• The three basic components of a Java program are comments, import
statements, and class declarations.
• AJava 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.
• Tocommand 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.
• Asingle 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.
• Asource file is compiled into a bytecode file by a Java compiler.
• AJava interpreter (also called a Java Virtual Machine) executes the bytecode.
• The standard classes introduced in this chapter are:
JFrame SimpleDateFormat
JOptionPane String
Date
• Table 2.2 lists the Java naming convention. (39.0K)