201521123028 Java programming 1th Week of study summary

1. Summary of this week's study

Through this week's study:

1. Understand the history of Java (from oak to the Internet and evolve to the present)

2. The Java language features in comparison to the C language:

① compiles the source program into a structure-neutral intermediate file format. Run on a virtual machine (JVM) for cross-platform operation

② the error-prone areas such as pointer manipulation and memory management

③ provides a rich library of classes

3. Learn about JVM, JRE, JDK

4. Understand the basic structure of a Java program, can make up a simple Java program

2. Written work

Q1: Why are Java programs running across platforms? What are the steps to execute a Java program? (please write in your own language)

A:java can run across platforms because the program (. Class) does not deal directly with the platform, but with the virtual machine (JVM), so as long as the source program is compiled into a structurally neutral intermediate file format, the Java Runtime System (JRE) on the platform runs across the platform.

To execute a Java program: Compile the source code (. java file) from the compiler into a bytecode (. Class), then convert the JVM to the local machine code and then run it on the machine.

Q2: What is the difference between JDK?JDK,JRE,JVM?

A:JDK Full Name Java Development Kit, translated is Java development tools, is for Java developers to use a set of tools, including JAVAC,JAVAP and other tools. The JDK includes the JVM and its development environment and compilers.

The Jre,java runtime environment, the Java runtime environment, contains virtual machines that are intended for general users only.

Q3:java HelloWorld Command, what does this parameter refer to in HelloWorld? Is it a file name? What is the meaning of this command?

Refers to the class name, which is used to execute this class.

What is the use of Q4:path variables? What is the use of classpath variables?

The A:path variable is used to locate the running path of the program referred to by the PATH variable.

Classpath variables: Most tool programs, such as Javac, are written in Java and executed on top of the JVM, classpath variables are variables that are used to specify tools such as Javac (not quite understood, can be understood as the tool's run path?). )

Q5: What is the difference between writing a program in Java and running a program and running it with the C language, and the intermediate and target files that are generated?

A: the intermediate files (. java and. cpp) of the two represent different language types of files that need to be compiled before they can be run on the computer, and the target files (. class and. exe), both of which are executable files, are different kinds of files that are compiled by. Java and. cpp.

What are the 3 application versions of the Q6:java language? What is the relationship between versions?

A:java SE, Java EE, and Java ME.

Java SE is the foundation of the application platform, Java EE defines a series of services, APIs, protocols, etc., Java me for small digital device application development.

What is the difference between the q7:oracle JDK and the open JDK?

The A:open JDK is a development tool that is released after the Oracle JDK lacks a small number of closed-source features.

What are the main applications of Q8:java in these areas? What are your goals and expectations in this course?

A: Web-based major applications in Java Web, Java Enterprise-class applications.

Based on the mobile app on the Android system.

Goals and expectations: Understand how the Java platform Works, Master Java basic usage, and write Java applications.

3. Using the code cloud to manage Java code

201521123028 Java programming 1th Week of study summary