First day of basic Java learning

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Write code:

1, clear demand. What needs do I need to fulfill?

2, analysis of ideas. How do I need to fulfill my needs?

3, determine the steps. What statements, methods, objects do I need to use for each part of my train of thought?

4, the code implementation. Use code to express my ideas.

PS: Watch every day, go forward every day ...

================ Daily must-read ====================

Java Overview:

1. What is Java?

Java is an object-oriented programming language, not only absorbs the various advantages of the C + + language, but also rejects the difficult to understand C + + inheritance, pointers and other concepts, so the Java language has a powerful and easy to use two features. As the representative of static object-oriented programming language, the Java language implements the object-oriented theory, which allows programmers to do complex programming in an elegant way.

Java has the features of simplicity, object-oriented, distributed, robustness, security, platform independence and portability, and multithreading dynamics. Java can write desktop applications, Web applications, distributed systems, and embedded system applications.

2. A brief history of Java?

Java was developed by James Gosling in a team led by Sun. (2010 Sun Company was acquired by Oracle.) Java, originally known as Oak, was designed for embedded chips in consumer electronics in the 1991.

In the summer of 1992, when the Oak language was successfully developed, the researchers demonstrated to hardware manufacturers the green operating system, Oak's programming language, class library, and its hardware to persuade them to use the oak language to produce hardware chips, but the hardware makers did not have a great deal of enthusiasm. Because they believe that the risk of producing hardware products is too high for everyone to know about the oak language, and that the oak language is not able to enter the market because of lack of hardware support, and is shelved.

In July 1994, after a three-day discussion, the team decided to change the goal again, and this time they decided to apply the technology to the World Wide Web.

Renamed Java in 1995 and redesigned to develop Web applications.

In January 1996, Sun released the first Java Development Kit (JDK 1.0), an important milestone in the Java development process.

In June 1999, Sun released its second-generation Java platform, including J2ME, J2SE, and EE. The release of the Java 2 platform is one of the most important milestones in the Java development process, marking the beginning of the popularity of Java applications.

April 27, 1999, hotspot virtual Machine released. The hotspot virtual machine was released as an add-on to JDK 1.2, and later it became the default virtual machine for all versions of JDK 1.3 and later Sun JDK.

In May 2000, JDK1.3, JDK1.4 and j2se1.3 were released successively.

In June 2005, at the Java One conference, Sun released the Java SE 6. At this point, various versions of Java have been renamed, and the number 2 has been canceled, as the JAVAEE,J2SE renamed Javase,j2me renamed to Javame.

3, Java programming development?

1) Programming Environment: (JVM, JRE, JDK)

Jvm:java virtual machines; (Java VM)

Jre:java runtime Environment; (Java Runtime Environment, including Java Virtual machine, Java base Class library)

Jdk:java Development Kit; (Java Development Kit, including Jre,java tools)

2) Development tools:

Eclipse: An open-source, Java-based, extensible development platform.

NetBeans: Open source Java integrated development environment for a variety of client and Web applications.

IntelliJ idea: It has very good function in code automatic prompt, code analysis and so on.

MyEclipse: A commercial software developed by genuine company, is a widely used Java application integration development environment.

EditPlus: If the Java compiler "Javac" and the Interpreter "Java" are properly configured, you can execute the Java program directly using EditPlus compilation.

4, Java language features?

Java has the features of simplicity, object-oriented, distributed, robustness, security, platform independence and portability, and multithreading dynamics.

5. What is the use of the Java language?

Java can write desktop applications, Web applications, distributed systems, and embedded system applications.

6. How does the Java language work?

Consists of four aspects:

(1) Java programming language (2) Java class file format (3) Java Virtual machine

(4) Java application interface

7. Configure environment variables?

Meaning: Let the tools in the Java Jdk\bin directory run in any directory, because the directory where the tool is located is told to the system, and when the tool is used, the system helps us to find the specified directory.

1) Configuration of environment variables:

"1" Permanent configuration mode: java_home=% installation path%\JAVA\JDK
Path=%java_home%\bin

"2" Temporary configuration mode: Set path=%path%; C:\Program Files\java\jdk\bin
Features: The system defaults to the current path to find the program to execute, if not, then go to the path set in the paths to find.
2) classpath configuration:

"1" Permanent configuration mode: classpath=.; C:\;e:\

"2" Temporary configuration mode: Set classpath=.; C:\;e:\

Note: When defining CLASSPATH environment variables, you need to be aware of the situation
If you do not define an environment variable Classpath,java starts the JVM, it looks for the class file to run under the current directory;
If Classpath is specified, the class file to be run is looked up under the specified directory.
Will you find it in the current directory? Two cases:
1) If there is a semicolon at the end of the value of Classpath, the running class is not found in the specific path and will be found again by default in the current directory.
2) If the value of classpath results in no semicolon, the running class is not found in the specific path, and no longer is found in the current directory.
Generally do not specify a semicolon, if not found in the specified directory to run the class file, the error, so you can debug the program.

8. What do javac commands and Java commands do?

You know that Java is divided into two parts: one is compile, one is run.
Javac: is responsible for the compilation of the part, when the execution of Javac, will start the Java compiler program. Compiles a. java file with the specified extension. Generates bytecode files that the JVM can recognize. This is the class file, which is Java's running program.
Java: The part responsible for running. The JVM is started. Load the class library that is required by the runtime and execute it on a class file.
A file to be executed must have a starting point for execution, and this starting point is the main function.

First day of basic Java learning