Java is a programming language which is currently owned by Oracle.
Programming languages are the building blocks for communicating instructions to machines, without them the technology driven world we live in today wouldn’t exist.
Java is a general purpose high-level, object-oriented programming language.
Initially developed in 1991 under the name OAK, it was designed for handheld devices and set-top box, but with limited success the name was changed to Java and modified to be aimed at the then burgeoning World Wide Web.
Fast forward to today and Java is one of the most commonly used languages for developing and delivering content on the web. An estimated nine million Java developers use it and more than three billion mobile phones run it.
Java is an object-oriented language, which means that programmers define not only the data type of a data structure, but also the types of functions that can be applied to the data structure. It is similar in that way to C++ but has been simplified to eliminate language features that can cause common errors.
The aim of Java is to be easy to use, provide a high level of reliability and to also be secure. Security is built in as one of the foundations of the language due to it being designed for mobile devices that would be exchanging data across networks.
Where is Java most commonly used?
Java is free to download after it was released under the General Public License in 2007.
The general-purpose language is intended to let developers write once, run anywhere, meaning that compiled Java code can run on all platforms that support it without the need for recompilation.
Java is commonly used in Android apps and is also widely used in financial services by banks such as Barclays, Citigroup and others which use it for writing front and back office electronic trading systems, writing settlement and confirmation systems, data 
processing projects and more.
Popular big data technologies in Hadoop also use Java such as HBase, Accumulo, and ElasticSearch.
One of the reasons for Java’s success it is Rich API which provides for I/O, networking, utilities, XML, parsing and database connections, while open source libraries also ensure that it can be used pretty much everywhere.
