WHAT IS JAVA?
Java is a general purpose programming language designed with one mantra in mind—”write once, run anywhere.” Java applications are compiled into bytecode that can run on implementations of the Java Virtual Machine (JVM). JVM helps bridge the gap between source code and the 1s and 0s that the computer understands. Any machine that has the JVM installed can run Java. In web development, Java features most prominently as a server-side language and the programming language of choice for mobile apps on the Android platform. It also still has a decent presence on the front-end as a Java applet, although this is falling out of favor due to security concerns.
Alongside HTML and CSS,
Both languages require the developer to code in terms of objects and their relationships to one another. By extension this gives both languages access to techniques like inheritance, encapsulation, and polymorphism. Object-Oriented Programming (OOP).
You should consider Java if your project involves…
Big Data Analytics
General Purpose Programming of Hardware
Server-Side Technologies like Apache, JBoss, Geronimo, GlassFish, etc.
Dynamic single page applications (SPAs)
Front-End technologies like jQuery, AngularJS, Backbone.js, Ember.js, ReactJS etc.
Server-Side technologies like Node.js, MongoDB, Express.js, etc.
Mobile App Development through PhoneGap, React Native, etc.
Keep in mind that neither list is extensive, these are only meant as a starting point to help you get a feel for what you can expect and what keywords you can use to assess the best language for your needs.