src/java.base/windows/classes/java/io/WinNTFileSystem.java

@@ -41,11 +41,12 @@
 class WinNTFileSystem extends FileSystem {
 
     private final char slash;
     private final char altSlash;
     private final char semicolon;
-    private final String userDir;
+    private String userDir;
+    private volatile boolean isUserDirNormal;
 
     public WinNTFileSystem() {
         Properties props = GetPropertyAction.privilegedGetProperties();
         slash = props.getProperty("file.separator").charAt(0);
         semicolon = props.getProperty("path.separator").charAt(0);

@@ -351,11 +352,21 @@
            we must look this up every time */
         SecurityManager sm = System.getSecurityManager();
         if (sm != null) {
             sm.checkPropertyAccess("user.dir");
         }
-        return normalize(userDir);
+        boolean normalize = !isUserDirNormal;
+        if (normalize) {
+            synchronized(userDir) {
+                normalize = !isUserDirNormal;
+                if (normalize) {
+                    userDir = normalize(userDir);
+                    isUserDirNormal = true;
+                }
+            }
+        }
+        return userDir;
     }
 
     private String getDrive(String path) {
         int pl = prefixLength(path);
         return (pl == 3) ? path.substring(0, 2) : null;