Javac reads Java class and interface definitions and compiles them into bytecode class files.

When compiling a source file, the compiler often needs information about a type it does not yet recognize. The compiler needs type information for every class or interface used, extended, or implemented in the source file. This includes classes and interfaces not explicitly mentioned in the source file but which provide information through inheritance.

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. The user class path is defined by setting the CLASSPATH environment variable or by using the -classpath command line option. 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.

We will use the -bootclasspath, -target, and -extdirs options when we cross-compile code for J2ME/CLDC.

ref: <JAVA_HOME>/docs/tooldocs/windows/javac.html

java

javaw

On the PC, or other interpreted Java platforms, Java launches a program by starting a Java runtime environment, loading a specified class, and invoking that class's main method. The javaw command is identical to java, except that with javaw there is no associated console window. Use javaw when you don't want a command prompt window to appear. The javaw launcher will, however, display a dialog box with error information if a launch fails for some reason.

If a Java program fails to load and start, it can be very frustrating trying to determine the reasons why, since the default error messages are terse and cryptic. The -verbose option provides a lot of information, and will generally be very helpful in debugging program start and load problems.

Our native-execution embedded Java programs will not be started in this way, because the Java runtime environment is in silicon and automatically starts upon power-up. Rather, you specifiy your desired boot class to Jembuilder, and it's main() method executes at any power-up or reset event.