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Java – Default Capacity of Vector

admin — Mon, 31 May 2010 04:18:18 +0000

Find default capacity of Vector in JAVA

In this example, We will find default capacity of vector in collections in java.

import java.util.Vector;
public class VectorSize {

	public static void main(String[] args) {

		Vector vc=new Vector();

		System.out.println("Default Capacity of Vector is :"+vc.capacity());

		vc.add("first element");

		System.out.println("Default Capacity of Vector after one element :"+vc.capacity());

		vc.add("second element");

		System.out.println("Default Capacity of Vector after two elements :"+vc.capacity());
	}
}

Output

Default Capacity of Vector is :10
Default Capacity of Vector after one element :10
Default Capacity of Vector after two elements :10

Java – Remove Duplicate Object in Collection

admin — Wed, 07 Apr 2010 03:21:42 +0000

Removing Duplicate Object from Array through collection framework

In this example, We will find and search duplicate elements in array and remove that object from collections in java.

Duplicate object in array will explain how to remove in java J2EE program and application.

import java.util.*;

public class RemoveDuplicate {

    public static void main(String[] args) {
          ArrayList<String> arrayList1 = new ArrayList<String>();

          arrayList1.add("A");
          arrayList1.add("A");
          arrayList1.add("B");
          arrayList1.add("B");
          arrayList1.add("B");
          arrayList1.add("C");

          for (int i=0; i< arrayList1.size(); i++)
          {
            System.out.println("Having Duplicate Objects :"+arrayList1.get(i));
          } 

          Set<String> s=new TreeSet<String>();
          s.addAll(arrayList1);

          Iterator it=s.iterator();
          while (it.hasNext())
          {
            System.out.println("No Duplicate :"+(String)it.next());
          } 

    }
}

Output

Having Duplicate Objects :A
Having Duplicate Objects :A
Having Duplicate Objects :B
Having Duplicate Objects :B
Having Duplicate Objects :B
Having Duplicate Objects :C
No Duplicate :A
No Duplicate :B
No Duplicate :C

Multithreading in Java

admin — Mon, 05 Apr 2010 16:56:18 +0000

Multithreading in Java

In this multithreading programming example, We will use Runnable interface to implements in main class to run multithreading in java.

Multi threading programming will explain how to use Runnable Interface in java J2EE program and application.

1. MainThreadClass.java

public class MainThreadClass {

    public static void main(String[] args) {

        ThreadClass tc1=new ThreadClass("Run");
        ThreadClass tc2=new ThreadClass("Thread");

        Thread t1=new Thread(tc1);
        Thread t2=new Thread(tc2);

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

2. ThreadClass.java

public class ThreadClass implements Runnable{

    String msg;

    public void run()
    {
        for(int i=0;i<=5;i++)
        {
            System.out.println("Run method: "+msg);
        }
    }

    ThreadClass(String mg)
    {
        msg=mg;
    }
}

Output

Run method: Run
Run method: Run
Run method: Run
Run method: Thread
Run method: Thread
Run method: Thread
Run method: Run
Run method: Run
Run method: Thread
Run method: Thread
Run method: Run
Run method: Thread

Java – Multithreading Example with Thread Class

admin — Sun, 04 Apr 2010 16:32:59 +0000

Java MultiThreading Example

In this multithreading example, We will use Thread class to extends in main class to run multithreading in java.

Multi threading will explain how to use Thread class in java J2EE program and code.

1. MainThreadClass.java

public class MainThreadClass {

    public static void main(String[] args) {

        ThreadClass dt1=new ThreadClass("Run");
        ThreadClass dt2=new ThreadClass("Thread");

        dt1.start(); // this will start thread of object 1
        dt2.start(); // this will start thread of object 2
    }
}

2. ThreadClass.java

public class ThreadClass extends Thread{

    String msg;

    public void run()
    {
        for(int i=0;i<=5;i++)
        {
            System.out.println("Run method: "+msg);
        }
    }

    ThreadClass(String mg)
    {
        msg=mg;
    }
}

Output

Run method: Run
Run method: Run
Run method: Run
Run method: Thread
Run method: Run
Run method: Run
Run method: Thread
Run method: Thread
Run method: Thread
Run method: Thread
Run method: Run
Run method: Thread

Multithreading can be used in print commands

Java – Interface Example

admin — Mon, 21 Dec 2009 14:53:57 +0000

Java interface example

This example will explain how to implement interface in java

Interface

JavaInterface.java

/**
 * This is interface which can implement in java class
 */
public interface JavaInterface {

    public void add();

    public void delete();

    public void find();

    public void edit();

}

class which implementing interface

JavaClassInterfaceExample.java

public class JavaClassInterfaceExample implements JavaInterface{

    public void add()
    {
        // statements
        System.out.println("add method implement by interface");
    }

    public void edit()
    {
        // statements
    }

    public void find()
    {
        // statements
    }

    public void delete()
    {
        // statements
    }

    public static void main(String args[])
    {
        JavaClassInterfaceExample jie = new JavaClassInterfaceExample();
        jie.add();
    }
}

Output

add method implement by interface

Java – Read file without DataInputStream

admin — Sun, 20 Dec 2009 13:45:21 +0000

Read File in java without DataInputStream class. DataInputStream class is deprecated. Instead of DataInputStream class we can use BufferedReader to read file in java.

This example will explain read file in java.

import java.io.File;
import java.io.FileInputStream;
import java.io.BufferedReader;
import java.io.InputStreamReader;

public class JavaReadFileExample {

    public static void main(String[] args) {

        File f=new File("c:\\readFileinJava.txt");

        try {
            FileInputStream fs = new FileInputStream(f);
            InputStreamReader in = new InputStreamReader(fs);
            BufferedReader br = new BufferedReader(in);

            String text;

            while(true)
            {
                text=br.readLine();
                if(text==null)
                    break;
                System.out.println(text);
            }
        }
        catch (Exception e) {
            e.printStackTrace();
        }
    }
}

Java – Run shell command in java

admin — Sun, 20 Dec 2009 13:33:13 +0000

Execute Shell command can be run by Runtime class. Shell can be executed in linux or unix platform.

This example will explain how to run shell commands in java and execute commands in java.

public class JavaRunCommandExample {

    public static void main(String[] args) {

        Runtime r = Runtime.getRuntime();
        Process p = null;
        String cmd[] = {"/bin/sh","ls","-l"};

        try {
            p = r.exec(cmd);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

Java – Run ssh commands in linux

admin — Sun, 20 Dec 2009 10:50:46 +0000

To execute ssh command in Linux, we need to use java API to run command at Unix machine. java ssh API is required to run linux commands through ssh with user Authentication.

This example will explain how to execute ssh in java.

Download ganymed ssh jar and set classpath before running program

import java.io.*;
import ch.ethz.ssh2.*;
public class JavaRunSshCommandExample {

    public static void main(String[] args) {

        String hostname = "127.0.0.1";
        String username = "root";
        String password = "password";

        boolean isAuthenticated = false;

        try
        {
            Connection conn = new Connection(hostname);

            conn.connect();

            isAuthenticated=conn.authenticateWithPassword(username, password);

            if (isAuthenticated == false)
                throw new IOException("Authentication failed.");

            Session sess = conn.openSession();

            sess.execCommand("cd /;ls -l> out.txt");

            InputStream stdout = new StreamGobbler(sess.getStdout());
            InputStream stderr = new StreamGobbler(sess.getStderr());

            InputStreamReader insrout=new InputStreamReader(stdout);
            InputStreamReader insrerr=new InputStreamReader(stderr);

            BufferedReader stdoutReader = new BufferedReader(insrout);

            BufferedReader stderrReader = new BufferedReader(insrerr);

            while (true)
            {
                String line = stdoutReader.readLine();
                if (line == null)
                {
                    break;
                }
                System.out.println(line);
            }

            while (true)
            {
                String line = stderrReader.readLine();
                if (line == null)
                {    break;}
                System.out.println(line);
            }

            sess.close();

            conn.close();
        }
        catch (IOException e)
        {
            e.printStackTrace(System.err);
            System.exit(2);
        }
    }
}

Other java ssh api

Download j2ssh api

Java – Edit File Example, Modify File java

admin — Sun, 20 Dec 2009 10:02:19 +0000

File can be appended by File class and other input output stream. To write content in a file in java we need to use java.io package. File class is used to create a file at specific path. We can use either StringBuffer for text and content to store in file. In java we can write file with FileWriter class with BufferedWriter class. write() method is used to create file and write the content in file.

To edit file in java we need to search text which replace with new text. indexOf() method will search text in java and append() method will modify old content in string.

This example will explain how to edit file in java and modify text in file by java.

text file in c drive

Content in this text, abc change xyz with new content by java io package

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileWriter;
import java.io.IOException;
import java.io.InputStreamReader;

public class JavaIOEditFileExample {

    public static void main(String[] args) {

        File f=new File("c:\\appendOldFile.txt");

        FileInputStream fs = null;
        InputStreamReader in = null;
        BufferedReader br = null;

        StringBuffer sb = new StringBuffer();

        String textinLine;

        try {
             fs = new FileInputStream(f);
             in = new InputStreamReader(fs);
             br = new BufferedReader(in);

            while(true)
            {
                textinLine=br.readLine();
                if(textinLine==null)
                    break;
                sb.append(textinLine);
            }
              String textToEdit1 = "abc";
              int cnt1 = sb.indexOf(textToEdit1);
              sb.replace(cnt1,cnt1+textToEdit1.length(),"New Append text");

              String textToEdit2 = "xyz";
              int cnt2 = sb.indexOf(textToEdit2);
              sb.replace(cnt2,cnt2+textToEdit2.length(),"Second new edit text");

              fs.close();
              in.close();
              br.close();

            } catch (FileNotFoundException e) {
              e.printStackTrace();
            } catch (IOException e) {
              e.printStackTrace();
            }

            try{
                FileWriter fstream = new FileWriter(f);
                BufferedWriter outobj = new BufferedWriter(fstream);
                outobj.write(sb.toString());
                outobj.close();

            }catch (Exception e){
              System.err.println("Error: " + e.getMessage());
            }
    }
}

Output

Content in this text, New Append text change Second new edit text with new content by java io package

Java – How to execute command in java

admin — Wed, 16 Dec 2009 15:45:03 +0000

Runtime class is part of java.lang package. Runtime class helps us to execute command in operating system with process class. exec() method execute command in java with command in array string. This example will execute to open notepad in window.

Java runtime class example explains How to execute a command java.

public class JavaRunTimeCommandExecuteExample {

    public static void main(String[] args) {

        Runtime r = Runtime.getRuntime();
        Process p = null;
        String cmd[] = {"notepad.exe"};
        try {
            p = r.exec(cmd);
        } catch (Exception e) {
            System.out.println("error executing " + cmd[0]);
        }
    }
}