How do I copy char array to string?

By I Wayan Saryada in Core API, Lang Package 0 Comment 
package org.kodejava.lang;

public class CharArrayCopyExample {
    public static void main(String[] args) {
        char[] data = {'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j'};

        // Copy all value in the char array and create a new string out of it.
        String text = String.valueOf(data);
        System.out.println(text);

        // Copy a sub array from the char array and create a new string. The
        // following line will just copy 5 characters starting from array index
        // of 3. If the element copied is outside the array index an
        // IndexOutOfBoundsException will be thrown.
        text = String.copyValueOf(data, 3, 5);
        System.out.println(text);
    }
}

The result:

abcdefghij
defgh

How do I remove leading and trailing white space from string?

By I Wayan Saryada in Core API, Lang Package 0 Comment 
package org.kodejava.lang;

public class TrimStringExample {
    public static void main(String[] args) {
        String text = "     tattarrattat     ";
        System.out.println("Original      = " + text);
        System.out.println("text.length() = " + text.length());

        // The trim() method will result a new string object with a leading and
        // trailing while space removed.
        text = text.trim();
        System.out.println("Result        = " + text);
        System.out.println("text.length() = " + text.length());
    }
}

The result of the code snippet above:

Original      =      tattarrattat     
text.length() = 22
Result        = tattarrattat
text.length() = 12

How do I add leading zeros to a number?

By I Wayan Saryada in Core API, Lang Package 1 Comment

This example shows you how to use the String.format() method to add zero padding to a number. If you just want to print out the result you can use System.out.format(). This method is available since Java 1.5, so If you use a previous version you can use the NumberFormat class, see: How do I format a number with leading zeros?.

package org.kodejava.lang;

public class LeadingZerosExample {
    public static void main(String[] args) {
        int number = 1500;

        // String format below will add leading zeros (the %0 syntax)
        // to the number above. The length of the formatted string will
        // be 7 characters.
        String formatted = String.format("%07d", number);

        System.out.println("Number with leading zeros: " + formatted);
    }
}

Here is the result of the code snippet above:

Number with leading zeros: 0001500

For more information about the format syntax you can find it here.

How do I calculate process elapsed time?

By I Wayan Saryada in Core API, Lang Package 0 Comment

This example shows us how to use the System.nanoTime() method to get the amount of time a process take place. Please be aware that the nano time value is not related to the real world time value.

package org.kodejava.lang;

public class ElapsedTimeExample {
    public static void main(String[] args) {
        // Get the start time of the process
        long start = System.nanoTime();
        System.out.println("Start: " + start);

        // Just do some a bit long process calculating the total value
        // of even number from zero to 10000
        int totalEven = 0;
        for (int i = 0; i < 10000; i++) {
            if (i % 2 == 0) {
                totalEven = totalEven + i;
            }
        }

        // Get the end time of the process
        long end = System.nanoTime();
        System.out.println("End  : " + end);

        long elapsedTime = end - start;

        // Show how long it took to finish the process
        System.out.println("The process took approximately: "
            + elapsedTime + " nano seconds");
    }
}

And example of the result are:

Start: 35034476484699
End  : 35034477434200
The process took approximately: 949501 nano seconds

How do I use for-each in Java?

By I Wayan Saryada in Core API, Lang Package 0 Comment

Using for-each command to iterate arrays or a list can simplified our code. Below is an example how to do it in Java. The first loop is for iterating array and the second for iterating a list containing a some names.

package org.kodejava.lang;

import java.util.ArrayList;
import java.util.List;

public class ForEachExample {
    public static void main(String[] args) {
        Integer[] numbers = {10, 100, 1000, 10000, 100000, 1000000};

        for (Integer i : numbers) {
            System.out.println("Number: " + i);
        }

        List<String> names = new ArrayList<>();
        names.add("Musk");
        names.add("Nakamoto");
        names.add("Einstein");

        for (String name : names) {
            System.out.println("Name: " + name);
        }
    }
}

The result of the code snippet:

Number: 10
Number: 100
Number: 1000
Number: 10000
Number: 100000
Number: 1000000
Name: Musk
Name: Nakamoto
Name: Einstein