How do I calculate process elapsed time?

By Wayan 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 Wayan 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

How do I convert string to an integer or number?

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

public class StringToInteger {
    public static void main(String[] args) {
        // Some random selected number, could representing a decimal,
        // hexadecimal or octal number.
        String myLuckyNumber = "13";

        // We convert a string to an integer by invoking parseInt() method
        // of the Integer class.
        int number = Integer.parseInt(myLuckyNumber);
        System.out.println("My lucky number is: " + number);

        // We can also converting a string representation of a number other
        // then the decimal base, for instance an hexadecimal by providing
        // the radix to the method.
        number = Integer.parseInt(myLuckyNumber, 16);
        System.out.println("My lucky number is: " + number);

        number = Integer.parseInt(myLuckyNumber, 8);
        System.out.println("My lucky number is: " + number);
    }
}

Our code results are:

My lucky number is: 13
My lucky number is: 19
My lucky number is: 11

How do I know the memory size in virtual machine?

By Wayan in Core API, Lang Package 0 Comment

If you want to know the free memory, and the total memory available in the Java runtime environment then you can use the following code snippet to check.

package org.kodejava.lang;

public class MemoryExample {
    public static void main(String[] args) {
        long freeMemory = Runtime.getRuntime().freeMemory();
        long totalMemory = Runtime.getRuntime().totalMemory();

        System.out.println("Free Memory  = " + freeMemory);
        System.out.println("Total Memory = " + totalMemory);
    }
}

Here is the result of the code snippet above:

Free Memory  = 1018439896
Total Memory = 1029177344

How do I reverse a string?

By Wayan in Core API, Lang Package 1 Comment

Below is an example code that reverse a string. In this example we use StringBuffer.reverse() method to reverse a string. In Java 1.5, a new class called StringBuilder also has a reverse() method that do just the same, one of the difference is StringBuffer class is synchronized while StringBuilder class is not.

And here is the string reverse in the StringBuffer way.

package org.kodejava.lang;

public class StringReverseExample {
    public static void main(String[] args) {
        // The normal sentence that is going to be reversed.
        String words =
                "Morning of The World - The Last Paradise on Earth";

        // To reverse the string we can use the reverse() method in
        // the StringBuffer class. The reverse() method returns a
        // StringBuffer so we need to call the toString() method to
        // get a string object.
        String reverse = new StringBuffer(words).reverse().toString();

        // Print the normal string
        System.out.println("Normal : " + words);
        // Print the string in reversed order
        System.out.println("Reverse: " + reverse);
    }
}

Beside using this simple method you can try to reverse a string by converting it to character array and then reverse the array order.

And below is the result of the code snippet above.

Normal : Morning of The World - The Last Paradise on Earth
Reverse: htraE no esidaraP tsaL ehT - dlroW ehT fo gninroM