How to use the javac command, want to compile hello.java to hello.class, the file content is as follows:
How to introduce other packages, the directory structure is as follows
It's a mistake for me to run like this:
e:\icenew2\hellotest>javac -sourcepath src hello.java
It's wrong to run like this ： javac -cp "src\com\zeroc\Ice*.class" hello.java
We can use the wildcard character *:
javac -cp *; BackBenchers.java
Specifying destination directory:
javac -d classes backbenchers.java
Note: The compiler will complain if the specified directory does not exist, and it won’t create one.
If the source file is under a package, the compiler will create package structure in the destination directory.
Specifying source path directory:
javac -sourcepath src BackBenchers.java
Related
The problem
This is a problem I just faced using makefile in java, on Windows.
I wanted to set up my classpath with multiple path (libraries, etc.). The new command work by hands, but not from the makefile which throws me this error :
javac : no source files
Example
Let's say I have this makefile :
JFLAGS = -g
JARFLAGS = -cvfm
CLASSPATH = ./bin
LIBS = C:/java/lib/mylib.jar
SOURCEPATH = ./src/client
compileAll:
javac $(JFLAGS) -d $(CLASSPATH) -cp $(CLASSPATH)\;$(LIBS) $(SOURCEPATH )/*.java
jar $(JARFLAGS) app.jar bin/client/MANIFEST.MF bin/client/*.class
So the command line to compile the project is :
javac -g -d ./bin -cp ./bin;C:/java/libs/lib.jar ./src/client/*.java
It works well.
The class files goes to ./bin directory. It imports classes from ./bin and the lib.jar library. And it compliles all the source files from the ./src/client directory.
This command works perfectly by hands, but no from the makefile which doesn't compile anything.
Thanks to my text editor which colored the ';' character, I understood that I just needed to escape (disable) the ';' character by using a '\' :
javac -g -d ./bin -cp ./bin\;C:/java/libs/lib.jar ./src/client/*.java
Now, it works well from makefile !
I believe this is how I can compile and run a file that uses external library. I'm using Windows.
top level directory
|
|-log4-1.2.17.jar
|-MyApp.java
|-com
|-foo
|-Bar.java
Compiling
javac -cp log4j-1.2.17.jar;. com\foo\Bar.java
javac -cp log4j-1.2.17.jar;"com\foo";. MyApp.java
Executing
java -cp log4j-1.2.17.jar;"com\foo";. MyApp
Compiling itself failed.
simple batch script, for compiling all your project
set COMPILED_CLASSES=.\
set TEMP_FILE=temp
dir .\*.java /s /B > %TEMP_FILE%
javac -classpath log4j-1.2.17.jar;%COMPILED_CLASSES% -d %COMPILED_CLASSES% #%TEMP_FILE%
rm %TEMP_FILE%
add it to top level dir and run
EDIT
step by step
javac ./com/foo/Bar.java -classpath log4j-1.2.17.jar
next
javac ./MyApp.java -classpath log4j-1.2.17.jar;./
run
java -classpath log4j-1.2.17.jar;./ MyApp
Include current directory in java classpath
java -cp log4j-1.2.17.jar;. MyApp
Why do you have to include current directory:
The default class path is the current directory. Setting the CLASSPATH variable or using the -classpath command-line option overrides that default, so if you want to include the current directory in the search path, you must include "." in the new settings.
Y need to include the local directory. If you want to do it in the current directory it would be something like:
javac -cp .;log4j-1.2.17.jar Bar
I have the .java file on the current working directory but javac reports:
javac: no source files
Usage: javac <options> <source files>
use -help for a list of possible options
I'm working on ubuntu.
From your comment above, it looks like you tried:
javac -cp .;lib.jar a.java on your Ubuntu system. The CLASSPATH separator is : on Unix systems and ; on Windows.
Ubuntu considered the command up to the ;, java -cp . and thus gave the message.
javac -cp .:lib.jar a.java should compile fine.
For anyone who is using powersehll on windows use CLASSPATH separator : instead of ;
I tried a similar thing and found that you need to mention the absolute path when you are using the
-cp and -d option with javac like this
javac -cp 'ur location of jars & files'; -d 'location to add your classes to' 'absolute path of file'
eg:
javac -cp C:\home\lib\mywork; -d c:\home\classes c:\home\files*.java
for javac, there are options and arguments
arg: it takes argument as path of source file
options: we require for basic compilation
-sourcepath: the path of dependent source files
-d: directory path of output classes
javac -sourcepath './src' -d './bin' -verbose './src/App.java'
I'm writing a makefile that compiles a .java file in a different directory, and then I want to run it, without changing directories. I want to do something along the lines of:
$(SQM_JAVA_TOOL_DONE) : $(SQM_JAVA_TOOL)
$(shell cd /home_dir)
javac myjavafile.java
java myjavafile
where the Java file is /home/myjavafile.java, and the makefile isn't running from /home.
How can I do this?
I might be misunderstanding the question, but you can compile with
javac /home/MyJavaFile.java
This will create MyJavaFile.class in /home
You can then run it by including /home on the classpath. e.g.
java -cp /home MyJavaFile
If you want to generate the class file in a different directory then you can use the -d option to javac.
Use the -d command line parameter with javac to tell it what directory you'd like to store the compiled class files in. Then, to run the program, simply include this directory in the classpath:
javac -d some/directory myjavafile.java
java -cp some/directory myjavafile
Just to add to the existing answers, you may want the --source-path flag:
--source-path <path>, -sourcepath <path>
Specify where to find input source files
I believe this effectively sets the package root javac will compile from (i.e. <path> will be stripped from the expected package name of the files). It's still necessary to enumerate the files to compile, and this should still be relative to the current working directory, not the path passed to --source-path.
For example, to compile and run from a project's root where source is stored in src/ and you want it build in bin/:
$ javac --source-path src -d bin src/mypackage/*.java
$ java -cp bin mypackage.Main
This works even from directories elsewhere in the filesystem, e.g.:
$ javac --source-path /some/absolute/path/src -d /some/absolute/path/bin /some/absolute/path/
$ java -cp /some/absolute/path/bin mypackage.Main
I am using VS Code and installed java and code runner extensions. When I created new java project using the extension, it was creating the .class file in src instead of bin. To solve the issue I opened settings.json file from File > Preferences > Settings and searched for "settings" (or "code-runner"). Then I added following lines in that file.
"code-runner.executorMap": {
"java": "cd \"$workspaceRoot\\\" && javac --source-path src -d bin src\\$fileName && java -cp bin $fileNameWithoutExt",
}
If you don`t want to see the command that runs before code file then add these lines instead:
"code-runner.clearPreviousOutput": true,
"code-runner.showExecutionMessage": false,
"code-runner.executorMap": {
"java": "there is && clear added in the execution paramater"
"java": "cd \"$workspaceRoot\\\" && javac --source-path src -d bin src\\$fileName && clear && java -cp bin $fileNameWithoutExt",
}
I hope this finds someone with similar issue.
I'm puzzled by the process of running java programs, maybe you can help.
I have several .java files in ~/working_dir/org/project/ that have main functions, and I want to package them in a jar to run them. I do:
cd ~/working_dir/org/projectname
javac -classpath $CLASSPATH *.java
cd ~/working_dir/
jar cf myjar.jar org/
And then try to run one of the classes in the jar by doing:
java -cp myjar.jar org.project.SomeClass
and get
Exception in thread "main" java.lang.NoClassDefFoundError: org/project/SomeClass
Could not find the main class: org.project.SomeClass
What do I do wrong? The classes compile without any errors, and jar tf myjar.jar shows that they're indeed there. As far as I know I don't need to create a Manifest file because I provide the class from which I want to run the main function at runtime - or am I wrong here?
Help much appreciated!
If the exploded jar org/project/SomeClass is beneath your current working dir:
/ <- you are here
+---/org
|
+-----/project
|
+--------SomeClass.class
try java -cp . org.project.SomeClass instead
First of all, note that if you simply do
javac org/project/SomeClass.java
the class file will end up right beside the .java file which makes it tricky to include only .class-files in the jar. I suggest you use the -d option to specify destination directory:
javac -d bin org/project/SomeClass.java
Have a look at the following bash-session for details to get it working:
A listing of the source directory:
user#host:/working_dir/src$ ls -R
.:
org
./org:
projectname
./org/projectname:
SomeClass.java
The SomeClass.java file:
user#host:/working_dir/src$ cat org/projectname/SomeClass.java
package org.project;
public class SomeClass {
public static void main(String[] args) {
System.out.println("Hello World");
}
}
Compile it (with target directory ../bin)
user#host:/working_dir/src$ javac org/projectname/SomeClass.java -d ../bin
List the result and make sure you got the directories right:
user#host:/working_dir/src$ cd ../bin/
user#host:/working_dir/bin$ ls -R
.:
org
./org:
project
./org/project:
SomeClass.class
Create the jar file:
user#host:/working_dir/bin$ jar cf myjar.jar org
Make sure you got the directories right and didn't accidentally include the "bin" directory:
user#host:/working_dir/bin$ jar tf myjar.jar
META-INF/
META-INF/MANIFEST.MF
org/
org/project/
org/project/SomeClass.class
Launch the main method:
user#host:/working_dir/bin$ java -cp myjar.jar org.project.SomeClass
Hello World
user#host:/working_dir/bin$