itself still have the value equals to the buffer capacity. The buffer will be ready to be written again without overwriting the unread data.

package org.kodejava.io;

import java.nio.CharBuffer;

public class BufferCompact {
    public static void main(String[] args) throws Exception {
        CharBuffer buffer = CharBuffer.allocate(64);
        buffer.put("Let's write some Java code! ");

        System.out.println("Position: " + buffer.position());
        System.out.println("Limit   : " + buffer.limit());

        // Read 10 chars from the buffer.
        buffer.flip();
        for (int i = 0; i < 10; i++) {
            System.out.print(buffer.get());
        }
        System.out.println();

        System.out.println("Position: " + buffer.position());
        System.out.println("Limit   : " + buffer.limit());

        // clear the buffer using compact() method.
        buffer.compact();
        System.out.println("Position: " + buffer.position());
        System.out.println("Limit   : " + buffer.limit());

        // Write and read some more data.
        buffer.put("Add some more data.");

        buffer.flip();
        while (buffer.hasRemaining()) {
            System.out.print(buffer.get());
        }
    }
}

The output of the code snippet above is:

Position: 28
Limit   : 64
Let's writ
Position: 10
Limit   : 28
Position: 18
Limit   : 64
e some Java code! Add some more data.

How do I clear a buffer using clear() method?

By I Wayan Saryada in Core API, IO 0 Comment

The code below show you how to clear a buffer using the clear() method call. The clear method call set the position in the buffer to 0 and limit to the capacity of the buffer.

We usually call the clear() method after we read the entire content of a buffer and clear it for ready to be written again. The clear() method is actually not clearing the data in the buffer. It is only clear the marker where you can write the data in the buffer and the unread data will be forgotten.

package org.kodejava.io;

import java.nio.LongBuffer;

public class BufferClear {
    public static void main(String[] args) {
        // Allocates a new LongBuffer.
        LongBuffer buffer = LongBuffer.allocate(64);

        // Write the long array into the buffer.
        buffer.put(new long[]{10, 20, 30, 40, 50, 60, 70, 80});
        System.out.println("Position: " + buffer.position());
        System.out.println("Limit   : " + buffer.limit());

        buffer.flip();
        while (buffer.hasRemaining()) {
            System.out.println(buffer.get());
        }

        // clear() method set the position to zero and limit
        // to the capacity of the buffer.
        buffer.clear();
        System.out.println("Position: " + buffer.position());
        System.out.println("Limit   : " + buffer.limit());
    }
}

The output of the code snippet:

Position: 8
Limit   : 64
10
20
30
40
50
60
70
80
Position: 0
Limit   : 64

How do I get signum function of a number?

By I Wayan Saryada in Core API, Math 0 Comment

The code below show you how to get the signum function of a number using the Math.signum() static method call. This method extracts the sign of a real number. If you have a number of x, the signum function of x is -1 if x < 0; 0 if x = 0 and 1 if x > 0.

package org.kodejava.math;

public class SignumExample {

    public static void main(String[] args) {
        Double zero = 0.0D;
        Double negative = -25.0D;
        Double positive = 15.0D;

        // Get the signum function of value of a number.
        // It returns:
        // * 0 if the value is zero.
        // * 1.0 if value is greater than zero.
        // * -1.0 if value is less than zero.
        double sign1 = Math.signum(zero);
        double sign2 = Math.signum(negative);
        double sign3 = Math.signum(positive);

        // For floating-point value
        float sign4 = Math.signum(zero.floatValue());
        float sign5 = Math.signum(negative.floatValue());
        float sign6 = Math.signum(positive.floatValue());

        System.out.println("In double:");
        System.out.println("Signum of " + zero + " is " + sign1);
        System.out.println("Signum of " + negative + " is " + sign2);
        System.out.println("Signum of " + positive + " is " + sign3);

        System.out.println("In float:");
        System.out.println("Signum of " + zero + " is " + sign4);
        System.out.println("Signum of " + negative + " is " + sign5);
        System.out.println("Signum of " + positive + " is " + sign6);
    }
}

Here is the output of the program:

In double:
Signum of 0.0 is 0.0
Signum of -25.0 is -1.0
Signum of 15.0 is 1.0
In float:
Signum of 0.0 is 0.0
Signum of -25.0 is -1.0
Signum of 15.0 is 1.0