How to convert byte sizes into human readable format using Java. Convert from Kilobyte to Yottabyte.

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WSDL is an XML format for describing network services as a set of endpoints operating on messages containing either document-oriented or procedure-oriented information. WSDL stands for Web Services Description Language. The WSDL is an abstract definitions of ports and messages, being separated from the concrete implementation. Using this model to define the service allows the reuse of these definitions and also will allow to implement server and client independently.

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In a application you can have resources that are limited or time consuming to create a new one. e.g. a connection to a database, a new thread. A solution is to create a the limited resource once and reuse it. To address this problem the object pool pattern was introduced. The object pool design will have the mechanism to create a new object to keep the objects and to destroy the objects if necessary.

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A design pattern is a general solution to a common problem. The singleton pattern is used to restricts the instantiation of a class to one single object.

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By default, ssh listens for incoming connections on port 22. So if a hacker wants to attack your machine he will most likely scan port 22 first. Just to make an idea how important is this (from my point of view of course), before changing the default ssh port for my server I got every day 1000+ login tries for my root user. An effective (but minimal) method to protect your machine is to run ssh on non-standard port. Any unused port will work but one above 1024 is preferable.

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A system may contain multiple physical CPUs (central processing unit), and can contain one or more cores (processors). Also, each core can have multiple threads, usually 2. (Hyper-threading Technology from Intel CPUs).

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