How do I clone an object?

By Wayan in Basic, Core API 0 Comment

To enable our object to be cloned we need to override Object class clone method. We can also add a java.lang.Cloneable interface to our class, this interface is an empty interface. When we call the clone() method we need the add a try-catch block to catch the CloneNotSupportedException. This exception will be thrown if we tried to clone an object that doesn’t suppose to be cloned.

Calling the clone() method does a stateful, shallow copy down inside the Java Virtual Machine (JVM). It creates a new object and copies all the fields from the old object into the newly created object.

package org.kodejava.basic;

public class CloneDemo implements Cloneable {
    private int number;
    private transient int data;

    @Override
    protected Object clone() throws CloneNotSupportedException {
        return super.clone();
    }

    public static void main(String[] args) {
        CloneDemo clone = new CloneDemo();
        clone.number = 5;
        clone.data = 1000;

        try {
            // Create a clone of CloneDemo object. When we change the value of
            // number and data field in the cloned object it won't affect the
            // original object.
            CloneDemo objectClone = (CloneDemo) clone.clone();
            objectClone.number = 10;
            objectClone.data = 5000;

            System.out.println("cloned object = " + objectClone);
            System.out.println("origin object = " + clone);
        } catch (CloneNotSupportedException e) {
            e.printStackTrace();
        }
    }

    public String toString() {
        return "[number = " + number + "; data = " + data + "]";
    }
}

How do I decode a Base64 encoded binary?

By Wayan in Apache Commons, Commons Codec 0 Comment 
package org.kodejava.commons.codec;

import org.apache.commons.codec.binary.Base64;

import java.util.Arrays;

public class Base64Decode {
    public static void main(String[] args) {
        String hello = "SGVsbG8gV29ybGQ=";

        // Decode a previously encoded string using decodeBase64 method and
        // passing the byte[] of the encoded string.
        byte[] decoded = Base64.decodeBase64(hello.getBytes());

        // Print the decoded array
        System.out.println(Arrays.toString(decoded));

        // Convert the decoded byte[] back to the original string and print
        // the result.
        String decodedString = new String(decoded);
        System.out.println(hello + " = " + decodedString);
    }
}

The result of our code is:

[72, 101, 108, 108, 111, 32, 87, 111, 114, 108, 100]
SGVsbG8gV29ybGQ= = Hello World

Maven Dependencies

<dependency>
    <groupId>commons-codec</groupId>
    <artifactId>commons-codec</artifactId>
    <version>1.16.0</version>
</dependency>

Maven Central

How do I encode binary data as Base64 string?

By Wayan in Apache Commons, Commons Codec 0 Comment 
package org.kodejava.commons.codec;

import org.apache.commons.codec.binary.Base64;

import java.util.Arrays;

public class Base64Encode {
    public static void main(String[] args) {
        String hello = "Hello World";

        // The encodeBase64 method take a byte[] as the parameter. The byte[]
        // can be from a simple string like in this example, or it can be from
        // an image file data.
        byte[] encoded = Base64.encodeBase64(hello.getBytes());

        // Print the encoded byte array
        System.out.println(Arrays.toString(encoded));

        // Print the encoded string
        String encodedString = new String(encoded);
        System.out.println(hello + " = " + encodedString);
    }
}

The result of our program:

[83, 71, 86, 115, 98, 71, 56, 103, 86, 50, 57, 121, 98, 71, 81, 61]
Hello World = SGVsbG8gV29ybGQ=

Maven Dependencies

<dependency>
    <groupId>commons-codec</groupId>
    <artifactId>commons-codec</artifactId>
    <version>1.16.0</version>
</dependency>

Maven Central

How do I convert java.util.Set into Array?

By Wayan in Core API, Util Package 0 Comment 
package org.kodejava.util;

import java.util.*;

public class SetToArray {
    public static void main(String[] args) {
        // Create a java.util.Set object and add some integers into the Set.
        Set<Integer> numberSet = new HashSet<>();
        numberSet.add(1);
        numberSet.add(2);
        numberSet.add(3);
        numberSet.add(5);
        numberSet.add(8);

        // Converting a java.util.Set into an array can be done by creating a
        // java.util.List object from the Set and then convert it into an array
        // by calling the toArray() method on the list object.
        List<Integer> numberList = new ArrayList<>(numberSet);
        Integer[] numbers = numberList.toArray(new Integer[0]);

        // Display the content of numbers array.
        for (int i = 0; i < numbers.length; i++) {
            Integer number = numbers[i];
            System.out.print(number + (i < numbers.length - 1 ? ", " : "\n"));
        }

        // Display the content of numbers array using the for-each loop.
        for (Integer number : numbers) {
            System.out.print(number + ", ");
        }
    }
}

How do I convert Set into List?

By Wayan in Core API, Util Package 0 Comment

The code below gives you an example of converting a java.util.Set into a java.util.List. It has simply done by creating a new instance of List and pass the Set as the argument of the constructor.

package org.kodejava.util;

import java.util.*;

public class SetToList {
    public static void main(String[] args) {
        // Create a Set and add some objects into the Set.
        Set<Object> set = new HashSet<>();
        set.add("A");
        set.add(10L);
        set.add(new Date());

        // Convert the Set to a List can be done by passing the Set instance into
        // the constructor of a List implementation class such as ArrayList.
        List<Object> list = new ArrayList<>(set);
        for (Object o : list) {
            System.out.println("Object = " + o);
        }
    }
}

The output of the code snippet are:

Object = A
Object = 10
Object = Mon Oct 04 20:20:26 CST 2021