Java Learning notes--initial knowledge of Java

First knowledge of Java

Get this thick Java learning Note and open the table of contents: Introduction to the Java platform, from JDK to tde, objects of understanding, encapsulation, inheritance and polymorphism ... Looking at these indefinitely terms, I was intrigued and worried, so I began to walk into the world of Java.

The history of Java generation

Java comes from a program language written by Sun company called Green Project, and the world Wide Web is emerging, and Java applet is a representative of web interaction technology, especially for Internet application development.

features of the Java language

1. Object-oriented This is the most important feature of Java, the design of the Java language is completely object-oriented, it does not support the process-oriented program design technology like C language. Java supports code inheritance and reuse in both static and dynamic styles.

I have always been very vague about object-oriented meaning, I am here to know what is the object of the Internet? Everything can be seen as an object, and objects are everywhere. You can think of a tree as a special object class, and generally the tree is a very abstract class, because it's hard to find a tree that sums up all the trees. Therefore, in my garden, oak, I call it myoak; in your garden, tree, you call it Thatdarnedtree, and Generalsherrnan is a famous redwood. They are all special cases of trees, that is to say, oak, tree and redwood are the sub-categories of trees. Note that the class is introduced here as a specification for a collection of objects that describe a common attribute (specification). A class is a program segment that expresses a specification or template, which defines how a particular object is organized. A subclass is also a class that inherits all the attributes of the parent class and has its own special properties. Of course, the defined class should meet your needs, and it does not have an absolute framework. For a small problem, the tree class specification may contain only the types and heights of the trees.

2. Structural neutrality in order to build Java as a whole of the network, Java compiles its programs into an intermediate file format that is structurally neutral. The Java source program is compiled into a high-level machine-independent Byte-code format language that is designed to run on a virtual machine and is implemented by a machine-related run debugger.

Java data types, variables

The Java programming language defines eight basic data types, divided into four classes: integer classes (byte, short, int, long), text Class (char), floating-point class (double, float), and Logical Class (Boolean).

A variable (varialble) is a named memory area used to store Java program information, which is a meaningful piece of data. Declare the variable, that is to tell the JVM, I want to have a location, this position is called XXX name, what kind of data can be put.

commonly used operators in Java

There are five types of Java operators: arithmetic operators, assignment operators, relational operators, Boolean logical operators, bitwise operators. Bitwise operators have a shift operation in addition to a simple bitwise operation. A bitwise operation returns a Boolean value.

For Java learning, I am still in the initial stage, but I think the basic knowledge of learning to trace, to understand the nature of the problem, so as to extrapolate, from the point and the surface, for the abstract things specific, concrete things abstract, this is my next study in need of effort. In the future, I will be in the process of learning to do, try to write code, instead of holding a book to see on the line, really do the teacher in class, "Do the middle school."

Java Learning notes--initial knowledge of Java