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  Signature sign/verification demo in Java

Digital signature is commonly used in areas where data authentication and integrity are required. It is extremely important to have signature while transferring sensitive data from one peer to other peers through network since there might be malicious applications or man-in-the-middle attacks which may alter the data along the way. Java provides some APIs to generate and verify digital signature. One important class is Signature.  When generating the signature, a private key needs to be pa...

   SECURITY,JAVA,SIGNATURE     2015-11-21 09:48:12

  Recover deleted file in Linux EXT3 file system

Environment : CentOS 5.3 x86_64, /dev/sdb1 is the data segment /data0. EXT3 file system. Problem : /data0/tcsql/cankao/phpcws-1.5.0/httpcws.cpp is deleted mistakenly and httpcws.cpp is not backed up. It will take much time to rewrite this program again. So we must recover it back. debugfs is feasible in EXT2 file system, but in EXT3 file system, it's not very useful. There is one open source software called ext3grep which can help us recover deleted file in EXT3 file system. The recovery steps a...

   Linux,EXT3,File recovery     2013-08-16 07:06:45

  New Features to Look Out for in Xcode 9

When we say Xcode, we mean a designing toolset which is completely packed with features. Using this Xcode, developers can create applications for platforms such as the Apple TV, the iPad, Apple Watch, and the iPhones and even for the Macintosh. The development system for Xcode has a mixture of features. These are called the instrument analysis tool, simulators, and the ever important OS frameworks which are present in the package in a variety of form of tvOS SDKs, iOS SDKs, watchOS SDKs, and the...

   XCODE,IPHONE,XCODE9     2017-09-26 06:31:30

  Why can System.out.println be used to exit while loop

Let's first take a look at one simple Java thread code snippet which is supposed to exit the while loop after the first loop run. public class StopThread { private static boolean stopRequested; public static void main(String[] args) throws InterruptedException { Thread backgroundThread = new Thread(new Runnable() { @Override public void run() { int i = 0; while (!stopRequested) { i++; } } }); backgroundThread.start(); TimeUnit.SECONDS.sleep(1); stopRequested = true; } } But the tr...

   JAVA,THREAD,VOLATILE     2018-12-21 19:25:54

  Access control in Java -- doPrivileged

Previously we have introduced how Java performs permission check to protect resource access. What if sometimes we need to give some class the temporary access to some resource which it initially doesn't have? AccessController provides six doPrivileged methods to fulfill this requirement. These six methods have below signatures : static T doPrivileged(PrivilegedAction action)static T doPrivileged(PrivilegedAction action, AccessControlContext context)static T doPrivileged(PrivilegedExceptionA...

   JAVA,SECURITY,DOPRIVILEGED     2016-03-08 05:46:42

  Different ways to print "Hello world" in Java

This post is not about best practice to print "Hello world" in Java, it is about exploring different capabilities offered by Java. Also there are articles about printing "Hello world" in different programming languages, but this post is not about that. Standard literal The most commonly used way is to use System.out to print"Hello world". System.out.println("Hello world"); Enumeration An enumeration can define a set of values belonging to one category. For example, an enumeration for all months ...

   JAVA,FEATURE     2016-05-21 21:49:48

  Remote execute command in Java example

Frequently there is a need to logon to a remote system and run some commands or programs to get the output, many software can serve this purpose such as putty and gitshell.These software usually provide secure access to the remote system. But have you ever wondered what to do if you need to run commands on many different systems at the same time and get all these results back at a single place? Especially in big data era, many tasks may run on different distributed systems and you want o have a ...

   JSch, Example, Distributed system, SSH2     2014-12-12 03:20:19

  Make a directory using C++ for windows

If you want to create a folder at windows using c++/cpp language, there is an easy way for make a folder. You can do it just including the <windows.h> header file. To make a folder at C:\ drive named "deadman"#include<windows.h>int main(){   CreateDirectory ("C:\\deadman", NULL);   return 0;}If you want to delete a fodler from the C:\ directory.#include<windows.h>int main(){   RemoveDirectory("C:\\deadman");   retur...

   C++,Directory,Windows,CreateDirectory,Example     2012-02-25 04:26:16

  Beginners guide to Linux directory structure

Have you ever looked in your / directory, you’ll see a lot of directories. Here we are presenting beginners guide to linux directory structure explaining what they mean and what are the contents of these directories.Screenshot of contents of root directory: /This is called root partition. All files and directories start with root partition. Write privileges under this directory are avaible with root user only. Not to confuse it with root user’s home directory, know the ...

   Linux,File system structure,Beginner's guide     2012-04-20 12:19:32

  Can private method be overridden?

The private methods are not inherited by subclasses and you cannot be overridden by subclasses. According to Java Language Specification (8.4.8.3 Requirements in Overriding and Hiding), "Note that a private method cannot be hidden or overridden in the technical sense of those terms. This means that a subclass can declare a method with the same signature as a private method in one of its superclasses, and there is no requirement that the return type or throws&nb...

   Java,Private method,overridding,impossib     2011-10-06 03:57:14

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