1 files changed, 47 insertions, 21 deletions

diff --git a/src/library/scala/util/Properties.scala b/src/library/scala/util/Properties.scala
index 1bdf50bac2..8722294dde 100644
--- a/src/library/scala/util/Properties.scala
+++ b/src/library/scala/util/Properties.scala
@@ -168,33 +168,59 @@ private[scala] trait PropertiesTrait {
 
   /** Compares the given specification version to the specification version of the platform.
    *
-   * @param version a specification version number (legacy forms acceptable)
-   * @return `true` iff the specification version of the current runtime
-   * is equal to or higher than the version denoted by the given string.
-   * @throws NumberFormatException if the given string is not a version string
+   *  @param version a specification version number (legacy forms acceptable)
+   *  @return `true` if the specification version of the current runtime
+   *    is equal to or higher than the version denoted by the given string.
+   *  @throws NumberFormatException if the given string is not a version string
    *
-   * @example {{{
-   * // In this example, the runtime's Java specification is assumed to be at version 8.
-   * isJavaAtLeast("1.6")            // true
-   * isJavaAtLeast("1.8")            // true
-   * isJavaAtLeast("8")              // true
-   * isJavaAtLeast("9")              // false
-   * isJavaAtLeast("1.9")            // throws
-   * }}}
+   *  @example {{{
+   *  // In this example, the runtime's Java specification is assumed to be at version 8.
+   *  isJavaAtLeast("1.8")            // true
+   *  isJavaAtLeast("8")              // true
+   *  isJavaAtLeast("9")              // false
+   *  isJavaAtLeast("9.1")            // false
+   *  isJavaAtLeast("1.9")            // throws
+   *  }}}
    */
   def isJavaAtLeast(version: String): Boolean = {
-    def versionOf(s: String): Int = s.indexOf('.') match {
-      case 1 if s.charAt(0) == '1' =>
-        val v = s.substring(2).toInt
-        if (v < 9) v else -1
-      case -1 => s.toInt
-      case _  => -1
+    def versionOf(s: String, depth: Int): (Int, String) =
+      s.indexOf('.') match {
+        case 0 =>
+          (-2, s.substring(1))
+        case 1 if depth == 0 && s.charAt(0) == '1' =>
+          val r0 = s.substring(2)
+          val (v, r) = versionOf(r0, 1)
+          val n = if (v > 8 || r0.isEmpty) -2 else v   // accept 1.8, not 1.9 or 1.
+          (n, r)
+        case -1 =>
+          val n = if (!s.isEmpty) s.toInt else if (depth == 0) -2 else 0
+          (n, "")
+        case i  =>
+          val r = s.substring(i + 1)
+          val n = if (depth < 2 && r.isEmpty) -2 else s.substring(0, i).toInt
+          (n, r)
+      }
+    def compareVersions(s: String, v: String, depth: Int): Int = {
+      if (depth >= 3) 0
+      else {
+        val (sn, srest) = versionOf(s, depth)
+        val (vn, vrest) = versionOf(v, depth)
+        if (vn < 0) -2
+        else if (sn < vn) -1
+        else if (sn > vn) 1
+        else compareVersions(srest, vrest, depth + 1)
+      }
+    }
+    compareVersions(javaSpecVersion, version, 0) match {
+      case -2 => throw new NumberFormatException(s"Not a version: $version")
+      case i  => i >= 0
     }
-    val v = versionOf(version)
-    if (v < 0) throw new NumberFormatException(s"Not a version: $version")
-    versionOf(javaSpecVersion) >= v
   }
 
+  /** Tests whether the major version of the platform specification is at least the given value.
+   *
+   *  @param version a major version number
+   */
   def isJavaAtLeast(version: Int): Boolean = isJavaAtLeast(version.toString)
 
   // provide a main method so version info can be obtained by running this