1. Install J2SDK, I use the J2SDK-1_4_0-win.exe installation version, the installation directory is C: /J2SDK1.4.0; 2, in general, the path environment variable and the classpath environment variable is set, but if not , You need to manually set: Start - "My Computer -" Properties - "Advanced - Environment Variables - System Variables and add C: /J2SDK1.4.0/bin to the PATH variable, plus it to the ClassPath variable. 3, open the MS-DOS window, enter the Java and Javac commands, if it is valid, then the Java compilation execution environment installation configuration is successful. 4, in the e-plate root directory E: / down new text document, the content is as follows: // HelloWorld.java public class helloworld {public static void main (string args []) {system.out.println ("Hello World!") }} And saved as helloworld.java files, pay attention to the Java source file extension name is .java, and its file name must be the same as the public class name, the case is the same, for example, the class name here is HelloWorld, file name It is HelloWorld. 5. Go back to the MS-DOS window, enter Javac HelloWorld.java in E: /, you can find a new file helloworld.class. 6. Execute this Java program, enter Java HelloWorld, pay attention not to the extension. If this command causes the following error: Exception in thread "main" java.lang.noclassdeffounderror: HelloWorld then need to add parameters to the command (specify the class path as the current directory), which is java -classpath. HelloWorld, the program will correctly output Hello World!
