Tag | Description |
---|---|
options | Command line options. |
sourcefiles | One or more source files to be compiled (such as MyClass.java). |
@argfiles | One or more files that list source files. The -J options are not allowed in these files. |
There are two ways to pass source code file names to javac:
Tag | Description |
---|---|
o | For a small number of source files, simply list the file names on the command line. |
o | For a large number of source files, list the file names in a file, separated by blanks or line breaks. Then use the list file name on the javac command line, preceded by an @ character. |
Inner class definitions produce additional class files. These class files have names combining the inner and outer class names, such as MyClass$MyInnerClass.class.
You should arrange source files in a directory tree that reflects their package tree. For example, if you keep all your source files in /workspace, the source code for com.mysoft.mypack.MyClass should be in /workspace/com/mysoft/mypack/MyClass.java.
By default, the compiler puts each class file in the same directory as its source file. You can specify a separate destination directory with -d (see OPTIONS, below).
For example, when you subclass java.applet.Applet, you are also using Applets ancestor classes: java.awt.Panel, java.awt.Container, java.awt.Component, and java.awt.Object.
When the compiler needs type information, it looks for a source file or class file which defines the type. The compiler searches first in the bootstrap and extension classes, then in the user class path (which by default is the current directory). The user class path is defined by setting the CLASSPATH environment variable or by using the -classpath command line option. (For details, see Setting the Class Path.)
If you use the -sourcepath option, the compiler searches the indicated path for source files; otherwise the compiler searches the user class path both for class files and source files. You can specify different bootstrap or extension classes with the -bootclasspath and -extdirs options; see Cross-Compilation Options below.
A successful type search may produce a class file, a source file, or both. Here is how javac handles each situation:
Tag | Description |
---|---|
o | Search produces a class file but no source file: javac uses the class file. |
o | Search produces a source file but no class file: javac compiles the source file and uses the resulting class file. |
o |
Search produces both a source file and a class file:
javac determines whether the class file is out of date.
If the class file is out of date,
javac recompiles the source file
and uses the updated class file.
Otherwise,
javac just uses the class file.
By default, javac considers a class file out of date only if it is older than the source file. |
Tag | Description | ||||||||
---|---|---|---|---|---|---|---|---|---|
-classpath classpath | |||||||||
Sets the user class path, overriding the user class path in
the
CLASSPATH environment variable.
If neither
CLASSPATH or
-classpath is specified, the user class path consists of the
current directory.
See
Setting the Class Path for more details.
If the -sourcepath option is not specified, the user class path is searched for both source files and class files. | |||||||||
-Djava.ext.dirs=directories | |||||||||
Override the location of installed extensions. | |||||||||
-Djava.endorsed.dirs=directories | |||||||||
Override the location of endorsed standards path. | |||||||||
-d directory | |||||||||
Sets the destination directory for class files.
The destination directory must already exist; javac
will not create the destination directory.
If a class is part of a package,
javac puts the class file in a
subdirectory reflecting the package name, creating
directories as needed.
For example, if you specify
-d /home/myclasses and the class is called
com.mypackage.MyClass, then the class file is called
/home/myclasses/com/mypackage/MyClass.class. If -d is not specified, javac puts the class file in the same directory as the source file. Note: The directory specified by -d is not automatically added to your user class path. | |||||||||
-deprecation | |||||||||
Shows a description of each use or override of a deprecated member or class. Without -deprecation, javac shows the names of source files that use or override deprecated members or classes. -deprecation is shorthand for -Xlint:deprecation. | |||||||||
-encoding encoding | |||||||||
Sets the source file encoding name, such as EUCJIS/SJIS/ISO8859-1/UTF8. If -encoding is not specified, the platform default converter is used. | |||||||||
-g | Generates all debugging information, including local variables. By default, only line number and source file information is generated. | ||||||||
-g:none | Does not generate any debugging information. | ||||||||
-g:keyword-list | |||||||||
Generates only some kinds of debugging information, specified
by a comma separated list of keywords. Valid keywords are:
| |||||||||
-help | Prints a synopsis of standard options. | ||||||||
-nowarn | Disables warning messages. This has the same meaning as -Xlint:none. | ||||||||
-source release | |||||||||
Enables support for compiling source code containing assertions. The following values for release are allowed: |
Tag | Description |
---|---|
1.5 | he compiler accepts code containing generics and other language features introduced in JDK 1.5. The compiler defaults to the 1.5 behavior if the -source flag is not used. |
5 | Synonym for 1.5 |
1.4 | the compiler accepts code containing assertions, which were introduced in JDK 1.4. |
1.3 | the compiler does not support assertions, generics, or other language features introduced after JDK 1.3. |
Tag | Description | ||||||
---|---|---|---|---|---|---|---|
-sourcepath sourcepath | |||||||
Specify the source code path to search for class or interface
definitions.
As with the user class path, source path entries
are separated by colons
(:) and can be directories,
JAR archives, or
ZIP archives.
If packages are used, the local
path name within the directory or archive must reflect the
package name.
Note: Classes found through the classpath are subject to automatic recompilation if their sources are found.
|
Tag | Description | ||||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
-target version | |||||||||||||||
Generates class files that will work on
VMs with the specified version.
The default is to generate class files to be
compatible with 1.2
VMs, with one exception. When the -source 1.4 option is used, the default target is 1.4.
The versions supported by javac are:
| |||||||||||||||
-bootclasspath bootclasspath | |||||||||||||||
Cross-compiles against the specified set of boot classes. As with the user class path, boot class path entries are separated by colons (:) and can be directories, JAR archives, or ZIP archives. | |||||||||||||||
-cldc1.0 | Use to compile CLDC programs. The compiler generates stack maps making the use of the preverifier unnecessary. | ||||||||||||||
-extdirs directories | |||||||||||||||
Cross-compiles against the specified extension directories. Directories are a colon-separated list of directories. Each JAR archive in the specified directories is searched for class files. |
Tag | Description | |
---|---|---|
-Xbootclasspath/p:path | ||
Prepend to the bootstrap class path. | ||
--Xbootclasspath/a:path | ||
Append to the bootstrap class path. | ||
-Xbootclasspath/:path | ||
Override location of bootstrap class files. | ||
-Xlint | Enable all recommended warnings. In this release, all available warnings are recommended. | |
-Xlint:none | ||
Disable all warnings not mandated by the Java Language Specification. | ||
-Xlint:-xxx | ||
Disable warning xxx, where xxx is one of the warning names supported for -Xlint:xxx, below | ||
-Xlint:unchecked | ||
Give more detail for unchecked conversion warnings that are mandated by the Java Language Specification. | ||
-Xlint:path | ||
Warn about nonexistent path (classpath, sourcepath, etc) directories. | ||
-Xlint:serial | ||
Warn about missing serialVersionUID definitions on serializable classes. | ||
-Xlint:finally | ||
Warn about finally clauses that cannot complete normally. | ||
-lint:fallthrough | ||
Check switch blocks for fall-through cases and provide a
warning message for any that are
found. Fall-through cases are cases in a switch
block, other than the last case in the block,
whose code does not include a break statement,
allowing code execution to "fall through"
from that case to the next case. For example,
the code following the case 1 label in this
switch block does not contain a break statement:
| ||
If the -Xlint:fallthrough flag were used when compiling this code, the compiler would emit a warning about "possible fall-through into case," along with the line number of the case in question. | ||
-Xmaxerrors number | ||
Set the maximum number of errors to print. | ||
-Xmaxwarns number | ||
Set the maximum number of warnings to print. -Xstdout filename Send compiler messages to the named file. By default, compiler messages go to System.err. |
Tag | Description |
---|---|
-Joption | Pass option to the java launcher called by javac. For example, -J-Xms48m sets the startup memory to 48 megabytes. Although it does not begin with -X, it is not a standard option of javac. It is a common convention for -J to pass options to the underlying VM executing applications written in Java. |
An argument file can include javac options and source filenames in any combination. The arguments within a file can be space-separated or newline-separated. Filenames within an argument file are relative to the current directory, not the location of the argument file. Wildcards (*) are not allowed in these lists (such as for specifying *.java). Use of the @ character to recursively interpret files is not supported.
When executing javac, pass in the path and name of each argument file with the @ leading character. When javac encounters an argument beginning with the character @, it expands the contents of that file into the argument list.
C:> javac @argfile
This argument file could contain the contents of both files shown in the next example.
Create a file named options containing:
-d classes
-g
-sourcepath \java\pubs\ws\1.3\src\share\classes
Tag | Description | |
---|---|---|
Create a file named | ||
classes containing:
| ||
You would then run javac with:
| ||
|
% javac @path1/options @path2/classes
% ls
greetings/
% ls greetings
Hello.java
% cat greetings/Hello.java
package greetings;
public class Hello {
public static void main(String[] args) {
for (int i=0; i < args.length; i++) {
System.out.println("Hello " + args[i]);
}
}
}
% javac greetings/Hello.java
% ls greetings
Hello.class Hello.java
% java greetings.Hello World Universe Everyone
Hello World
Hello Universe
Hello Everyone
% ls
greetings/
% ls greetings
Aloha.java GutenTag.java Hello.java Hi.java
% javac greetings/*.java
% ls greetings
Aloha.class GutenTag.class Hello.class Hi.class
Aloha.java GutenTag.java Hello.java Hi.java
% pwd
/examples
% javac greetings/Hi.java
Since greetings.Hi refers to other classes in the greetings package, the compiler needs to find these other classes. The example above works, because our default user class path happens to be the directory containing the package directory. But suppose we want to recompile this file and not worry about which directory were in? Then we need to add /examples to the user class path. We can do this by setting CLASSPATH, but here well use the -classpath option.
% javac -classpath \examples /examples/greetings/Hi.java
If we change greetings.Hi again, to use a banner utility, that utility also needs to be accessible through the user class path.
% javac -classpath /examples:/lib/Banners.jar \
/examples/greetings/Hi.java
To execute a class in greetings, we need access both to greetings and to the classes it uses.
% java -classpath /examples:/lib/Banners.jar greetings.Hi
% ls
classes/ lib/ src/
% ls src
farewells/
% ls src/farewells
Base.java GoodBye.java
% ls lib
Banners.jar
% ls classes
% javac -sourcepath src -classpath classes:lib/Banners.jar \
src/farewells/GoodBye.java -d classes
% ls classes
farewells/
% ls classes/farewells
Base.class GoodBye.class
Note: The compiler compiled src/farewells/Base.java, even though we didnt specify it on the command line. To trace automatic compiles, use the -verbose option.
% javac -target 1.4 -bootclasspath jdk1.4.2/lib/classes.zip \
-extdirs "" OldCode.java
The -target 1.4 option ensures that the generated class files will be compatible with 1.4 VMs. BY default, javac compiles for 1.5.
The Java 2 SDks javac would also by default compile against its own bootstrap classes, so we need to tell javac to compile against JDK 1.4 bootstrap classes instead. We do this with -bootclasspath and -extdirs. Failing to do this might allow compilation against a Java 2 Platform API that would not be present on a 1.4 VM and would fail at runtime.
Tag | Description |
---|---|
The Java Extensions Mechanism @ | |
http://java.sun.com/j2se/1.5/docs/guide/extensions/index.html
|
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