8250213: Address use of default constructors in com.sun.source.util

Reviewed-by: jjg

src/jdk.compiler/share/classes/com/sun/source/util/DocTreePathScanner.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2006, 2014, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2006, 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
@@ -38,6 +38,11 @@ import com.sun.source.doctree.DocTree;
  * @since 1.8
  */
 public class DocTreePathScanner<R, P> extends DocTreeScanner<R, P> {
+    /**
+     * Constructs a {@code DocTreePathScanner}.
+     */
+    public DocTreePathScanner() {}
+
     /**
      * Scans a tree from a position identified by a tree path.
      * @param path the path

src/jdk.compiler/share/classes/com/sun/source/util/DocTreeScanner.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2011, 2019, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2011, 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 +68,10 @@ import com.sun.source.doctree.*;
  * @since 1.8
  */
 public class DocTreeScanner<R,P> implements DocTreeVisitor<R,P> {
+    /**
+     * Constructs a {@code DocTreeScanner}.
+     */
+    public DocTreeScanner() {}
 
     /**
      * Scans a single node.

src/jdk.compiler/share/classes/com/sun/source/util/DocTrees.java

@@ -46,6 +46,11 @@ import com.sun.source.doctree.DocTree;
  * @since 1.8
  */
 public abstract class DocTrees extends Trees {
+    /**
+     * Constructor for subclasses to call.
+     */
+    public DocTrees() {}
+
     /**
      * Returns a DocTrees object for a given CompilationTask.
      * @param task the compilation task for which to get the Trees object

src/jdk.compiler/share/classes/com/sun/source/util/JavacTask.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2005, 2019, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2005, 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 +50,10 @@ import com.sun.tools.javac.util.Context;
  * @since 1.6
  */
 public abstract class JavacTask implements CompilationTask {
+    /**
+     * Constructor for subclasses to call.
+     */
+    public JavacTask() {}
 
     /**
      * Returns the {@code JavacTask} for a {@code ProcessingEnvironment}.

src/jdk.compiler/share/classes/com/sun/source/util/TreePathScanner.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2006, 2016, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2006, 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
@@ -43,6 +43,10 @@ import com.sun.source.tree.*;
  * @since 1.6
  */
 public class TreePathScanner<R, P> extends TreeScanner<R, P> {
+    /**
+     * Constructs a {@code TreePathScanner}.
+     */
+    public TreePathScanner() {}
 
     /**
      * Scans a tree from a position identified by a TreePath.

src/jdk.compiler/share/classes/com/sun/source/util/TreeScanner.java

@@ -75,6 +75,10 @@ import com.sun.source.tree.*;
  * @since 1.6
  */
 public class TreeScanner<R,P> implements TreeVisitor<R,P> {
+    /**
+     * Constructs a {@code TreeScanner}.
+     */
+    public TreeScanner() {}
 
     /**
      * Scans a single node.

src/jdk.compiler/share/classes/com/sun/source/util/Trees.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2005, 2014, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2005, 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
@@ -52,6 +52,11 @@ import com.sun.source.tree.Tree;
  * @author Peter von der Ahé
  */
 public abstract class Trees {
+    /**
+     * Constructor for subclasses to call.
+     */
+    public Trees() {}
+
     /**
      * Returns a Trees object for a given CompilationTask.
      * @param task the compilation task for which to get the Trees object

src/jdk.compiler/share/classes/com/sun/tools/javac/Main.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1999, 2018, 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
@@ -34,6 +34,11 @@ import java.io.PrintWriter;
  * module for details on replacement APIs.
  */
 public class Main {
+    /**
+     * Do not call.
+     */
+    @Deprecated(since="16", forRemoval=true)
+    public Main(){}
 
     /** Main entry point for the launcher.
      *  Note: This method calls System.exit.