--- old/src/java.base/share/classes/java/net/Authenticator.java	2020-07-23 17:23:14.407597194 -0700
+++ new/src/java.base/share/classes/java/net/Authenticator.java	2020-07-23 17:23:14.015597194 -0700
@@ -75,6 +75,11 @@
     private final String key = AuthenticatorKeys.computeKey(this);
 
     /**
+     * Constructor for subclasses to call.
+     */
+    public Authenticator() {}
+
+    /**
      * The type of the entity requesting authentication.
      *
      * @since 1.5
--- old/src/java.base/share/classes/java/net/CacheRequest.java	2020-07-23 17:23:15.227597194 -0700
+++ new/src/java.base/share/classes/java/net/CacheRequest.java	2020-07-23 17:23:14.743597194 -0700
@@ -44,6 +44,11 @@
 public abstract class CacheRequest {
 
     /**
+     * Constructor for subclasses to call.
+     */
+    public CacheRequest() {}
+
+    /**
      * Returns an OutputStream to which the response body can be
      * written.
      *
--- old/src/java.base/share/classes/java/net/CacheResponse.java	2020-07-23 17:23:15.991597194 -0700
+++ new/src/java.base/share/classes/java/net/CacheResponse.java	2020-07-23 17:23:15.603597194 -0700
@@ -42,6 +42,11 @@
 public abstract class CacheResponse {
 
     /**
+     * Constructor for subclasses to call.
+     */
+    public CacheResponse() {}
+
+    /**
      * Returns the response headers as a Map.
      *
      * @return An immutable Map from response header field names to
--- old/src/java.base/share/classes/java/net/ContentHandler.java	2020-07-23 17:23:16.667597194 -0700
+++ new/src/java.base/share/classes/java/net/ContentHandler.java	2020-07-23 17:23:16.295597194 -0700
@@ -84,6 +84,11 @@
 public abstract class ContentHandler {
 
     /**
+     * Constructor for subclasses to call.
+     */
+    public ContentHandler() {}
+
+    /**
      * Given a URL connect stream positioned at the beginning of the
      * representation of an object, this method reads that stream and
      * creates an object from it.
--- old/src/java.base/share/classes/java/net/CookieHandler.java	2020-07-23 17:23:17.395597194 -0700
+++ new/src/java.base/share/classes/java/net/CookieHandler.java	2020-07-23 17:23:16.987597194 -0700
@@ -51,6 +51,11 @@
  */
 public abstract class CookieHandler {
     /**
+     * Constructor for subclasses to call.
+     */
+    public CookieHandler() {}
+
+    /**
      * The system-wide cookie handler that will apply cookies to the
      * request headers and manage cookies from the response headers.
      *
--- old/src/java.base/share/classes/java/net/DatagramSocketImpl.java	2020-07-23 17:23:18.083597194 -0700
+++ new/src/java.base/share/classes/java/net/DatagramSocketImpl.java	2020-07-23 17:23:17.703597194 -0700
@@ -58,6 +58,11 @@
 public abstract class DatagramSocketImpl implements SocketOptions {
 
     /**
+     * Constructor for subclasses to call.
+     */
+    public DatagramSocketImpl() {}
+
+    /**
      * The local port number.
      */
     protected int localPort;
--- old/src/java.base/share/classes/java/net/ProxySelector.java	2020-07-23 17:23:18.803597194 -0700
+++ new/src/java.base/share/classes/java/net/ProxySelector.java	2020-07-23 17:23:18.419597194 -0700
@@ -81,6 +81,11 @@
     }
 
     /**
+     * Constructor for subclasses to call.
+     */
+    public ProxySelector() {}
+
+    /**
      * Gets the system-wide proxy selector.
      *
      * @throws  SecurityException
--- old/src/java.base/share/classes/java/net/ResponseCache.java	2020-07-23 17:23:19.527597194 -0700
+++ new/src/java.base/share/classes/java/net/ResponseCache.java	2020-07-23 17:23:19.135597194 -0700
@@ -61,6 +61,11 @@
 public abstract class ResponseCache {
 
     /**
+     * Constructor for subclasses to call.
+     */
+    public ResponseCache() {}
+
+    /**
      * The system wide cache that provides access to a url
      * caching mechanism.
      *
--- old/src/java.base/share/classes/java/net/SecureCacheResponse.java	2020-07-23 17:23:20.267597194 -0700
+++ new/src/java.base/share/classes/java/net/SecureCacheResponse.java	2020-07-23 17:23:19.863597194 -0700
@@ -40,6 +40,11 @@
  */
 public abstract class SecureCacheResponse extends CacheResponse {
     /**
+     * Constructor for subclasses to call.
+     */
+    public SecureCacheResponse() {}
+
+    /**
      * Returns the cipher suite in use on the original connection that
      * retrieved the network resource.
      *
--- old/src/java.base/share/classes/java/net/SocketAddress.java	2020-07-23 17:23:21.003597194 -0700
+++ new/src/java.base/share/classes/java/net/SocketAddress.java	2020-07-23 17:23:20.599597194 -0700
@@ -43,4 +43,8 @@
     @java.io.Serial
     static final long serialVersionUID = 5215720748342549866L;
 
+    /**
+     * Constructor for subclasses to call.
+     */
+    public SocketAddress() {}
 }
--- old/src/java.base/share/classes/java/net/URLDecoder.java	2020-07-23 17:23:21.703597194 -0700
+++ new/src/java.base/share/classes/java/net/URLDecoder.java	2020-07-23 17:23:21.315597194 -0700
@@ -81,6 +81,12 @@
 
 public class URLDecoder {
 
+    /**
+     * Do not call.
+     */
+    @Deprecated(since="16", forRemoval=true)
+    public URLDecoder() {}
+
     // The platform default encoding
     static String dfltEncName = URLEncoder.dfltEncName;
 
--- old/src/java.base/share/classes/java/net/URLStreamHandler.java	2020-07-23 17:23:22.427597194 -0700
+++ new/src/java.base/share/classes/java/net/URLStreamHandler.java	2020-07-23 17:23:22.055597194 -0700
@@ -52,6 +52,11 @@
  */
 public abstract class URLStreamHandler {
     /**
+     * Constructor for subclasses to call.
+     */
+    public URLStreamHandler() {}
+
+    /**
      * Opens a connection to the object referenced by the
      * {@code URL} argument.
      * This method should be overridden by a subclass.