Java

Asynchronous execution with ExecutorService. Runnable, Callable, Future, CountDownLatch.

ExecutorService Build in API, which running of asynchronous tasks makes simple. Create it with factory method from Executors class: Assign a task in one of 3 ways: submit(task) – provide Runnable or Callable task as an argument. Returns Future invokeAny(taskList) – provide collection of Callable tasks. Tries to execute all tasks, returns response from one of successfully executed. invokeAll(taskList) –…

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Java

Java functional interface. Lambda, Consumer, Supplier, Predicate.

Functional interface – an interface with single abstract method. Optionally marked with @FunctionalInterface annotation.   Lambda – functional interface with a method, which receives and returns value   Supplier – function, which does not receive value, but returns one. Mostly used for lazy value generation.   Consumer – function, which receive value, but does not return. Mostly used for side…

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General

Some useful Docker stuff

Some common commands necessary to build and run own docker image in a container: Command Description Example docker pull [image_name] Pulls image from default docker registry: https://hub.docker.com/ docker pull ubuntu docker ps [options] List running containers. Add -a for all available container. docker ps -a docker container create [options] [image_name] [comand] Creates container with pulled image. Add –name to provide…

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Java

How to use Jetty to run Java web application locally?

Development of enterprise level web applications always cause some extra effort to setup various components locally. For example, if production environment runs big and robust Web Application server, like IBM WebSphere or Oracle WebLogic, you might don’t want to install and run it locally. Either for performance, configuration or licensing obstacles. There is a reasonable alternative to run and debug…

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Database

How to run Oracle SQLcl client directly as a Java class (skip sql.exe)?

Oracle SQL Developer Command Line (SQLcl) is a free command line interface for Oracle Database. It allows you to interactively or batch execute SQL and PL/SQL. SQLcl provides in-line editing, statement completion, and command recall for a feature-rich experience, all while also supporting your previously written SQL*Plus scripts. Here is what is said about this tool by Oracle. As an…

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Java

How to convert HTML to PDF in Java ?

There is so common requirement to generate PDF for some online content or reporting data. Also there is number of ways doing it. For example you could deliver it by leveraging headless browser (like Chrome or an older, already not supported but verified by time – PhantomJs) or use some dedicated back-end library. Differences between the latter are most likely…

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Linux

Common usages of grep and find in Linux

It is so common need to dig some info in Linux remote machines where you have just a terminal access. Effectiveness of searching might be crucial in finding necessary files and content. Here are couple of commands come to help as: grep – search in file contents find – search by file name It happens that sometimes quite difficult to…

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