Copyright (c) 2004, 2019 IBM Corporation and others.
This program and the accompanying materials
are made available under the terms of the Eclipse Public License 2.0
which accompanies this distribution, and is available at
https://www.eclipse.org/legal/epl-2.0/
SPDX-License-Identifier: EPL-2.0
Contributors:
    IBM Corporation - initial API and implementation
/*******************************************************************************
 * Copyright (c) 2004, 2019 IBM Corporation and others.
 *
 * This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License 2.0
 * which accompanies this distribution, and is available at
 * https://www.eclipse.org/legal/epl-2.0/
 *
 * SPDX-License-Identifier: EPL-2.0
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.jdt.core.dom;

Abstract base class for all AST nodes that represent comments. There are exactly three kinds of comment: line comments (LineComment), block comments (BlockComment), and doc comments (Javadoc). 
Comment:
    LineComment
    BlockComment
    Javadoc

Since:
3.0/**
 * Abstract base class for all AST nodes that represent comments.
 * There are exactly three kinds of comment:
 * line comments ({@link LineComment}),
 * block comments ({@link BlockComment}), and
 * doc comments ({@link Javadoc}).
 * <pre>
 * Comment:
 *     LineComment
 *     BlockComment
 *     Javadoc
 * </pre>
 *
 * @since 3.0
 */
public abstract class Comment extends ASTNode {

	
Alternate root node, or null if none.
Initially null.
/**
	 * Alternate root node, or <code>null</code> if none.
	 * Initially <code>null</code>.
	 */
	private ASTNode alternateRoot = null;

	
Creates a new AST node for a comment owned by the given AST.

N.B. This constructor is package-private.

Params:
ast – the AST that is to own this node/**
	 * Creates a new AST node for a comment owned by the given AST.
	 * <p>
	 * N.B. This constructor is package-private.
	 * </p>
	 *
	 * @param ast the AST that is to own this node
	 */
	Comment(AST ast) {
		super(ast);
	}

	
Returns whether this comment is a block comment
(BlockComment).
Returns:
true if this is a block comment, and
   false otherwise/**
	 * Returns whether this comment is a block comment
	 * (<code>BlockComment</code>).
	 *
	 * @return <code>true</code> if this is a block comment, and
	 *    <code>false</code> otherwise
	 */
	public final boolean isBlockComment() {
		return (this instanceof BlockComment);
	}

	
Returns whether this comment is a line comment
(LineComment).
Returns:
true if this is a line comment, and
   false otherwise/**
	 * Returns whether this comment is a line comment
	 * (<code>LineComment</code>).
	 *
	 * @return <code>true</code> if this is a line comment, and
	 *    <code>false</code> otherwise
	 */
	public final boolean isLineComment() {
		return (this instanceof LineComment);
	}

	
Returns whether this comment is a doc comment
(Javadoc).
Returns:
true if this is a doc comment, and
   false otherwise/**
	 * Returns whether this comment is a doc comment
	 * (<code>Javadoc</code>).
	 *
	 * @return <code>true</code> if this is a doc comment, and
	 *    <code>false</code> otherwise
	 */
	public final boolean isDocComment() {
		return (this instanceof Javadoc);
	}

	
Returns the root AST node that this comment occurs
within, or null if none (or not recorded).
 Typically, the comment nodes created while parsing a compilation unit are not considered descendents of the normal AST root, namely an CompilationUnit. Instead, these comment nodes exist outside the normal AST and each is a root in its own right. This optional property provides a well-known way to navigate from the comment to the compilation unit in such cases. Note that the alternate root property is not one of the comment node's children. It is simply a reference to a node. 
See Also:
setAlternateRoot(ASTNode)
Returns:
the alternate root node, or null
if none/**
	 * Returns the root AST node that this comment occurs
	 * within, or <code>null</code> if none (or not recorded).
	 * <p>
	 * Typically, the comment nodes created while parsing a compilation
	 * unit are not considered descendents of the normal AST
	 * root, namely an {@link CompilationUnit}. Instead, these
	 * comment nodes exist outside the normal AST and each is
	 * a root in its own right. This optional property provides
	 * a well-known way to navigate from the comment to the
	 * compilation unit in such cases. Note that the alternate root
	 * property is not one of the comment node's children. It is simply a
	 * reference to a node.
	 * </p>
	 *
	 * @return the alternate root node, or <code>null</code>
	 * if none
	 * @see #setAlternateRoot(ASTNode)
	 */
	public final ASTNode getAlternateRoot() {
		return this.alternateRoot;
	}

	
Returns the root AST node that this comment occurs
within, or null if none (or not recorded).
Params:
root – the alternate root node, or null
if none
See Also:
getAlternateRoot()/**
	 * Returns the root AST node that this comment occurs
	 * within, or <code>null</code> if none (or not recorded).
	 *
	 * @param root the alternate root node, or <code>null</code>
	 * if none
	 * @see #getAlternateRoot()
	 */
	public final void setAlternateRoot(ASTNode root) {
		// alternate root is *not* considered a structural property
		// but we protect them nevertheless
		checkModifiable();
		this.alternateRoot = root;
	}

	@Override
	int memSize() {
		return BASE_NODE_SIZE + 1 * 4;
	}
}