How do I capitalize each word in a string?

By Wayan in Apache Commons, Commons Text 0 Comment

This example show you how to capitalize a string. We use methods from WordUtils class provided by the Apache commons-text;. We can use the WordUtils.capitalize(str) or WordUtils.capitalizeFully(str).

Let’s see an example below:

package org.kodejava.commons.text;

import org.apache.commons.text.WordUtils;

public class WordCapitalize {
    public static void main(String[] args) {
        // Capitalizes all the whitespace separated words in a string,
        // only the first letter of each word is capitalized.
        String str = WordUtils.capitalize(
                "The quick brown fox JUMPS OVER the lazy dog.");
        System.out.println("str = " + str);

        // Capitalizes all the whitespace separated words in a string
        // and the rest string to lowercase.
        str = WordUtils.capitalizeFully(
                "The quick brown fox JUMPS OVER the lazy dog.");
        System.out.println("str = " + str);
    }
}

And here are the result of the program:

str = The Quick Brown Fox JUMPS OVER The Lazy Dog.
str = The Quick Brown Fox Jumps Over The Lazy Dog.

Maven Dependencies

<dependency>
    <groupId>org.apache.commons</groupId>
    <artifactId>commons-text</artifactId>
    <version>1.12.0</version>
</dependency>

Maven Central

How do I create a thread synchronized block?

By Wayan in Core API, Lang Package 0 Comment

The objective of thread synchronization is to ensure that when several threads want access to a single resource, only one thread can access it at any given time.

You can manage synchronization of your program at method level (synchronized method) or at block level (synchronized block). To make a block of code synchronized you can use the synchronized keyword.

The example below show how you can use the synchronized keyword.

  • Incrementor class
package org.kodejava.lang;

public class Incrementor {
    private int count;

    // A synchronized method example.
    public synchronized void increment(int value) {
        count += value;
        System.out.println(Thread.currentThread().getName() +
                ": inc >>> " + count);
    }

    public void decrement(int value) {
        // A synchronized block example the use the current object instance
        // as the monitor object.
        synchronized (this) {
            count -= value;
            System.out.println(Thread.currentThread().getName() +
                    ": dec >>> " + count);
        }
    }
}
  • IncrementThread class
package org.kodejava.lang;

public class IncrementThread implements Runnable {
    private final Incrementor incrementor;

    public IncrementThread(Incrementor incrementor) {
        this.incrementor = incrementor;
    }

    public void run() {
        for (int i = 1; i <= 5; i++) {
            incrementor.increment(i * 10);
            incrementor.decrement(i * 2);

            try {
                Thread.sleep(1000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }
}
  • IncrementorDemo class
package org.kodejava.lang;

public class IncrementorDemo {
    public static void main(String[] args) {
        Incrementor incrementor = new Incrementor();

        Thread t1 = new Thread(new IncrementThread(incrementor), "T1");
        Thread t2 = new Thread(new IncrementThread(incrementor), "T2");

        t1.start();
        t2.start();
    }
}

Here an example result printed by the program:

T1: inc >>> 10
T1: dec >>> 8
T2: inc >>> 18
T2: dec >>> 16
T1: inc >>> 36
T1: dec >>> 32
T2: inc >>> 52
T2: dec >>> 48
T1: inc >>> 78
T1: dec >>> 72
T2: inc >>> 102
T2: dec >>> 96
T1: inc >>> 136
T1: dec >>> 128
T2: inc >>> 168
T2: dec >>> 160
T1: inc >>> 210
T1: dec >>> 200
T2: inc >>> 250
T2: dec >>> 240

How do I get the component type of array?

By Wayan in Reflection 0 Comment

The Class.getComponentType() method call returns the Class representing the component type of array. If this class does not represent an array class this method returns null reference instead.

package org.kodejava.lang.reflect;

public class ComponentTypeDemo {
    public static void main(String[] args) {
        String[] words = {"and", "the"};
        int[][] matrix = {{1, 1}, {2, 1}};
        Double number = 10.0;

        Class<?> clazz = words.getClass();
        Class<?> cls = matrix.getClass();
        Class<?> clz = number.getClass();

        // Gets the type of array component.
        Class<?> type = clazz.getComponentType();
        System.out.println("Words type: " +
                type.getCanonicalName());

        // Gets the type of array component.
        Class<?> matrixType = cls.getComponentType();
        System.out.println("Matrix type: " +
                matrixType.getCanonicalName());

        // It will return null if the class doesn't represent
        // an array.
        Class<?> numberType = clz.getComponentType();
        if (numberType != null) {
            System.out.println("Number type: " +
                    numberType.getCanonicalName());
        } else {
            System.out.println(number.getClass().getName() +
                    " class is not an array");
        }
    }
}

This program print the following output:

Words type: java.lang.String
Matrix type: int[]
java.lang.Double class is not an array

How do I determine if a class object represents an array class?

By Wayan in Reflection 0 Comment

For checking if a class object is representing an array class we can use the isArray() method call of the Class object. This method returns true if the checked object represents an array class and false otherwise.

package org.kodejava.lang.reflect;

public class IsArrayDemo {
    public static void main(String[] args) {
        int[][] matrix = {{1, 1}, {2, 1}};
        Class<?> clazz = matrix.getClass();

        // Check if the class object represents an array class
        if (clazz.isArray()) {
            System.out.println(clazz.getSimpleName() +
                    " is an array class.");
        } else {
            System.out.println(clazz.getSimpleName() +
                    " is not an array class.");
        }
    }
}

How do I check if a class represent a primitive type?

By Wayan in Reflection 0 Comment

Java uses class objects to represent all eight primitive types. A class object that represents a primitive type can be identified using the isPrimitive() method call. void is not a type in Java, but the isPrimitive() method returns true for void.class.

package org.kodejava.lang.reflect;

public class IsPrimitiveDemo {
    public static void main(String[] args) {
        IsPrimitiveDemo.get(int.class);
        IsPrimitiveDemo.get(String.class);
        IsPrimitiveDemo.get(double.class);
        IsPrimitiveDemo.get(void.class);
    }

    private static void get(Class<?> clazz) {
        if (clazz.isPrimitive()) {
            System.out.println(clazz.getName() +
                    " is a primitive type.");
        } else {
            System.out.println(clazz.getName() +
                    " is not a primitive type.");
        }
    }
}

Here is the result of the program:

int is a primitive type.
java.lang.String is not a primitive type.
double is a primitive type.
void is a primitive type.