How to create SFTP connection using java ?

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In this blog post we will learn how to create a secure FTP connection using java.SFTP is much more secure than its predecessor FTP since SFTP is based on SSH.
Here We will develop a SFTP client.Basically SFTP clients are programs that use SSH to access, manage, and transfer files. SFTP clients are functionally similar to FTP clients, but they use different protocols.
To create a SFTP connection to a server for file transfer or any other FTP operation we will use an open source library called JSCh. You can download this library from http://www.jcraft.com/
Add this library to your class path and start creating the program.
This example shows how to get a file from the server using SFTP.

package com.techy.rajeev;

import com.jcraft.jsch.*;

    /**
     * @param args
     */

    public class SFTPTest {
    public static void main(String args[]) {
        JSch jsch = new JSch();
        Session session = null;
        String username="";//Put your username here
        String password="";//Put your password here
        String host="";//Hostname
        String sourceFile="";//Path of file on the server
        String destFile="";//Path of local file
        try {
            session = jsch.getSession(username,host,22);
            session.setConfig("StrictHostKeyChecking", "no");
            session.setPassword(password);
            session.connect();

            Channel channel = session.openChannel("sftp");
            channel.connect();
            ChannelSftp sftpChannel = (ChannelSftp) channel;

            sftpChannel.get(sourceFile,destFile);
            sftpChannel.exit();
            session.disconnect();
        } catch (JSchException e) {
            e.printStackTrace(); 
        } catch (SftpException e) {
            e.printStackTrace();
        }
    }

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Java program to generate all possible sub string of a string

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This simple java program generates all possible sub string of given string.You can replace string with StringBuilder or StringBuffer where performance is issue.

package com.techy.rajeev;

public class GenStr {

    /**
     * @param args
     */
    public static void genAllSubStr(String str){
        for(int i=0;i<str.length();i++){
            for(int j=i;j<str.length();j++){
                System.out.println(str.substring(i, j+1));
            }
        }
    }
    public static void main(String[] args) {
        genAllSubStr("abc");
    }

}

Output:

a
ab
abc
b
bc
c

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Java program to generate permutation of a string

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This post is about generating permutation of a string using a java program.This program has a static method  genPerm() method which is used for generation of permutation of the string. genPerm() method is recursive and takes two string arguments and prints the permutations of the second string.
Source Code:

public class GeneratePerm {

    /**
     * @param args
     */
    public static void genPerm(String pString,String sb){
        if(pString.length()==3)
            System.out.println(pString);
        for(int i=0;i<sb.length();i++){
            genPerm(pString+sb.charAt(i),sb.replaceFirst(sb.charAt(i)+"",""));
        }
    }
    public static void main(String[] args) {
        String sb=new String("abc");
        genPerm("",sb);
    }

}

Output:

abc
acb
bac
bca
cab
cba

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