Java command-line compiler execution Program

Before you learn Java using the IDE, it is a good idea to use the command line Javac, Java to run a simple program, so you can familiarize yourself with the effect of package management on the path of the. class file.

Let's start by writing a simple code:

Package Com.csdn.lkasdolka;public class test_1{public    static void Main (string[] args) {for (int i = 0; i <; ++i) {    System.out.println (i);}}    }

Write well after saving for test_1.java,windows Environment Win+r Open command line, CD to Test_1.java file directory.

With the command

Compile the file, if the previous Java environment is configured, at this time in the command line to enter Dir we can see the directory is more than one Test_1.class file:

2014/10/06  16:23    <DIR>          2014/10/06  16:23    <DIR>          . 2014/10/06  16:23               454 test_1.class2014/10/06  16:09               173 Test_1.java               2 files            627 bytes               2 directories 13,711,450,112 bytes Available

Next use

Java test_1

An exception occurred while trying to run the bytecode file.

Exception in thread "main" java.lang.NoClassDefFoundError:test_1 (wrong name:cn/bupt/d10_1006_1/test_1) at JAVA.L Ang. Classloader.defineclass1 (Native Method) at Java.lang.ClassLoader.defineClass (classloader.java:800) at JAVA.S Ecurity. Secureclassloader.defineclass (secureclassloader.java:142) at Java.net.URLClassLoader.defineClass ( urlclassloader.java:449) at java.net.urlclassloader.access$100 (urlclassloader.java:71) at Java.net.URLClassL Oader$1.run (urlclassloader.java:361) at Java.net.urlclassloader$1.run (urlclassloader.java:355) at Java.secur ity. Accesscontroller.doprivileged (Native Method) at Java.net.URLClassLoader.findClass (urlclassloader.java:354) A T Java.lang.ClassLoader.loadClass (classloader.java:425) at Sun.misc.launcher$appclassloader.loadclass ( launcher.java:308) at Java.lang.ClassLoader.loadClass (classloader.java:358) at sun.launcher.launcherhelper.c Heckandloadmain (launcherhelper.java:482) 

This is because we set up a place in the beginning of the code

Com.csdn.lkasdolka

The package. A package is a mechanism for managing namespaces in Java. We need to manually create the Com\csdn\lkasdolka in the current folder and then cut the Test_1.class into the Com\csdn\lkasdolka\ directory.

At this time, the CD back to the original working directory (the parent directory of COM), the command line input

Java com.csdn.lkasdolka.test_1

Or

Java com/csdn/lkasdolka/test_1

You should be able to see the correct output:

C:\users\acer\desktop\technology\test_java>java com.csdn.lkasdolka.test_10123456789c:\users\acer\desktop\ Technology\test_java>java com/csdn/lkasdolka/test_10123456789

Summary:

1.javac is used to compile. java files to generate. class files (bytecode files), which Java uses to execute. class files, and to remove the. class suffix when executing.

2. If the package is defined in the source file, the. class file needs to be placed in the corresponding directory of the package definition, or the Java command will be noclassdeffounderror exception

The end~

(If there is an error, please correct it)

Java command-line compiler execution Program