How do I insert a string to a StringBuffer?

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

public class StringBufferInsert {
    public static void main(String[] args) {
        StringBuffer buffer = new StringBuffer("kodeava");
        System.out.println("Text before        = " + buffer);

        //  |k|o|d|e|a|v|a|....
        //  0|1|2|3|4|5|6|7|...
        //
        // From the above sequence you can see that the index of the
        // string is started from 0, so when we insert a string in
        // the fourth offset it means it will be inserted after the
        // "e" letter. There are other overload version of this
        // method that can be used to insert other type of data such
        // as char, int, long, float, double, Object, etc.
        buffer.insert(4, "j");
        System.out.println("After first insert = " + buffer);

        // Here we insert a string to the StringBuffer at index 8
        buffer.insert(8, " examples");
        System.out.println("Final result       = " + buffer);
    }
}

The program will print the following output:

Text before        = kodeava
After first insert = kodejava
Final result       = kodejava examples

How do I remove some characters from a StringBuffer?

By Wayan in Core API, Lang Package 0 Comment

The example below show you to remove some elements of the StringBuffer. We can use the delete(int start, int end) method call to remove some characters from the specified start index to end end index. We can also remove a character at the specified index using the deleteCharAt(int index) method call.

package org.kodejava.lang;

public class StringBufferDelete {
    public static void main(String[] args) {
        String text = "Learn Java by Examples";

        // Creates a new instance of StringBuffer and initialize
        // it with some text.
        StringBuffer buffer = new StringBuffer(text);
        System.out.println("Original text  = " + buffer);

        // We'll remove a sub string from this StringBuffer starting
        // from the first character to the 10th character.
        buffer.delete(0, 10);
        System.out.println("After deletion = " + buffer);

        // Removes a char at a specified index from the StringBuffer.
        // In the example below we remove the last character.
        buffer.deleteCharAt(buffer.length() - 1);
        System.out.println("Final result   = " + buffer);
    }
}

Output of the program is:

Original text  = Learn Java by Examples
After deletion =  by Examples
Final result   =  by Example

How do I get char value of a string at a specified position?

By Wayan in Core API, Lang Package 0 Comment

The chartAt() method of the String class returns the char value at the specified index. An index ranges from 0 to length() - 1. If we specified an index beyond of this range a StringIndexOutOfBoundsException exception will be thrown.

These method use zero based index which means the first char value of the sequence is at index 0, the next at index 1, and so on, as for array indexing.

package org.kodejava.lang;

public class CharAtExample {
    public static void main(String[] args) {
        String[] colors = {"black", "white", "brown", "green", "yellow", "blue"};

        for (String color : colors) {
            // Get char value of a string at index number 3. We'll get the 
            // fourth character of each color in the array because the 
            // index is zero based.
            char value = color.charAt(3);
            System.out.printf("The fourth char of %s is '%s'.%n", color, value);
        }

    }
}

Here is the program output:

The fourth char of black is 'c'
The fourth char of white is 't'
The fourth char of brown is 'w'
The fourth char of green is 'e'
The fourth char of yellow is 'l'
The fourth char of blue is 'e'

How do I create a console progress bar?

By Wayan in Core API, Lang Package 1 Comment

The code below demonstrates how to create a progress bar in a console program. The trick is to print the progress status using a System.out.print() and add a carriage return character ("\r") at the end of the string to return the cursor position to the beginning of the line and print the next progress status.

package org.kodejava.lang;

public class ConsoleProgressBar {
    public static void main(String[] args) {
        char[] animationChars = new char[]{'|', '/', '-', '\\'};

        for (int i = 0; i <= 100; i++) {
            System.out.print("Processing: " + i + "% " + animationChars[i % 4] + "\r");

            try {
                Thread.sleep(200);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }

        System.out.println("Processing: Done!");
    }
}

How do I calculate process execution time in higher resolution?

By Wayan in Core API, Lang Package 0 Comment

This example demonstrates how to use the System.nanoTime() method to calculate processing execution time in higher resolution. The processing time calculated in nanoseconds resolution.

package org.kodejava.lang;

public class NanoSecondsTimerResolution {
    public static void main(String[] args) {
        // Get process execution start time in nanoseconds.
        long start = System.nanoTime();
        System.out.println("Process start... " + start);

        try {
            Thread.sleep(5000); // Simulate a long process.
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

        // Get process execution finish time in nanoseconds.
        long finish = System.nanoTime();
        System.out.println("Process finish... " + finish);

        // Calculate the process execution time.
        long execTime = finish - start;
        System.out.println("Processing time = " + execTime + "(ns)");
    }
}