The Former Weblog of Peter Ahé

So while this is good style:

/** * ... * @throws java.lang.RuntimeException if an unrecoverable error * occurred in a user supplied component. The cause will be the * error in user code. */

This is not:

void run() throws RuntimeException;

So how can I reliably find all unchecked exceptions? Very easily if I use an annotation processor. I used this annotation processor:

@SupportedAnnotationTypes("*") @SupportedOptions("summary") public class FindRuntimeException extends AbstractProcessor { // For summary of unchecked exceptions used in throws clauses final Set<TypeMirror> uncheckedExceptions = new LinkedHashSet<TypeMirror>(); public boolean process(Set<? extends TypeElement> annotations, RoundEnvironment roundEnvironment) { // Get various utility classes final Elements elements = processingEnv.getElementUtils(); final Types types = processingEnv.getTypeUtils(); final Messager log = processingEnv.getMessager(); // Get the types (type mirrors) of RuntimeException and Error final TypeMirror runtimeException = elements.getTypeElement("java.lang.RuntimeException").asType(); final TypeMirror error = elements.getTypeElement("java.lang.Error").asType(); // Scanner for traversing the structure of a class, interface, etc. ElementScanner6<Void,Void> scan = new ElementScanner6<Void,Void>() { @Override public Void visitExecutable(ExecutableElement e, Void p) { // Executable means method or constructor, this method is called for // every method or constructor. So we just have to look at the throws // declaration... for (TypeMirror t :e.getThrownTypes()) // ...and see if any of the thrown types are subtypes of // RuntimeException or Error. if (types.isSubtype(t, runtimeException) || types.isSubtype(t, error)) { uncheckedExceptions.add(t); // print a warning so you can use your favorite editor to jump // to the problematic method log.printMessage(WARNING, "Throwing unchecked exception " + t, e); } return null; } }; // examine all the classes provided on the command line for (TypeElement e : roundEnvironment.getSpecifiedTypeElements()) scan.scan(e); // print a summary of found unchecked exceptions if (roundEnvironment.processingOver() && processingEnv.getOptions().containsKey("summary")) { System.out.println("Summary of unchecked exceptions found in throws clauses:"); for (TypeMirror t : uncheckedExceptions) System.out.println("\t" + t); } return true; } }

UPDATE: I have updated the code with comments and colors (using htmlize.el by Hrvoje Niksic)

Then I compiled the annotation processor:

javac -classpath /usr/java/jdk1.6.0/lib/tools.jar FindRuntimeException.java

You need a fairly recent Mustang snapshot to compile this. Also, from b74 (Thanks Kelly!), you won't have to put tools.jar on the classpath anymore. Then run the annotation processor:

javac -Asummary -proc:only -processor FindRuntimeException src/share/classes/javax/tools/*.java

Enjoy...