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

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

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.example.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 = "/Users/wayan";
            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 /Users/wayan = 70583428 KB
Size of /Users/wayan = 68929 MB
Size of /Users/wayan = 67 GB

Maven Dependencies

<!-- http://repo1.maven.org/maven2/commons-io/commons-io/2.6/commons-io-2.6.jar -->
<dependency>
    <groupId>commons-io</groupId>
    <artifactId>commons-io</artifactId>
    <version>2.6</version>
</dependency>

How do I generate a random alpha-numeric string?

The code below show you how to use the Apache Commons-Lang RandomStringUtils class to generate some random string data.

package org.kodejava.example.commons.lang;

import org.apache.commons.lang3.RandomStringUtils;

public class RandomStringUtilsDemo {
    public static void main(String[] args) {
        // Creates a 64 chars length random string of number.
        String result = RandomStringUtils.random(64, false, true);
        System.out.println("random = " + result);

        // Creates a 64 chars length of random alphabetic string.
        result = RandomStringUtils.randomAlphabetic(64);
        System.out.println("random = " + result);

        // Creates a 32 chars length of random ascii string.
        result = RandomStringUtils.randomAscii(32);
        System.out.println("random = " + result);

        // Creates a 32 chars length of string from the defined array of
        // characters including numeric and alphabetic characters.
        result = RandomStringUtils.random(32, 0, 20, true, true, "qw32rfHIJk9iQ8Ud7h0X".toCharArray());
        System.out.println("random = " + result);
    }
}

The example of our program result are:

random = 2807246146525875794860509906530938229981588250176397328237925194
random = SWMZqKHTfWkJOIMMliShJKSGHIiBcQJxukwLQxazxZymuSCyLVCDTYsFehrIPwRr
random = e}&"_8Ek%F'7&_T8\G~YPEG2#N-^_|xw
random = 0IHI8dIk2Xf0fJX0HqJr78dq7w92Qd0U

Maven Dependencies

<!-- https://search.maven.org/remotecontent?filepath=org/apache/commons/commons-lang3/3.9/commons-lang3-3.9.jar -->
<dependency>
    <groupId>org.apache.commons</groupId>
    <artifactId>commons-lang3</artifactId>
    <version>3.9</version>
</dependency>

Maven Central

How do I read a file into byte array using Commons IO?

The following example shows you how to read file contents into byte array. We use the IOUtils class of the commons-io library.

package org.kodejava.example.commons.io;

import org.apache.commons.io.IOUtils;

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;

public class FileToByteArray {
    public static void main(String[] args) {
        File file = new File("data.txt");
        try {
            InputStream is = new FileInputStream(file);
            byte[] bytes = IOUtils.toByteArray(is);

            System.out.println("Byte array size: " + bytes.length);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

Maven Dependencies

<!-- http://repo1.maven.org/maven2/commons-io/commons-io/2.6/commons-io-2.6.jar -->
<dependency>
    <groupId>commons-io</groupId>
    <artifactId>commons-io</artifactId>
    <version>2.6</version>
</dependency>

How do I get the content of an InputStream as a String?

We can use the code below to convert the content of an InputStream into a String. At first we use FileInputStream create to a connection to a file that going to be read. IOUtils.toString(InputStream input, String encoding) method gets the content of the InputStream and returns a string representation of it. In the end we need to close the InputStream in a finally block.

package org.kodejava.example.commons.io;

import org.apache.commons.io.IOUtils;

import java.io.InputStream;
import java.io.FileInputStream;
import java.io.File;

public class InputStreamToString {
    public static void main(String[] args) throws Exception {
        // Create an input stream for reading data.txt file content.
        try (InputStream is = new FileInputStream(new File("data.txt"))) {
            // Get the content of an input stream as a string using UTF-8
            // as the character encoding.
            String contents = IOUtils.toString(is, "UTF-8");
            System.out.println(contents);
        }
    }
}

Maven Dependencies

<!-- http://repo1.maven.org/maven2/commons-io/commons-io/2.6/commons-io-2.6.jar -->
<dependency>
    <groupId>commons-io</groupId>
    <artifactId>commons-io</artifactId>
    <version>2.6</version>
</dependency>

How do I set mapped property value of a bean?

This example demonstrate how to use PropertyUtils.setMappedProperty() method to modify a Map typed property value of a bean. To set the property we need to pass bean instance, property name, map key and map value to PropertyUtils.setMappedProperty() method.

package org.kodejava.example.commons.beanutils;

import org.apache.commons.beanutils.PropertyUtils;

import java.util.HashMap;
import java.util.Map;

public class PropertySetMappedExample {

    public static void main(String[] args) {
        // Create an instance of Recording bean.
        Recording recording = new Recording();
        recording.setId(1L);
        recording.setTitle("Introduction");

        // Create a map to hold recording tracks.
        Map<String, Track> tracks = new HashMap<>();
        tracks.put("track-one", new Track());
        tracks.put("track-two", new Track());
        tracks.put("track-three", new Track());
        recording.setMapTracks(tracks);

        try {
            // We add another tracks to the recording track using
            // a PropertyUtils.setMappedProperty() method.
            PropertyUtils.setMappedProperty(recording, "mapTracks", "track-four", new Track());
            PropertyUtils.setMappedProperty(recording, "mapTracks", "track-five", new Track());
        } catch (Exception e) {
            e.printStackTrace();
        }

        tracks = recording.getMapTracks();
        System.out.println("New Track Numbers: " + tracks.size());
        for (String key : tracks.keySet()) {
            System.out.println(key + " = " + tracks.get(key));
        }
    }
}

Maven Dependencies

<!-- https://search.maven.org/remotecontent?filepath=commons-beanutils/commons-beanutils/1.9.3/commons-beanutils-1.9.3.jar -->
<dependency>
    <groupId>commons-beanutils</groupId>
    <artifactId>commons-beanutils</artifactId>
    <version>1.9.3</version>
</dependency>

How do I set indexed property value of a bean?

In this example we display how to set the value of an indexed property. In the code below we modified the value of an array type. We’ll change the second colors of MyBean‘s colors property.

We do it in the same way as using the PropertyUtils.setSimpleProperty method. For indexed property we use the PropertyUtils.setIndexedProperty method and passes four arguments, they are the instance of bean to be manipulated, the indexed property name, the index to be changes and the finally the new value.

package org.kodejava.example.commons.beanutils;

import org.apache.commons.beanutils.PropertyUtils;

import java.util.Arrays;

public class PropertySetIndexedExample {
    public static void main(String[] args) {
        String[] colors = new String[]{"red", "green", "blue"};

        MyBean myBean = new MyBean();
        myBean.setColors(colors);
        System.out.println("Colors = " + Arrays.toString(myBean.getColors()));

        try {
            PropertyUtils.setIndexedProperty(myBean, "colors", 1, "orange");
        } catch (Exception e) {
            e.printStackTrace();
        }

        System.out.println("Colors = " + Arrays.toString(myBean.getColors()));
    }
}
package org.kodejava.example.commons.beanutils;

public class MyBean {
    private String[] colors;

    public void setColors(String[] colors) {
        this.colors = colors;
    }

    public String[] getColors() {
        return colors;
    }
}

The output of this code is:

Colors = [red, green, blue]
Colors = [red, orange, blue]

Maven Dependencies

<!-- https://search.maven.org/remotecontent?filepath=commons-beanutils/commons-beanutils/1.9.3/commons-beanutils-1.9.3.jar -->
<dependency>
    <groupId>commons-beanutils</groupId>
    <artifactId>commons-beanutils</artifactId>
    <version>1.9.3</version>
</dependency>

How do I set property value of a bean?

The Commons BeanUtils component provides a class called PropertyUtils that supplies method for manipulating a bean such as our Track class below. For this demo we use a Track class that have a property called id, title and duration.

To set the value of a bean we can use the PropertyUtils.setProperty() method. This method ask for the bean instance whose property value to be set, the property name and the value.

package org.kodejava.example.commons.beanutils;

import org.apache.commons.beanutils.PropertyUtils;

public class PropertySetExample {
    public static void main(String[] args) {
        Track track = new Track();
        try {
            PropertyUtils.setProperty(track, "id", 10L);
            PropertyUtils.setProperty(track, "title", "Hey Jude");
            PropertyUtils.setProperty(track, "duration", 180);
        } catch (Exception e) {
            e.printStackTrace();
        }

        System.out.println("Track = " + track);
    }
}
package org.kodejava.example.commons.beanutils;

public class Track {
    private Long id;
    private String title;
    private Integer duration;

    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public String getTitle() {
        return title;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    public Integer getDuration() {
        return duration;
    }

    public void setDuration(Integer duration) {
        this.duration = duration;
    }
}

Some exceptions could be thrown by this method, so we need to handle the IllegalAccessException, InvocationAccessException and NoSuchMethodException. To make the code simple we will just catch it as java.lang.Exception.

These exception could happen if we don’t have access to the property, or the bean’s accessor throws an exception or if the method we tried to manipulate doesn’t exist.

Maven Dependencies

<!-- https://search.maven.org/remotecontent?filepath=commons-beanutils/commons-beanutils/1.9.3/commons-beanutils-1.9.3.jar -->
<dependency>
    <groupId>commons-beanutils</groupId>
    <artifactId>commons-beanutils</artifactId>
    <version>1.9.3</version>
</dependency>

How do I add query string to HttpMethod object?

To send query string information in HTTP GET command you either using passing a simple string or an array of NameValuePair object into the HttpMethod‘s setQueryString() method. We also need to encode the parameter values before passing it to the method.

package org.kodejava.example.commons.httpclient;

import org.apache.commons.httpclient.*;
import org.apache.commons.httpclient.util.URIUtil;
import org.apache.commons.httpclient.methods.GetMethod;

import java.io.IOException;

public class SendingQueryParameter {
    public static void main(String[] args) {
        HttpClient client = new HttpClient();
        HttpMethod method = new GetMethod("http://localhost:8080/hello.jsp");

        try {
            // Set query string information for accessing the page using a
            // simple string information.
            method.setQueryString(URIUtil.encodeQuery("catid=10&page=1"));
            client.executeMethod(method);

            // Other cleaner alternative is to use the NameValuePair object to
            // define the parameters for a HTTP GET method.
            NameValuePair param1 = new NameValuePair("catid", URIUtil.encodeQuery("20"));
            NameValuePair param2 = new NameValuePair("page", URIUtil.encodeQuery("2"));
            NameValuePair[] params = new NameValuePair[] {param1, param2};
            method.setQueryString(params);
            client.executeMethod(method);
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            method.releaseConnection();
        }
    }
}

Maven Dependencies

<!-- http://repo1.maven.org/maven2/commons-httpclient/commons-httpclient/3.1/commons-httpclient-3.1.jar -->
<dependency>
    <groupId>commons-httpclient</groupId>
    <artifactId>commons-httpclient</artifactId>
    <version>3.1</version>
</dependency>

How do I setting a proxy for HttpClient?

In this example you will see how to configure proxy when using the Apache Commons HttpClient library.

package org.kodejava.example.commons.httpclient;

import org.apache.commons.httpclient.Credentials;
import org.apache.commons.httpclient.HostConfiguration;
import org.apache.commons.httpclient.HttpClient;
import org.apache.commons.httpclient.HttpMethod;
import org.apache.commons.httpclient.HttpStatus;
import org.apache.commons.httpclient.UsernamePasswordCredentials;
import org.apache.commons.httpclient.auth.AuthScope;
import org.apache.commons.httpclient.methods.GetMethod;

import java.io.IOException;

public class HttpGetProxy {
    private static final String PROXY_HOST = "proxy.host.com";
    private static final int PROXY_PORT = 8080;

    public static void main(String[] args) {
        HttpClient client = new HttpClient();
        HttpMethod method = new GetMethod("https://kodejava.org");

        HostConfiguration config = client.getHostConfiguration();
        config.setProxy(PROXY_HOST, PROXY_PORT);

        String username = "guest";
        String password = "s3cr3t";
        Credentials credentials = new UsernamePasswordCredentials(username, password);
        AuthScope authScope = new AuthScope(PROXY_HOST, PROXY_PORT);

        client.getState().setProxyCredentials(authScope, credentials);

        try {
            client.executeMethod(method);

            if (method.getStatusCode() == HttpStatus.SC_OK) {
                String response = method.getResponseBodyAsString();
                System.out.println("Response = " + response);
            }
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            method.releaseConnection();
        }
    }
}

Maven Dependencies

<!-- http://repo1.maven.org/maven2/commons-httpclient/commons-httpclient/3.1/commons-httpclient-3.1.jar -->
<dependency>
    <groupId>commons-httpclient</groupId>
    <artifactId>commons-httpclient</artifactId>
    <version>3.1</version>
</dependency>

How do I perform HTTP GET method?

Below is an example using Commons HttpClient library to retrieve information from a website using HTTP GET method. The response will be returned as stream by the HttpMethod.getResponseBodyAsStream() method. If you want something simple you can get the response as string by using the HttpMethod.getResponseBodyAsString() method.

package org.kodejava.example.commons.httpclient;

import org.apache.commons.httpclient.HttpClient;
import org.apache.commons.httpclient.HttpMethod;
import org.apache.commons.httpclient.HttpStatus;
import org.apache.commons.httpclient.methods.GetMethod;

import java.io.*;
import java.nio.charset.StandardCharsets;

public class HttpGetDemo {
    public static void main(String[] args) {
        HttpClient client = new HttpClient();
        HttpMethod method = new GetMethod("https://kodejava.org");

        try {
            client.executeMethod(method);

            if (method.getStatusCode() == HttpStatus.SC_OK) {
                InputStream is = method.getResponseBodyAsStream();

                if (is != null) {
                    Writer writer = new StringWriter();
                    char[] buffer = new char[1024];
                    try {
                        Reader reader = new BufferedReader(new InputStreamReader(is,
                            StandardCharsets.UTF_8));
                        int length;
                        while ((length = reader.read(buffer)) != -1) {
                            writer.write(buffer, 0, length);
                        }
                    } finally {
                        is.close();
                    }
                    System.out.println("Response = " + writer.toString());
                }
            }
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            method.releaseConnection();
        }
    }
}

Maven Dependencies

<!-- http://repo1.maven.org/maven2/commons-httpclient/commons-httpclient/3.1/commons-httpclient-3.1.jar -->
<dependency>
    <groupId>commons-httpclient</groupId>
    <artifactId>commons-httpclient</artifactId>
    <version>3.1</version>
</dependency>