1javac(1) General Commands Manual javac(1)
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6 javac - Java programming language compiler
7
9 javac [ options ] [ sourcefiles ] [ @argfiles ]
10 Arguments may be in any order.
13 options
15 Command-line options.
16 sourcefiles
18 One or more source files to be compiled (such as
19 MyClass.java).
20 @argfiles
22 One or more files that lists options and source files. The -J
23 options are not allowed in these files.
24
27 The javac tool reads class and interface definitions, written in the
28 Java programming language, and compiles them into bytecode class files.
29 There are two ways to pass source code filenames to javac:
31 o For a small number of source files, simply list the file names on
33 the command line.
34 o For a large number of source files, list the file names in a file,
36 separated by blanks or line breaks. Then use the list file name on
37 the javac command line, preceded by an @ character.
38 Source code file names must have .java suffixes, class file names must
41 have .class suffixes, and both source and class files must have root
42 names that identify the class. For example, a class called MyClass
43 would be written in a source file called MyClass.java and compiled into
44 a bytecode class file called MyClass.class.
45 Inner class definitions produce additional class files. These class
47 files have names combining the inner and outer class names, such as
48 MyClass$MyInnerClass.class.
49 You should arrange source files in a directory tree that reflects their
51 package tree. For example, if you keep all your source files in
52 /workspace, the source code for com.mysoft.mypack.MyClass should be in
53 /workspace/com/mysoft/mypack/MyClass.java.
54 By default, the compiler puts each class file in the same directory as
56 its source file. You can specify a separate destination directory with
57 -d (see Options, below).
58
60 When compiling a source file, the compiler often needs information
61 about a type whose definition did not appear in the source files given
62 on the command line. The compiler needs type information for every
63 class or interface used, extended, or implemented in the source file.
64 This includes classes and interfaces not explicitly mentioned in the
65 source file but which provide information through inheritance.
66 For example, when you subclass java.applet.Applet, you are also using
68 Applet's ancestor classes: java.awt.Panel, java.awt.Container,
69 java.awt.Component, and java.lang.Object.
70 When the compiler needs type information, it looks for a source file or
72 class file which defines the type. The compiler searches for class
73 files first in the bootstrap and extension classes, then in the user
74 class path (which by default is the current directory). The user class
75 path is defined by setting the CLASSPATH environment variable or by
76 using the -classpath command line option. (For details, see Setting the
77 Class Path).
78 If you set the -sourcepath option, the compiler searches the indicated
80 path for source files; otherwise the compiler searches the user class
81 path for both class files and source files.
82 You can specify different bootstrap or extension classes with the
84 -bootclasspath and -extdirs options; see Cross-Compilation Options
85 below.
86 A successful type search may produce a class file, a source file, or
88 both. Here is how javac handles each situation:
89 o Search produces a class file but no source file: javac uses the
91 class file.
92 o Search produces a source file but no class file: javac compiles
94 the source file and uses the resulting class file.
95 o Search produces both a source file and a class file: javac deter‐
97 mines whether the class file is out of date. If the class file is
98 out of date, javac recompiles the source file and uses the updated
99 class file. Otherwise, javac just uses the class file.
100 javac considers a class file out of date only if it is older than
102 the source file.
103 Note: javac can silently compile source files not mentioned on the
106 command line. Use the -verbose option to trace automatic compilation.
107
109 The compiler has a set of standard options that are supported on the
110 current development environment and will be supported in future
111 releases. An additional set of non-standard options are specific to the
112 current virtual machine and compiler implementations and are subject to
113 change in the future. Non-standard options begin with -X.
114 Standard Options
116 -classpath classpath
117 Set the user class path, overriding the user class path in the
118 CLASSPATH environment variable. If neither CLASSPATH or
119 -classpath is specified, the user class path consists of the
120 current directory. See Setting the Class Path for more
121 details.
122 If the -sourcepath option is not specified, the user class path
124 is searched for both source files and class files.
125 As a special convenience, a class path element containing a base‐
127 name of * is considered equivalent to specifying a list of all
128 the files in the directory with the extension .jar or .JAR (a
129 java program cannot tell the difference between the two invoca‐
130 tions).
131 For example, if directory foo contains a.jar and b.JAR, then the
132 class path element foo/* is expanded to a A.jar:b.JAR, except
133 that the order of jar files is unspecified. All jar files in the
134 specified directory, even hidden ones, are included in the list.
135 A classpath entry consisting simply of * expands to a list of all
136 the jar files in the current directory. The CLASSPATH environment
137 variable, where defined, will be similarly expanded. Any class‐
138 path wildcard expansion occurs before the Java virtual machine is
139 started -- no Java program will ever see unexpanded wildcards
140 except by querying the environment. For example; by invoking Sys‐
141 tem.getenv("CLASSPATH").
142 -Djava.ext.dirs=directories
144 Override the location of installed extensions.
145 -Djava.endorsed.dirs=directories
147 Override the location of endorsed standards path.
148 -d directory
150 Set the destination directory for class files. The destination
151 directory must already exist; javac will not create the desti‐
152 nation directory. If a class is part of a package, javac puts
153 the class file in a subdirectory reflecting the package name,
154 creating directories as needed. For example, if you specify -d
155 /home/myclasses and the class is called com.mypackage.MyClass,
156 then the class file is called /home/myclasses/com/mypack‐
157 age/MyClass.class.
158 If -d is not specified, javac puts the class file in the same
160 directory as the source file.
161 Note: The directory specified by -d is not automatically added
163 to your user class path.
164 -deprecation
166 Show a description of each use or override of a deprecated
167 member or class. Without -deprecation, javac shows the names
168 of source files that use or override deprecated members or
169 classes. -deprecation is shorthand for -Xlint:deprecation.
170 -encoding encoding
172 Set the source file encoding name, such as EUC-JP and UTF-8..
173 If -encoding is not specified, the platform default converter
174 is used.
175 -g Generate all debugging information, including local variables.
177 By default, only line number and source file information is
178 generated.
179 -g:none
181 Do not generate any debugging information.
182 -g:{keyword list}
184 Generate only some kinds of debugging information, specified
185 by a comma separated list of keywords. Valid keywords are:
186 source
188 Source file debugging information
189 lines
191 Line number debugging information
192 vars
194 Local variable debugging information
195 -help
197 Print a synopsis of standard options.
198 -nowarn
200 Disable warning messages. This has the same meaning as
201 -Xlint:none.
202 -source release
204 Specifies the version of source code accepted. The following
205 values for release are allowed:
206 1.3
208 The compiler does not support assertions, generics, or
209 other language features introduced after JDK 1.3.
210 1.4
212 The compiler accepts code containing assertions, which were
213 introduced in JDK 1.4.
214 1.5
216 The compiler accepts code containing generics and other
217 language features introduced in JDK 5. This is the default.
218 5 Synonym for 1.5
220 Note: No language changes were introduced in JDK 6, so the values
221 1.6 and 6 are not valid.
222 -sourcepath sourcepath
224 Specify the source code path to search for class or interface
225 definitions. As with the user class path, source path entries
226 are separated by colons (:) and can be directories, JAR ar‐
227 chives, or ZIP archives. If packages are used, the local path
228 name within the directory or archive must reflect the package
229 name.
230 Note: Classes found through the classpath are subject to auto‐
232 matic recompilation if their sources are found.
233 -verbose
235 Verbose output. This includes information about each class
236 loaded and each source file compiled.
237 -X Display information about non-standard options and exit.
239 Cross-Compilation Options
242 By default, classes are compiled against the bootstrap and extension
243 classes of the platform that javac shipped with. But javac also sup‐
244 ports cross-compiling, where classes are compiled against a boot‐
245 strap and extension classes of a different Java platform implementa‐
246 tion. It is important to use -bootclasspath and -extdirs when
247 cross-compiling; see Cross-Compilation Example below.
248 -target version
250 Generate class files that target a specified version of the
251 VM. Class files will run on the specified target and on later
252 versions, but not on earlier versions of the VM. Valid targets
253 are 1.1 1.2 1.3 1.4 1.5 (also 5) and 1.6 (also 6).
254 The default for -target depends on the value of -source:
256 o If -source is not specified, the value of -target is 1.6
258 o If -source is 1.3, the value of -target is 1.1
260 o For all other values of -source, the value of -target is the
262 value of -source.
263 -bootclasspath bootclasspath
265 Cross-compile against the specified set of boot classes. As
266 with the user class path, boot class path entries are sepa‐
267 rated by colons (:) and can be directories, JAR archives, or
268 ZIP archives.
269 -extdirs directories
271 Cross-compile against the specified extension directories.
272 Directories is a colon-separated list of directories. Each JAR
273 archive in the specified directories is searched for class
274 files.
275 Non-Standard Options
278 -Xbootclasspath/p:path
279 Prepend to the bootstrap class path.
280 -Xbootclasspath/a:path
282 Append to the bootstrap class path.
283 -Xbootclasspath/:path
285 Override location of bootstrap class files.
286 -Xlint
288 Enable all recommended warnings. In this release, all avail‐
289 able warnings are recommended.
290 -Xlint:none
292 Disable all warnings not mandated by the Java Language Speci‐
293 fication.
294 -Xlint:-xxx
296 Disable warning xxx, where xxx is one of the warning names
297 supported for -Xlint:xxx, below
298 -Xlint:unchecked
300 Give more detail for unchecked conversion warnings that are
301 mandated by the Java Language Specification.
302 -Xlint:path
304 Warn about nonexistent path (classpath, sourcepath, etc)
305 directories.
306 -Xlint:serial
308 Warn about missing serialVersionUID definitions on serializ‐
309 able classes.
310 -Xlint:finally
312 Warn about finally clauses that cannot complete normally.
313 -Xlint:fallthrough
315 Check switch blocks for fall-through cases and provide a warn‐
316 ing message for any that are found. Fall-through cases are
317 cases in a switch block, other than the last case in the
318 block, whose code does not include a break statement, allowing
319 code execution to "fall through" from that case to the next
320 case. For example, the code following the case 1 label in this
321 switch block does not contain a break statement:
322 switch (x) {
325 case 1:
326 System.out.println("1");
327 // No break; statement here.
328 case 2:
329 System.out.println("2");
330 }
331 If the -Xlint:fallthrough flag were used when compiling this
332 code, the compiler would emit a warning about "possible
333 fall-through into case," along with the line number of the case
334 in question.
335 -Xmaxerrors number
337 Set the maximum number of errors to print.
338 -Xmaxwarns number
340 Set the maximum number of warnings to print.
341 -Xstdout filename
343 Send compiler messages to the named file. By default, compiler
344 messages go to System.err.
345 The -J Option
348 -Joption
349 Pass option to the java launcher called by javac. For example,
350 -J-Xms48m sets the startup memory to 48 megabytes. Although it
351 does not begin with -X, it is not a `standard option' of
352 javac. It is a common convention for -J to pass options to the
353 underlying VM executing applications written in Java.
354 Note: CLASSPATH, -classpath, -bootclasspath, and -extdirs do
356 not specify the classes used to run javac. Fiddling with the
357 implementation of the compiler in this way is usually pointless
358 and always risky. If you do need to do this, use the -J option to
359 pass through options to the underlying java launcher.
360
363 To shorten or simplify the javac command line, you can specify one or
364 more files that themselves contain arguments to the javac command
365 (except -J options). This enables you to create javac commands of any
366 length on any operating system.
367 An argument file can include javac options and source filenames in any
369 combination. The arguments within a file can be space-separated or new‐
370 line-separated. If a filename contains embedded spaces, put the whole
371 filename in double quotes.
372 Filenames within an argument file are relative to the current direc‐
374 tory, not the location of the argument file. Wildcards (*) are not
375 allowed in these lists (such as for specifying *.java). Use of the '@'
376 character to recursively interpret files is not supported. The -J
377 options are not supported because they are passed to the launcher,
378 which does not support argument files.
379 When executing javac, pass in the path and name of each argument file
381 with the '@' leading character. When javac encounters an argument
382 beginning with the character `@', it expands the contents of that file
383 into the argument list.
384 Example - Single Arg File
386 You could use a single argument file named "argfile" to hold all javac
387 arguments:
388 C:> javac @argfile
390 This argument file could contain the contents of both files shown in
393 the next example.
394 Example - Two Arg Files
396 You can create two argument files -- one for the javac options and the
397 other for the source filenames: (Notice the following lists have no
398 line-continuation characters.)
399 Create a file named "options" containing:
401 -d classes
403 -g
404 -sourcepath \java\pubs\ws\1.3\src\share\classes
405 Create a file named "classes" containing:
408 MyClass1.java
410 MyClass2.java
411 MyClass3.java
412 You would then run javac with:
415 % javac @options @classes
417 Example - Arg Files with Paths
420 The argument files can have paths, but any filenames inside the files
421 are relative to the current working directory (not path1 or path2):
422 % javac @path1/options @path2/classes
424
427 The com.sun.tools.javac.Main class provides two static methods to
428 invoke the compiler from a program:
429 public static int compile(String[] args);
431 public static int compile(String[] args, PrintWriter out);
432 The args parameter represents any of the command line arguments that
435 would normally be passed to the javac program and are outlined in the
436 above Synopsis section.
437 The out parameter indicates where the compiler's diagnostic output is
439 directed.
440 The return value is equivalent to the exit value from javac.
442 Note that all other classes and methods found in a package whose name
444 starts with com.sun.tools.javac (informally known as sub-packages of
445 com.sun.tools.javac) are strictly internal and subject to change at any
446 time.
447
449 Compiling a Simple Program
450 One source file, Hello.java, defines a class called greetings.Hello.
451 The greetings directory is the package directory both for the source
452 file and the class file and is off the current directory. This
453 allows us to use the default user class path. It also makes it
454 unnecessary to specify a separate destination directory with -d.
455 % ls
457 greetings/
458 % ls greetings
459 Hello.java
460 % cat greetings/Hello.java
461 package greetings;
462 public class Hello {
464 public static void main(String[] args) {
465 for (int i=0; i < args.length; i++) {
466 System.out.println("Hello " + args[i]);
467 }
468 }
469 }
470 % javac greetings/Hello.java
471 % ls greetings
472 Hello.class Hello.java
473 % java greetings.Hello World Universe Everyone
474 Hello World
475 Hello Universe
476 Hello Everyone
477 Compiling Multiple Source Files
480 This example compiles all the source files in the package greetings.
481 % ls
483 greetings/
484 % ls greetings
485 Aloha.java GutenTag.java Hello.java Hi.java
486 % javac greetings/*.java
487 % ls greetings
488 Aloha.class GutenTag.class Hello.class Hi.class
489 Aloha.java GutenTag.java Hello.java Hi.java
490 Specifying a User Class Path
494 Having changed one of the source files in the previous example, we
495 recompile it:
496 % pwd
498 /examples
499 % javac greetings/Hi.java
500 Since greetings.Hi refers to other classes in the greetings package,
503 the compiler needs to find these other classes. The example above
504 works, because our default user class path happens to be the direc‐
505 tory containing the package directory. But suppose we want to recom‐
506 pile this file and not worry about which directory we're in? Then we
507 need to add /examples to the user class path. We can do this by set‐
508 ting CLASSPATH, but here we'll use the -classpath option.
509 % javac -classpath /examples /examples/greetings/Hi.java
511 If we change greetings.Hi again, to use a banner utility, that util‐
514 ity also needs to be accessible through the user class path.
515 % javac -classpath /examples:/lib/Banners.jar \
517 /examples/greetings/Hi.java
518 To execute a class in greetings, we need access both to greetings
521 and to the classes it uses.
522 % java -classpath /examples:/lib/Banners.jar greetings.Hi
524 Separating Source Files and Class Files
527 It often makes sense to keep source files and class files in sepa‐
528 rate directories, especially on large projects. We use -d to indi‐
529 cate the separate class file destination. Since the source files are
530 not in the user class path, we use -sourcepath to help the compiler
531 find them.
532 % ls
534 classes/ lib/ src/
535 % ls src
536 farewells/
537 % ls src/farewells
538 Base.java GoodBye.java
539 % ls lib
540 Banners.jar
541 % ls classes
542 % javac -sourcepath src -classpath classes:lib/Banners.jar \
543 src/farewells/GoodBye.java -d classes
544 % ls classes
545 farewells/
546 % ls classes/farewells
547 Base.class GoodBye.class
548 Note: The compiler compiled src/farewells/Base.java, even though
552 we didn't specify it on the command line. To trace automatic com‐
553 piles, use the -verbose option.
554 Cross-Compilation Example
556 Here we use javac to compile code that will run on a 1.4 VM.
557 % javac -target 1.4 -bootclasspath jdk1.4.2/lib/classes.zip \
559 -extdirs "" OldCode.java
560 The -target 1.4 option ensures that the generated class files will
563 be compatible with 1.4 VMs. By default, javac compiles for JDK 6.
564 The Java Platform JDK's javac would also by default compile against
566 its own bootstrap classes, so we need to tell javac to compile
567 against JDK 1.4 bootstrap classes instead. We do this with -boot‐
568 classpath and -extdirs. Failing to do this might allow compilation
569 against a Java Platform API that would not be present on a 1.4 VM
570 and would fail at runtime.
571
573 o java - the Java Application Launcher
574 o jdb - Java Application Debugger
576 o javah - C Header and Stub File Generator
578 o javap - Class File Disassembler
580 o javadoc - API Documentation Generator
582 o jar - JAR Archive Tool
584 o The Java Extensions Framework @
586 http://java.sun.com/javase/6/docs/technotes/guides/exten‐
587 sions/index.html
588 07 Aug 2006 javac(1)