This tutorial explains about what are the differences between Iterators and Enumeration and similarity of both interface which may be asked in a core java interview. Functionalities of both Iterator & Enumeration interfaces are similar that means both generates a series of all elements of the object which is to have its values iterated that can be traversed one at a time using next() method incase of Iterator and nextElement() method incase of Enumeration. The more powerful newer interface Iterator takes place of the old interface Enumeartion in the Java Collections Framew...

When we try to install wxPython lib on Ubuntu system to do software GUI development,most of time we may meet some installation and lib dependency problems. For the latest Ubuntu version, the problems still happen. Below are some common problems which happened frequently and their solution:---------------------------------------------------------------------------------------------------------------Problem [1]: Install wxPython on Ubuntu 20.04 fail because of dependency package Gtk is not installed.Error Message:No package 'gtk+-3.0' found Package gthread-2.0 was not found in the pkg-config sea...

According to Oracle documentation, ThreadLocal is a class provides thread-local variables. These variables differ from their normal counterparts in that each thread that accesses one (via its get or set method) has its own, independently initialized copy of the variable. ThreadLocal instances are typically private static fields in classes that wish to associate state with a thread. In short, ThreadLocal variables are variables belong to a thread, not a class or an instance of a class.One common use of ThreadLocal is when you want to access some non thread-safe objects in threads without using ...

A certificate is often used to prove the identity of a server. The certificate will contain information such as the subject and issuer of the certificate. It will also contain the validation date of the certificate. A certificate is often exported to an external cert file which is transferred over the internet. We will often see its use in SSL communication which provides secure communication between two entities.In this post, we will show how to read the data from an external certificate file and generate a X509 certificate object with the data. This object can then be used to conduct other o...

In C++/CLR (for Microsoft), sometimes we need to convert int to System::String type or vice versa. The simple way is :From System::String^ to int int num= int::Parse(str); // System::String^ to intFrom int to System::String^System::String^ str = num.ToString(); // int to System::String^For all the other data types, similar ways can be adopted....

When we write programs, we may often get into a situation where we don't know whether we should use Abstract class or Interface when we want to define an abstract object. These two are very similar and they are interchangeable in many cases. On Stackoverflow, this question is asked lots of times and it's related to many programming languages. Also in the official documentation of PHP regarding the Abstract class and Interface, people are arguing about this. To understand this question, their differences and use scenarios need to be understood first.Abstract class and Interface structureFor Abs...

Sometimes when handling a long running process, there would be need to track the progress so that people know something is still running instead of doubting something goes wrong. In this case, a progress bar which indicates the current status and progress would be desired.This post will show an example on how to implement progress bar using GoLang. Let's take a look at the final outcome first before jumping into the implementation detail.The key in the implementation is actually just the \r control flag for fmt.Printf(). \r is actually the carriage return control which tells the cursor to move...

In GoLang, we can format and produce string using fmt.Printf(), just like C, GoLang also supports format verbs like %s, %d which can be placeholder for different types of values. But please pay attention when printing error as string so that you will not fall into some trap.Let's first take an example code snippet and see what trap we are talking about.package mainimport "fmt"type A stringfunc (a A) Error() string { return fmt.Sprintf("%s is an error", a)}func main() { a := A("hello") fmt.Printf("error is %s", a)}What do you expect the output is? Do you expect "error is hello is an error"? Unf...