"javac -verbose" - Printing Compilation Details

Java Tools Tutorials - Herong's Tutorial Examples

∟"javac -verbose" - Printing Compilation Details

This section provides a tutorial example on how to use the '-verbose' option to print compilation details.

If you want to see what the compiler is doing during the compilation process, you can use the "javac" option "-verbose".

Here is my test of "javac -verbose" command using JDK 17:

herong> javac -verbose Hello.java

[parsing started SimpleFileObject[C:\herong\Hello.java]]
[parsing completed 16ms]

[loading /modules/jdk.jdeps/module-info.class]
[loading /modules/java.management/module-info.class]
[loading /modules/java.transaction.xa/module-info.class]
[loading /modules/jdk.security.auth/module-info.class]
[loading /modules/jdk.internal.le/module-info.class]
[loading /modules/jdk.charsets/module-info.class]
[loading /modules/jdk.editpad/module-info.class]
[loading /modules/java.xml.crypto/module-info.class]
[loading /modules/jdk.internal.vm.ci/module-info.class]
[loading /modules/jdk.internal.vm.compiler.management/module-info.class]
...

[search path for source files: .]
[search path for class files: C:\Progra~1\java\jdk-17.0.1\lib\modules,.]
[loading /modules/java.base/java/lang/Object.class]
[loading /modules/java.base/java/lang/String.class]
[loading /modules/java.base/java/lang/Deprecated.class]
[loading /modules/java.base/java/lang/annotation/Retention.class]
[loading /modules/java.base/java/lang/annotation/RetentionPolicy.class]
[loading /modules/java.base/java/lang/annotation/Target.class]
[loading /modules/java.base/java/lang/annotation/ElementType.class]
[checking Hello]
[loading /modules/java.base/java/io/Serializable.class]
[loading /modules/java.base/java/lang/AutoCloseable.class]
[loading /modules/java.base/java/lang/System.class]
[loading /modules/java.base/java/io/PrintStream.class]
[loading /modules/java.base/java/lang/Appendable.class]
[loading /modules/java.base/java/io/Closeable.class]
[loading /modules/java.base/java/io/FilterOutputStream.class]
[loading /modules/java.base/java/io/OutputStream.class]
[loading /modules/java.base/java/io/Flushable.class]
[loading /modules/java.base/java/lang/Comparable.class]
[loading /modules/java.base/java/lang/CharSequence.class]
[loading /modules/java.base/java/lang/constant/Constable.class]
[loading /modules/java.base/java/lang/constant/ConstantDesc.class]
[wrote Hello.class]
[total 250ms]

The compiler seems to load classes needed to run the compiler first. Then it loads classes that are required for the Hello.java program.

By the way, Oracle are changing the compilation process between JDK versions. Here is my test of "javac -verbose" command using JDK 10:

herong> \Progra~1\java\jdk-10.0.1\bin\javac -verbose Hello.java

parsing started SimpleFileObject[C:\herong\Hello.java]]
parsing completed 31ms]

loading /modules/jdk.management.jfr/module-info.class]
loading /modules/javafx.deploy/module-info.class]
loading /modules/java.xml/module-info.class]
loading /modules/java.desktop/module-info.class]
loading /modules/java.security.sasl/module-info.class]
loading /modules/jdk.management.agent/module-info.class]
loading /modules/jdk.unsupported/module-info.class]
loading /modules/javafx.fxml/module-info.class]
loading /modules/jdk.rmic/module-info.class]
loading /modules/javafx.swing/module-info.class]
...

search path for source files: .]
search path for class files: C:\Progra~1\java\jdk-10.0.1\lib\modules,.]
loading /modules/java.base/java/lang/Object.class]
loading /modules/java.base/java/lang/String.class]
loading /modules/java.base/java/lang/Deprecated.class]
loading /modules/java.base/java/lang/annotation/Retention.class]
loading /modules/java.base/java/lang/annotation/RetentionPolicy.class]
loading /modules/java.base/java/lang/annotation/Target.class]
loading /modules/java.base/java/lang/annotation/ElementType.class]

checking Hello]
loading /modules/java.base/java/io/Serializable.class]
loading /modules/java.base/java/lang/AutoCloseable.class]
loading /modules/java.base/java/lang/System.class]
loading /modules/java.base/java/io/PrintStream.class]
loading /modules/java.base/java/lang/Appendable.class]
loading /modules/java.base/java/io/Closeable.class]
loading /modules/java.base/java/io/FilterOutputStream.class]
loading /modules/java.base/java/io/OutputStream.class]
loading /modules/java.base/java/io/Flushable.class]
loading /modules/java.base/java/lang/Comparable.class]
loading /modules/java.base/java/lang/CharSequence.class]

wrote SimpleFileObject[C:\herong\Hello.class]]
total 343ms]

Here is my test of "javac -verbose" command using JDK 1.8:

herong> \Progra~1\java\jdk1.8.0\bin\javac -verbose Hello.java

[parsing started RegularFileObject[Hello.java]]
[parsing completed 47ms]

[search path for source files: .]
[search path for class files:
   C:\progra~1\java\jdk1.8.0\jre\lib\resources.jar,
   C:\progra~1\java\jdk1.8.0\jre\lib\rt.jar,
   C:\local\jdk\jre\lib\sunrsasign.jar,
   ...

[loading ZipFileIndexFileObject[
   C:\progra~1\java\jdk1.8.0\lib\ct.sym
   (META-INF/sym/rt.jar/java/lang/Object.class)]]
[loading ZipFileIndexFileObject[
   C:\progra~1\java\jdk1.8.0\lib\ct.sym
   (META-INF/sym/rt.jar/java/lang/String.class)]]

[checking Hello]

[loading ZipFileIndexFileObject[...java/lang/Serializable.class)]]
[loading ZipFileIndexFileObject[...java/lang/AutoCloseable.class)]]
[loading ZipFileIndexFileObject[...java/lang/Byte.class)]]
...

[wrote RegularFileObject[Hello.class]]
[total 1924ms]