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  How to Understand and Use nil in Golang Correctly?

In Golang, nil is a predefined identifier that carries different meanings in various contexts, but typically represents "none", "empty" or "zero value". It can be assigned to variables of pointer, slice, map, channel, function, and interface types. Understanding the significance of nil is crucial for writing robust Go programs, as mishandling nil can lead to unexpected issues. nil in Pointers In Go, pointers are a fundamental type that stores the memory address of a variable. When a pointer is d...

   FUNCTION,SLICE,MAP,CHANNEL,GOLANG,NIL     2024-01-05 05:19:40

  Time to think about supporting max/min functions for integers in GoLang

Sometime back we wrote a post explaining why there is no max/min function support for integers in GoLang, one of the reasons is that no overloading is supported and the function name has been used for other numeric types float64. To solve this problem and make max/min function support integer as well, either GoLang should support overloading like in Java or the same set of functions need to be created in a different package other than standard math. These don't look like good options as overload...

   MIN,MAX,GENERICS,GOLANG     2021-07-24 03:14:42

  Greedy and Nongreedy Matching in a Regular Expression

By default, pattern matching is greedy, which means that the matcher returns the longest match possible. For example, applying the pattern A.*c to AbcAbcA matches AbcAbc rather than the shorter Abc. To do nongreedy matching, a question mark must be added to the quantifier. For example, the pattern A.*?c will find the shortest match possible. COPY // Greedy quantifiers String match = find("A.*c", "AbcAbc"); // AbcAbc match = find("A.+", "AbcAbc"); // AbcAbc // Nongreedy quantifier...

   Regular expression,Pattern match,Greedy,     2011-08-09 12:42:28

  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

  Generate signed certificate from CSR in Java

In our previous tutorial, we have explained how to generate CSR which can be sent to CA for generating a signed certificate. In this tutorial, we will explain how to generate the signed certificate from CSR in Java. We will not use an actual CA but a self-signed certificate to act as a CA certificate. Since the CSR contains the subject information where a certificate needs to be generated and signed for. The key here is to extract the subject information from the CSR and then set it as the subje...

   JAVA,CSR,SIGN CERTIFICATE     2020-10-24 07:03:17

  A Hello, World Servlet

Servlets are the pure Java solution to handle web requests. Many application will use servlets instead of JSP and others will use servlets in conjunction with JSP. Experienced JSP programmers use servlets in conjunction with JSP to create clearer and simpler applications. The servlets handle Java processing: form handing, calculation and database queries. JSP formats the results. Servlets belong in WEB-INF/classes. On this machine, the source is in Java source in /var/www/hosts/www.caucho.com/we...

   Web.xml,Tomcat,Servlet,WEB-INF     2011-05-08 10:31:39

  Generate certificate in Java -- Store certificate in KeyStore

In previous post, we have explained how to create a certificate chain in Java. After generating the chain, we need to store it somewhere so that it can be used later when we are doing the actual SSL communication, either in a key store or trust store. This post will show you how to store the private key and its associated certificate chain in a keystore file. There are different types of keystore in Java, in this post, we will choose the JKS to demonstrate how to store the certificate chain. Whe...

   Java,Certificate chain,Keystore     2014-08-20 03:56:39

  Will nil == nil be true in GoLang

There is some interview question may ask whether nil == nil be true in GoLang. Wil it be true. false or compilation error? To know the answer, some knowledge about nil in GoLang needs to be explained first. nil definition According to Go's official documentation, the definition of nil is // nil is a predeclared identifier representing the zero value for a // pointer, channel, func, interface, map, or slice type. var nil Type // Type must be a pointer, channel, func, interface, map, or slice type...

   GOLANG,NIL,NIL EXPLANATION     2021-08-08 02:54:15

  Finding selected checkbox items in a JSF dataTable

This is one of those problems that I couldn’t find a complete example for when I needed it, so hopefully this will save somebody else the extra time it took me to piece it together. We frequently need to have data tables in our UI, and allow the user to select a subset of those items for action. In JavaServer Faces, this means having a DataTable, each row having its own checkbox. But when the action is triggered, how to we find which items the user has selected. The first step is to ...

   JavaServer Faces,JSF,Datatable,Checkbox,Example     2012-01-03 03:02:46

  Android create button tutorial

This tutorial assumes that you already have an activity and are using an XML layout. Open the layout XML and add the button element.  Assign an ID with the “@+id” operator.  The + tells Android to generate an ID for this element so that you can reference it in your Java files. This is an example. Your layout and text elements will probably be very different. In this example case, the ID of the button is “close”. <Button android:id="@+id/close" android:lay...

   Android,Simulator,Button,XML,Tutorial     2014-11-07 08:30:10

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