Today's Question:  What does your personal desk look like?        GIVE A SHOUT

SEARCH KEYWORD -- key-value

  Why accessing Java HashMap may cause infinite loop in concurrent environment

HashMap in Java is frequently used to handle key/value pairs. But it is not a good candidate to be used in concurrent environment where ConcurrentHashMap should be used instead. If used in concurrent environment, it may cause lots of unexpected behavior even including make the program getting into an infinite loop situation. To understand how this can happen, let's first discuss how HaspMap works internally. In this post we will use implementation of HashMap before Java 8 as example, Java 8 prov...

   JAVA,HASHMAP,INFINITE LOOP     2020-03-29 01:47:00

  Different types of keystore in Java -- Windows-MY

Windows-MY is a type of keystore on Windows which is managed by the Windows operating system. It stores the user keys and certificates which can be used to perform cryptographic operations such as signature verification, data encryption etc. Since it's a kind of native keystore, Java doesn't have a general API to access it. To help Java applications access the keys and certificates stored in Windows-MY keystore, Java provides a separate API -- SunMSCAPI. The SunMSCAPI provider is ...

   JAVA,KEYSTORE,WINDOWS-MY,SUNMSCAPI     2016-01-09 05:45:59

  JSON unmarshal in GoLang

In almost all mainstream programming languages, there is either built-in or third-party library to support parse JSON data because it is so popular for organizing and transferring data among different services. In GoLang, the built in json package also provides functions for marshalling and unmarshalling JSON data. Marshalling GoLang struct to a JSON string is relatively simple, just need to call json.Marshal(), it's a bit complicated to unmarshal an arbitrary JSON string into a GoLang struct ob...

   GOLANG,JSON,UNMARSHAL,EMPTY INTERFACE     2019-11-09 21:57:30

  How to Convert Images on Mac Finder

If you have a lot of images in different formats and you want to convert them to a common format, you can use the Mac Finder to do it easily and quickly. Here are the steps to follow: 1. Open the Finder and navigate to the folder where your images are stored. 2. Select the images that you want to convert. You can use the Shift key or the Command key to select multiple images at once. 3. Right-click on the selected images and choose Services > Preview from the context menu. This will open the ...

   MACOS,FINDER,IMAGE CONVERSION     2023-04-16 02:09:54

  Why exception would be thrown when deleting element while looping through HashMap in Java

HashMap and other Collection types are frequently used in Java application programming. This post will explain why exception would be thrown when deleting element with Map.remove() while looping through a Map using Iterator. This issue would also occur to other Collection types such as Set, List. Below is a sample code snippet demonstrating the exception thrown. Map<String,String> map = Collections.synchronizedMap(new TreeMap<String,String>()); map.put("key1","value1"); map.put("ke...

   JAVA,HASHMAP,CONCURRENTMODIFICATIONEXCEPTION     2018-06-30 12:49:09

  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

  Generate certificate in Java -- Self signed certificate

This is the first post in this series which I will show you how to generate SSL certificate in Java programmatically. Certificates are frequently used in SSL communication which requires the authentication of server to client. This is to make the client to trust that the server is actually the one it claims. Certificates are really important on the Internet. All HTTPS communications on the Internet need the server side to present their certificates signed by trusted CAs. The basic flow of a requ...

   Java,Certificate,X509     2014-07-30 07:42:18

  A Programming Idiom You've Never Heard Of

Here are some sequences of events: Take the rake out of the shed, use it to pile up the leaves in the backyard, then put the rake back in the shed. Fly to Seattle, see the sights, then fly home. Put the key in the door, open it, then take the key out of the door. Wake-up your phone, check the time, then put it back to sleep. See the pattern? You do something, then do something else, then you undo the first thing. Or more accurately, the last step is the inverse of the first. Once you're aware ...

   Programming,Idiom,Strange     2012-01-04 08:12:25

  How does JGSS read Windows native TGT credential?

MS LSA is a protected subsystem that authenticates and logs users onto the local system. The user credential is stored at the native credential cache of LSA on Windows. This kind of credential is often used to authenticate the user to the server, one of the authentication methods is Kerberos. JGSS has provided a native interface which can read the native TGT credential and use it to get the TGS of a service. But how does JGSS read the native TGT credential? Here is a sample code for reading nati...

   KERBEROS,JGSS,MS LSA,NATIVE CREDENTIAL,TGT,SESSION KEY TYPE     2015-03-25 03:42:32

  What is encryption? Its role in the modern age

“Messages and calls are end-to-end encrypted.” If you are a WhatsApp user, you must have read this statement at the top of chats you open. Now, what does it mean? The statement signifies that all the messages or voice notes shared between users are encrypted, and no one can read or listen in on them. As mostly all of us use messaging apps and emails, information security has become a major concern. Moreover, we don’t know how many digital footprints we leave on the web can be t...

   DATA SECURITY,VPN     2021-01-21 08:04:16

RECENT