What are the Java essentials? You will learn how applications, applets, and servlets are similar and different, how to build a basic user interface that handles simple end user input, how to read data from and write data to files and databases, and how to send and receive data over the network.Which statement is essential in a Java program? Package Declaration Note that there can be only one package statement in a Java program. It must be defined before any class and interface declaration. It is necessary because a Java class can be placed in different packages and directories based on the module they are used.What are the basics of Java? Features of Java Simple: Java is a simple language because its syntax is simple, clean, and easy to understand. ... Object-Oriented: In Java, everything is in the form of the object. ... Robust: Java makes an effort to check error at run time and compile time.