Java Basic Knowledge Summary (absolute Classic) __java

Write code:

1, clear demand. What I'm going to do.

2, analysis of ideas. What am I going to do? 1,2,3.

3, determine the steps. What statements, methods, and objects are used in each part of the idea.

4, code implementation. Use the specific Java language code to reflect the idea.

Four points to learn new technology:

1, what the technology is.

2, what is the feature of the Technology (use note):

3, how the technology is used. Demo

4. When will the technology be used? Test

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One: Java Overview:

1991 Sun's James Gosling (James · Gauss Forest) and other people began to develop the name Oak language, hope to control embedded in the cable TV Exchange box, PDA and other microprocessors;

1994 renamed the Oak Language to Java;

Three technical architectures for Java:

Javaee:java Platform Enterprise Edition, develop the application in enterprise environment, mainly for Web program development;

Javase:java Platform Standard Edition, the completion of desktop application development, is the basis of the other two;

Javame:java Platform Micro Edition, the development of electronic consumer products and embedded devices, such as mobile phone procedures;

1,jdk:java Development Kit,java's development and running environment, Java development tools and JRE.

2,jre:java Runtime Environment,java The running environment of the program, Java runs the required class library +JVM (Java Virtual machine).

3, configure environment variables: Let the Java jdk\bin directory of tools, can run in any directory, because the tool is the directory told the system, when the tool used by the system to help us find the specified directory.

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, and then go to the path set in the paths below to find.

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

If you do not define an environment variable Classpath,java starts the JVM, it finds the class file to run in the current directory;

If Classpath is specified, the class file to run is found under the specified directory.

Will you also find it in the current directory. Two cases:

1): If the value of the classpath has a semicolon at the end, 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, in the specific path does not find the running class, no longer the current directory to find.

Usually do not specify a semicolon, if you do not find the specified directory to run the class file, the error, so you can debug the program.