diff -r 1fdb98a17101 -r d95b224e9f17 src/share/vm/runtime/java.cpp
--- a/src/share/vm/runtime/java.cpp	Sat Jul 19 17:38:22 2008 -0400
+++ b/src/share/vm/runtime/java.cpp	Mon Jul 28 14:07:44 2008 -0400
@@ -563,32 +563,104 @@
   vm_shutdown();
 }
 
-jdk_version_info JDK_Version::_version_info = {0};
-bool JDK_Version::_pre_jdk16_version = false;
-int  JDK_Version::_jdk_version = 0;
+JDK_Version JDK_Version::_current;
 
 void JDK_Version::initialize() {
+  jdk_version_info info;
+  assert(!_current.is_valid(), "Don't initialize twice");
+
   void *lib_handle = os::native_java_library();
-  jdk_version_info_fn_t func =
-    CAST_TO_FN_PTR(jdk_version_info_fn_t, hpi::dll_lookup(lib_handle, "JDK_GetVersionInfo0"));
+  jdk_version_info_fn_t func = CAST_TO_FN_PTR(jdk_version_info_fn_t,
+     os::dll_lookup(lib_handle, "JDK_GetVersionInfo0"));
 
   if (func == NULL) {
     // JDK older than 1.6
-    _pre_jdk16_version = true;
-    return;
+    _current._partially_initialized = true;
+  } else {
+    (*func)(&info, sizeof(info));
+
+    int major = JDK_VERSION_MAJOR(info.jdk_version);
+    int minor = JDK_VERSION_MINOR(info.jdk_version);
+    int micro = JDK_VERSION_MICRO(info.jdk_version);
+    int build = JDK_VERSION_BUILD(info.jdk_version);
+    if (major == 1 && minor > 4) {
+      // We represent "1.5.0" as "5.0", but 1.4.2 as itself.
+      major = minor;
+      minor = micro;
+      micro = 0;
+    }
+    _current = JDK_Version(major, minor, micro, info.update_version,
+                           info.special_update_version, build,
+                           info.thread_park_blocker == 1);
   }
+}
 
-  if (func != NULL) {
-    (*func)(&_version_info, sizeof(_version_info));
+void JDK_Version::fully_initialize(
+    uint8_t major, uint8_t minor, uint8_t micro, uint8_t update) {
+  // This is only called when current is less than 1.6 and we've gotten
+  // far enough in the initialization to determine the exact version.
+  assert(major < 6, "not needed for JDK version >= 6");
+  assert(is_partially_initialized(), "must not initialize");
+  if (major < 5) {
+    // JDK verison sequence: 1.2.x, 1.3.x, 1.4.x, 5.0.x, 6.0.x, etc.
+    micro = minor;
+    minor = major;
+    major = 1;
   }
-  if (jdk_major_version() == 1) {
-    _jdk_version = jdk_minor_version();
-  } else {
-    // If the release version string is changed to n.x.x (e.g. 7.0.0) in a future release
-    _jdk_version = jdk_major_version();
-  }
+  _current = JDK_Version(major, minor, micro, update);
 }
 
 void JDK_Version_init() {
   JDK_Version::initialize();
 }
+
+static int64_t encode_jdk_version(const JDK_Version& v) {
+  return
+    ((int64_t)v.major_version()          << (BitsPerByte * 5)) |
+    ((int64_t)v.minor_version()          << (BitsPerByte * 4)) |
+    ((int64_t)v.micro_version()          << (BitsPerByte * 3)) |
+    ((int64_t)v.update_version()         << (BitsPerByte * 2)) |
+    ((int64_t)v.special_update_version() << (BitsPerByte * 1)) |
+    ((int64_t)v.build_number()           << (BitsPerByte * 0));
+}
+
+int JDK_Version::compare(const JDK_Version& other) const {
+  assert(is_valid() && other.is_valid(), "Invalid version (uninitialized?)");
+  if (!is_partially_initialized() && other.is_partially_initialized()) {
+    return -(other.compare(*this)); // flip the comparators
+  }
+  assert(!other.is_partially_initialized(), "Not initialized yet");
+  if (is_partially_initialized()) {
+    assert(other.major_version() >= 6,
+           "Invalid JDK version comparison during initialization");
+    return -1;
+  } else {
+    uint64_t e = encode_jdk_version(*this);
+    uint64_t o = encode_jdk_version(other);
+    return (e > o) ? 1 : ((e == o) ? 0 : -1);
+  }
+}
+
+void JDK_Version::to_string(char* buffer, size_t buflen) const {
+  size_t index = 0;
+  if (!is_valid()) {
+    jio_snprintf(buffer, buflen, "%s", "(uninitialized)");
+  } else if (is_partially_initialized()) {
+    jio_snprintf(buffer, buflen, "%s", "(uninitialized) pre-1.6.0");
+  } else {
+    index += jio_snprintf(
+        &buffer[index], buflen - index, "%d.%d", _major, _minor);
+    if (_micro > 0) {
+      index += jio_snprintf(&buffer[index], buflen - index, ".%d", _micro);
+    }
+    if (_update > 0) {
+      index += jio_snprintf(&buffer[index], buflen - index, "_%02d", _update);
+    }
+    if (_special > 0) {
+      index += jio_snprintf(&buffer[index], buflen - index, "%c", _special);
+    }
+    if (_build > 0) {
+      index += jio_snprintf(&buffer[index], buflen - index, "-b%02d", _build);
+    }
+  }
+}