8250856: Address reliance on default constructors in the AWT APIs

Reviewed-by: prr

src/java.desktop/share/classes/java/awt/event/ComponentAdapter.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1996, 2013, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1996, 2020, 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
@@ -50,6 +50,12 @@ package java.awt.event;
  * @since 1.1
  */
 public abstract class ComponentAdapter implements ComponentListener {
+
+    /**
+     * Constructs a {@code ComponentAdapter}.
+     */
+    protected ComponentAdapter() {}
+
     /**
      * Invoked when the component's size changes.
      */

src/java.desktop/share/classes/java/awt/event/ContainerAdapter.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1996, 2013, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1996, 2020, 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
@@ -50,6 +50,12 @@ package java.awt.event;
  * @since 1.1
  */
 public abstract class ContainerAdapter implements ContainerListener {
+
+    /**
+     * Constructs a {@code ContainerAdapter}.
+     */
+    protected ContainerAdapter() {}
+
     /**
      * Invoked when a component has been added to the container.
      */

src/java.desktop/share/classes/java/awt/event/FocusAdapter.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1996, 2013, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1996, 2020, 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
@@ -50,6 +50,12 @@ package java.awt.event;
  * @since 1.1
  */
 public abstract class FocusAdapter implements FocusListener {
+
+    /**
+     * Constructs a {@code FocusAdapter}.
+     */
+    protected FocusAdapter() {}
+
     /**
      * Invoked when a component gains the keyboard focus.
      */

src/java.desktop/share/classes/java/awt/event/HierarchyBoundsAdapter.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1999, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1999, 2020, 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
@@ -49,6 +49,11 @@ package java.awt.event;
  */
 public abstract class HierarchyBoundsAdapter implements HierarchyBoundsListener
 {
+    /**
+     * Constructs a {@code HierarchyBoundsAdapter}.
+     */
+    protected HierarchyBoundsAdapter() {}
+
     /**
      * Called when an ancestor of the source is moved.
      */

src/java.desktop/share/classes/java/awt/event/KeyAdapter.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1996, 2013, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1996, 2020, 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
@@ -51,6 +51,12 @@ package java.awt.event;
  * @since 1.1
  */
 public abstract class KeyAdapter implements KeyListener {
+
+    /**
+     * Constructs a {@code KeyAdapter}.
+     */
+    protected KeyAdapter() {}
+
     /**
      * Invoked when a key has been typed.
      * This event occurs when a key press is followed by a key release.

src/java.desktop/share/classes/java/awt/event/MouseAdapter.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1996, 2013, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1996, 2020, 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
@@ -68,6 +68,12 @@ package java.awt.event;
  * @since 1.1
  */
 public abstract class MouseAdapter implements MouseListener, MouseWheelListener, MouseMotionListener {
+
+    /**
+     * Constructs a {@code MouseAdapter}.
+     */
+    protected MouseAdapter() {}
+
     /**
      * {@inheritDoc}
      */

src/java.desktop/share/classes/java/awt/event/MouseMotionAdapter.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1996, 2013, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1996, 2020, 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
@@ -54,6 +54,12 @@ package java.awt.event;
  * @since 1.1
  */
 public abstract class MouseMotionAdapter implements MouseMotionListener {
+
+    /**
+     * Constructs a {@code MouseMotionAdapter}.
+     */
+    protected MouseMotionAdapter() {}
+
     /**
      * Invoked when a mouse button is pressed on a component and then
      * dragged.  Mouse drag events will continue to be delivered to

src/java.desktop/share/classes/java/awt/event/WindowAdapter.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1996, 2013, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1996, 2020, 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
@@ -55,6 +55,11 @@ package java.awt.event;
 public abstract class WindowAdapter
     implements WindowListener, WindowStateListener, WindowFocusListener
 {
+    /**
+     * Constructs a {@code WindowAdapter}.
+     */
+    protected WindowAdapter() {}
+
     /**
      * Invoked when a window has been opened.
      */