src/java.base/share/classes/java/lang/NullPointerException.java

rev 54075 : 8218627: Add detailed message to NullPointerException describing what is null.

@@ -1,7 +1,7 @@
 /*
- * Copyright (c) 1994, 2011, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1994, 2019, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
  * under the terms of the GNU General Public License version 2 only, as
  * published by the Free Software Foundation.  Oracle designates this

@@ -51,15 +51,17 @@
  */
 public
 class NullPointerException extends RuntimeException {
     private static final long serialVersionUID = 5162710183389028792L;
 
+    private static final String MESSAGE_PLACEHOLDER = new String();
+
     /**
      * Constructs a {@code NullPointerException} with no detail message.
      */
     public NullPointerException() {
-        super();
+        super(MESSAGE_PLACEHOLDER);
     }
 
     /**
      * Constructs a {@code NullPointerException} with the specified
      * detail message.

@@ -67,6 +69,33 @@
      * @param   s   the detail message.
      */
     public NullPointerException(String s) {
         super(s);
     }
+
+    /**
+     * Returns the detail message string of this throwable.
+     *
+     * @return  the detail message string of this {@code Throwable} instance
+     *          (which may be {@code null}).
+     */
+    public String getMessage() {
+        String message = super.getMessage();
+        if (message == MESSAGE_PLACEHOLDER) {
+            message = getExtendedNPEMessage();
+            setMessage(message);
+        }
+        return message;
+    }
+
+    // Install the extendedMessage in Throwable.defaultMessage before
+    // serializing.
+    private Object writeReplace() {
+        getMessage();
+        return this;
+    }
+
+    // Get an extended exception message. This returns a string describing
+    // the location and cause of the exception. It returns null for
+    // exceptions where this is not applicable.
+    private native String getExtendedNPEMessage();
 }