First Java job

< p align = "center" > getting acquainted with Java jobs

Class, and this class must have the same name as the source file name.

< p class = "1" > II. Multiple choice questions

(3) Java compiles at one place and runs at multiple places, and C language compiles and runs multiple times

　　　　1. Path environment variable: it is used to specify the command search path. Execute the command under the I command line. For example, when javac compiles the Java program, it will look in the path specified by the path variable to see if the corresponding command program can be found. We need to add the bin directory under the JDK installation directory to the existing path variable. The bin directory contains frequently used executable files, such as javac / Java / Javadoc. After setting the path variable, we can execute javac / Java and other tools in any directory.

　　　　2. Classpath environment variable: it is used to specify the class search path. The prepared classes should be used on the premise that they can be found. The JVM uses classpath to find classes. We need to install DT in the Lib subdirectory under the JDK installation directory Jar and tools Jar is set in classpath. Of course, the current directory is "." Must also be added to the variable.