JDK-6586569 : Class.cast exception detail construction should be refactored
  • Type: Bug
  • Component: core-libs
  • Sub-Component: java.lang:reflect
  • Affected Version: 7
  • Priority: P3
  • Status: Closed
  • Resolution: Fixed
  • OS: generic
  • CPU: generic
  • Submitted: 2007-07-28
  • Updated: 2012-09-28
  • Resolved: 2011-05-18
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JDK 7
7 b18Fixed
Related Reports
Relates :  
JDK-6587525 - ClassCastException needs "origin" and "target" attributes
Relates :  
JDK-6456938 - (reflect) Class.cast(Object) throws CCE without detail message
Description
Experience has shown that refactoring complex exception detail message
constructions to a separate method tends to improve performance
with JDK's runtime compilers.

--- /u/martin/ws/dolphin/src/share/classes/java/lang/Class.java	2007-06-28 14:57:58.260063000 -0700
+++ /u/martin/ws/checked/src/share/classes/java/lang/Class.java	2007-07-26 16:55:10.570075000 -0700
@@ -3005,11 +3005,14 @@
      */
     public T cast(Object obj) {
 	if (obj != null && !isInstance(obj))
-	    throw new ClassCastException("Cannot cast " + obj.getClass().getName() 
-					 + " to " + getName());
+	    throw new ClassCastException(cannotCastMsg(obj));
 	return (T) obj;
     }
 
+    private String cannotCastMsg(Object obj) {
+	return "Cannot cast " + obj.getClass().getName() + " to " + getName();
+    }
+
     /**
      * Casts this {@code Class} object to represent a subclass of the class
      * represented by the specified class object.  Checks that that the cast
Comments
EVALUATION Indeed. The following microbenchmark shows 30% performance gains on sparc, 15% on x86, with the Class.cast "job": import java.util.*; public class TypeCheckMicroBenchmark { abstract static class Job { private final String name; Job(String name) { this.name = name; } String name() { return name; } abstract void work() throws Throwable; } private static void collectAllGarbage() { final java.util.concurrent.CountDownLatch drained = new java.util.concurrent.CountDownLatch(1); try { System.gc(); // enqueue finalizable objects new Object() { protected void finalize() { drained.countDown(); }}; System.gc(); // enqueue detector drained.await(); // wait for finalizer queue to drain System.gc(); // cleanup finalized objects } catch (InterruptedException e) { throw new Error(e); } } /** * Runs each job for long enough that all the runtime compilers * have had plenty of time to warm up, i.e. get around to * compiling everything worth compiling. * Returns array of average times per job per run. */ private static long[] time0(Job ... jobs) throws Throwable { final long warmupNanos = 10L * 1000L * 1000L * 1000L; long[] nanoss = new long[jobs.length]; for (int i = 0; i < jobs.length; i++) { collectAllGarbage(); long t0 = System.nanoTime(); long t; int j = 0; do { jobs[i].work(); j++; } while ((t = System.nanoTime() - t0) < warmupNanos); nanoss[i] = t/j; } return nanoss; } private static void time(Job ... jobs) throws Throwable { long[] warmup = time0(jobs); // Warm up run long[] nanoss = time0(jobs); // Real timing run long[] milliss = new long[jobs.length]; double[] ratios = new double[jobs.length]; final String nameHeader = "Method"; final String millisHeader = "Millis"; final String ratioHeader = "Ratio"; int nameWidth = nameHeader.length(); int millisWidth = millisHeader.length(); int ratioWidth = ratioHeader.length(); for (int i = 0; i < jobs.length; i++) { nameWidth = Math.max(nameWidth, jobs[i].name().length()); milliss[i] = nanoss[i]/(1000L * 1000L); millisWidth = Math.max(millisWidth, String.format("%d", milliss[i]).length()); ratios[i] = (double) nanoss[i] / (double) nanoss[0]; ratioWidth = Math.max(ratioWidth, String.format("%.3f", ratios[i]).length()); } String format = String.format("%%-%ds %%%dd %%%d.3f%%n", nameWidth, millisWidth, ratioWidth); String headerFormat = String.format("%%-%ds %%%ds %%%ds%%n", nameWidth, millisWidth, ratioWidth); System.out.printf(headerFormat, "Method", "Millis", "Ratio"); // Print out absolute and relative times, calibrated against first job for (int i = 0; i < jobs.length; i++) System.out.printf(format, jobs[i].name(), milliss[i], ratios[i]); } private static String keywordValue(String[] args, String keyword) { for (String arg : args) if (arg.startsWith(keyword)) return arg.substring(keyword.length() + 1); return null; } private static int intArg(String[] args, String keyword, int defaultValue) { String val = keywordValue(args, keyword); return val == null ? defaultValue : Integer.parseInt(val); } private static java.util.regex.Pattern patternArg(String[] args, String keyword) { String val = keywordValue(args, keyword); return val == null ? null : java.util.regex.Pattern.compile(val); } private static Job[] filter(java.util.regex.Pattern filter, Job[] jobs) { if (filter == null) return jobs; Job[] newJobs = new Job[jobs.length]; int n = 0; for (Job job : jobs) if (filter.matcher(job.name()).find()) newJobs[n++] = job; // Arrays.copyOf not available in JDK 5 Job[] ret = new Job[n]; System.arraycopy(newJobs, 0, ret, 0, n); return ret; } /** * Usage: [iterations=N] [size=N] [filter=REGEXP] */ public static void main(String[] args) throws Throwable { final int iterations = intArg(args, "iterations", 30000); final int size = intArg(args, "size", 1000); final java.util.regex.Pattern filter = patternArg(args, "filter"); final List<Integer> list = new ArrayList<Integer>(); final Random rnd = new Random(); for (int i = 0; i < size; i++) list.add(rnd.nextInt()); final Class klazz = Integer.class; final Job[] jobs = { new Job("toArray(T[])") { void work() { Object[] a = new Integer[0]; for (int i = 0; i < iterations; i++) { try { list.toArray(a); } catch (ArrayStoreException ase) { throw new ClassCastException(); }}}}, new Job("isInstance") { void work() { for (int i = 0; i < iterations; i++) { for (Object x : list.toArray()) if (! (x != null && klazz.isInstance(x))) throw new ClassCastException(); }}}, new Job("Class.cast") { void work() { for (int i = 0; i < iterations; i++) { for (Object x : list.toArray()) klazz.cast(x); }}}, new Job("write into array") { void work() { Object[] a = new Integer[1]; for (int i = 0; i < iterations; i++) { for (Object x : list.toArray()) { try { a[0] = x; } catch (ArrayStoreException _) { throw new ClassCastException(); }}}}}, new Job("write into dynamic array") { void work() { for (int i = 0; i < iterations; i++) { for (Object x : list.toArray()) { Object[] a = (Object[]) java.lang.reflect.Array.newInstance(klazz, 1); try { a[0] = x; } catch (ArrayStoreException _) { throw new ClassCastException(); }}}}} }; time(filter(filter, jobs)); } }
28-07-2007