Increase the size of an array

In Java there is no direct way to increase the size of an array after is is defined.
In this post I will show you how to do this easily.
Think you have following array. The size of this array is 1.

String[] arr = new String[1];

Now you can increase the size of your array like this.(replace the word "NEW_SIZE" with your new size)

arr=(String[]) Arrays.asList(arr).toArray(new String[NEW_SIZE]);

How to read a file line by line in Java

In this example I explain how to read a text file line by line and add the lines to a List.

 import java.io.BufferedReader;
 import java.io.FileReader;
 import java.io.IOException;
 import java.util.ArrayList;
 import java.util.List;
 import javax.swing.JOptionPane;


 public static void main(String[] args) throws IOException {
   String fileName = "c:\\camera.log"; \\This is the path to your
                                       file
   FileReader reader = new FileReader(fileName);
   BufferedReader buffReader = new BufferedReader(reader);
   List<string> linesList = new ArrayList<string>();
   String line;
   while((line = buffReader.readLine()) != null){
     linesList.add(line);
   }
   //For the purpose of this example I just show a message box to
    display the content of the file.
   JOptionPane.showMessageDialog(null, linesList.toArray());
}

How to center the form(JFrame) in the screen in java

This example shows how to center a form in your screen

 import java.awt.Dimension;

 import java.awt.Toolkit;

 import javax.swing.JFrame;

 public static void main(String[] args){

    JFrame myForm = new JFrame("Centered Form");
    myForm.setSize(250, 200);
    Toolkit toolkit = Toolkit.getDefaultToolkit();
    Dimension screenSize = toolkit.getScreenSize();
    //Following three lines make the form centered
    int x = (screenSize.width - myForm.getWidth())/2;
    int y = (screenSize.height - myForm.getHeight())/2;
    myForm.setLocation(x, y);
    myForm.setVisible(true);

}

How to open a file with associated program in Java

First you need following imports

  import java.awt.Desktop;
  import java.io.File;
  import java.io.IOException;

Now you can create a Desktop object and call the open() method.

  Desktop desktop = Desktop.getDesktop();
  File f = new File("C:\\readme.txt");
  try {
    desktop.open(f);
  } catch (IOException ex) {}

In java how to replace a character or a word at a given position.

Lets assume that you want to replace the 7th character ("-") in following string with "*" character.
Then you can do it as below.

 String s = "I*LIKE-JAVA BUT MY FRIEND LIKE .NET.";
 System.out.println(s.substring(0,6) + "*" + s.substring(6+1));

Note that in above string there are two occurrences of the word "LIKE".
If you want to replace the first occurances of the word "LIKE" with the word "LOVE" then you can do it as below.

 String s = "I*LIKE-JAVA BUT MY FRIEND LIKE .NET.";
 System.out.println(s.substring(0,2) + "LOVE"+ s.substring(2+4));

Below example shows you how to remove a character at a certain position.
In this example we remove the "*" characterfrom the text.

 String s = "WE*LIKE";
 System.out.println(s.substring(0,2) + s.substring(3));

If you want to remove all the "*" from the string "I*LOVE*JAVA" then you can use below method.

 String initialString = "I*LOVE*JAVA";
 String result = "";
 for (int i = 0; i < initialString.length(); i ++) {
   if (initialString.charAt(i) != '*') {
     result += initialString.charAt(i);
   }
 }
 System.out.println(result);

Split a string at asterisk(*) character

In this case you have to escape the asterisk(*) character as below.

String s = "I*LOVE*JAVA";
String[] parts = s.split("\\*");
for (int i = 0; i < parts.length; i++) {
  System.out.println(parts[i]);
}

How to copy a file from one folder to another folder in Java

Assume that you want to copy the file "C:\\a.txt" to another location. Then you can use following method. 
You can easily change the name of the second file at the same time.
(Note that my first file is a.txt and the name of the new file is b.txt)

try {
  String path1 = "C:\\a.txt";
  String path2 = "D:\\b.txt";
  File file1 = new File(path1);
  File file2 = new File(path2);
  FileInputStream fis = new FileInputStream(file1);
  FileOutputStream fos = new FileOutputStream(file2);
  byte[] byteArray = new byte[1024];
  int i = 0;
  while((i = fis.read(byteArray) )!= -1) {
    fos.write(byteArray, 0, i);
  }
  fis.close();
  fos.close();
} catch (Exception e) {
  e.printStackTrace();
}