Lets consider following sample:<\/p>\n
[code lang=”java”]
\npublic class Test {
\nstatic class FooException extends Exception {
\n}
\nstatic class BarException extends Exception {
\n}<\/p>\n
static System.out.println(”throw runtime”); static String test(int x) throws FooException, BarException { public static void call(int x) { public static void main(String[] args ){ Compile and run: And end result is this: What the heck that means? Well it means magic<\/strong>. Basically it allows catching arbitrary exception and then rethrowing it with approriate typing. In normal application code there ain’t naturally any use for such, but when you consider that there could be generic framework piece, which allows passing in typing of throws clause, then it’s possible to sensible typed exception throwing from generic code.<\/p>\n Example of such framework …<\/p>\n \/\/ And usage is something like this Lets consider following sample: [code lang=”java”] public class Test { static class FooException extends Exception { } static class BarException extends Exception { } static Z rethrow(Throwable e, Class a, Class b) throws T, E { if (a.isAssignableFrom(e.getClass())) { System.out.println(”throw ” + a.getName()); throw (T)e; } else if (b.isAssignableFrom(e.getClass())) { System.out.println(”throw ” + b.getName()); throw…<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[7],"tags":[],"class_list":["post-377","post","type-post","status-publish","format-standard","hentry","category-java"],"_links":{"self":[{"href":"https:\/\/kari.world.ikari.fi\/index.php?rest_route=\/wp\/v2\/posts\/377","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/kari.world.ikari.fi\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/kari.world.ikari.fi\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/kari.world.ikari.fi\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/kari.world.ikari.fi\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=377"}],"version-history":[{"count":0,"href":"https:\/\/kari.world.ikari.fi\/index.php?rest_route=\/wp\/v2\/posts\/377\/revisions"}],"wp:attachment":[{"href":"https:\/\/kari.world.ikari.fi\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=377"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/kari.world.ikari.fi\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=377"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/kari.world.ikari.fi\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=377"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}
\n throws T, E
\n{
\n if (a.isAssignableFrom(e.getClass())) {
\n System.out.println(”throw ” + a.getName());
\n throw (T)e;
\n } else if (b.isAssignableFrom(e.getClass())) {
\n System.out.println(”throw ” + b.getName());
\n throw (E)e;
\n }<\/p>\n
\n throw new RuntimeException(e);
\n}<\/p>\n
\n try {
\n if (x == 0) {
\n throw new FooException();
\n }
\n if (x == 1) {
\n throw new BarException();
\n }
\n if (x == 2) {
\n throw new Exception(”goatch”);
\n }
\n return ”DONE-” + x;
\n } catch (Throwable e) {
\n return rethrow(e, BarException.class, FooException.class);
\n }
\n}<\/p>\n
\n try {
\n String t = test(x);
\n System.out.println(”RESULT=” + t);
\n } catch (FooException e) {
\n System.out.println(”foo”);
\n e.printStackTrace();
\n } catch (BarException e) {
\n System.out.println(”bar”);
\n e.printStackTrace();
\n } catch (Exception e) {
\n System.out.println(”OTHER”);
\n e.printStackTrace();
\n }
\n}<\/p>\n
\n call(0);
\n call(1);
\n call(2);
\n call(3);
\n}
\n}
\n[\/code]<\/p>\n
\n[code]
\njavac Test.java && java Test
\n[\/code]<\/p>\n
\n[code]
\nthrow Test$FooException
\nfoo
\nTest$FooException
\n at Test.test(Test.java:37)
\n at Test.call(Test.java:54)
\n at Test.main(Test.java:68)
\nthrow Test$BarException
\nbar
\nTest$BarException
\n at Test.test(Test.java:40)
\n at Test.call(Test.java:54)
\n at Test.main(Test.java:69)
\nthrow runtime
\nOTHER
\njava.lang.RuntimeException: java.lang.Exception: goatch
\n at Test.rethrow(Test.java:19)
\n at Test.test(Test.java:47)
\n at Test.call(Test.java:54)
\n at Test.main(Test.java:70)
\nCaused by: java.lang.Exception: goatch
\n at Test.test(Test.java:43)
\n … 2 more
\nRESULT=DONE-3
\n[\/code]<\/p>\n
\n[code lang=”java”]
\npublic abstract class TX {
\n public
\n … private framework logic
\n }
\n public abstract Object run() throws Exception;
\n}<\/p>\n
\ntry {
\n new TX() {
\n public Object run() throws Exception() {
\n throws new IOExcecption();
\n }
\n }.start(IOExcecption.class);
\n} catch (KnownException e) {
\n \/\/ easy; framework throws this always
\n} catch (IOException e) {
\n \/\/ magic; typed catch using generics
\n} catch (RuntimeException e) {
\n \/\/ without magic; this would be only only
\n \/\/ alternative to KnownException
\n}
\n[\/code]<\/p>\n","protected":false},"excerpt":{"rendered":"