The three basic components of a Java program are comments, import statements, and class declarations.
A Java program must have one class designated as the main class. The designated main class must have the main method.
An object must be declared and created before we can use it.
To command an object or a class to perform a task, we send a message to it. We use the expression "calling a method" synonymously with "sending a message."
A single name can be used to refer to different objects (of the same class) at different times. An object with no reference will be returned to a system.
We follow the edit-compile-run cycle to execute programs.
A source file is compiled into a bytecode file by a Java compiler.
A Java interpreter (also called a Java Virtual Machine) executes the bytecode.
The standard classes introduced in this chapter are
