Java source program (. Java file) -java bytecode file (. Class files)-bytecode files are loaded into java virtual machine (JVM) by interpreter (java.exe)-bytecode files (. Class) will be executed in the Java virtual machine.
The basic package of Java
java.lang？ It includes: interface: comparable, clonable, operational, etc. Class: Eight basic data types encapsulate classes, such as Byte, Short, Integer, Long, Boolean, Character, Float, Double and so on.
Extended data
Java is an object-oriented language. For programmers, this means focusing on data and the methods of manipulating data, rather than thinking strictly according to the process. Data and methods together describe the state and behavior of an object. Every object is an encapsulation of its state and behavior.
Classes are arranged according to a certain system and hierarchy, so that subclasses can inherit the behavior of superclasses. There is a root class in this class hierarchy, which is a class with general behavior. Java programs are organized by classes.
Java also includes a set of extended classes, which form various packages that users can use in their own programs.
For example, Java provides a class (java.awt package) for generating graphic user interface module, where awt is the abbreviation of abstract windowing toolkit, a class for processing input and output (java.io package) and a class for supporting network functions (java.awt package).
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