com.sun.tools.xjc.reader.gbind.Sequence Maven / Gradle / Ivy
/*
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
*
* Copyright (c) 1997-2017 Oracle and/or its affiliates. All rights reserved.
*
* The contents of this file are subject to the terms of either the GNU
* General Public License Version 2 only ("GPL") or the Common Development
* and Distribution License("CDDL") (collectively, the "License"). You
* may not use this file except in compliance with the License. You can
* obtain a copy of the License at
* https://oss.oracle.com/licenses/CDDL+GPL-1.1
* or LICENSE.txt. See the License for the specific
* language governing permissions and limitations under the License.
*
* When distributing the software, include this License Header Notice in each
* file and include the License file at LICENSE.txt.
*
* GPL Classpath Exception:
* Oracle designates this particular file as subject to the "Classpath"
* exception as provided by Oracle in the GPL Version 2 section of the License
* file that accompanied this code.
*
* Modifications:
* If applicable, add the following below the License Header, with the fields
* enclosed by brackets [] replaced by your own identifying information:
* "Portions Copyright [year] [name of copyright owner]"
*
* Contributor(s):
* If you wish your version of this file to be governed by only the CDDL or
* only the GPL Version 2, indicate your decision by adding "[Contributor]
* elects to include this software in this distribution under the [CDDL or GPL
* Version 2] license." If you don't indicate a single choice of license, a
* recipient has the option to distribute your version of this file under
* either the CDDL, the GPL Version 2 or to extend the choice of license to
* its licensees as provided above. However, if you add GPL Version 2 code
* and therefore, elected the GPL Version 2 license, then the option applies
* only if the new code is made subject to such option by the copyright
* holder.
*/
package com.sun.tools.xjc.reader.gbind;
/**
* {@link Expression} that represents a concatanation of two expressions
* "A,B".
*
* @author Kohsuke Kawaguchi
*/
public final class Sequence extends Expression {
/**
* 'A' of 'A,B'
*/
private final Expression lhs;
/**
* 'B' of 'A,B'
*/
private final Expression rhs;
/**
* Compute this value eagerly for better performance
*/
private final boolean isNullable;
/**
* Cached value of {@link #lastSet()} for better performance.
* Sequence tends to be where the recursive lastSet computation occurs.
*/
private ElementSet lastSet;
public Sequence(Expression lhs, Expression rhs) {
this.lhs = lhs;
this.rhs = rhs;
isNullable = lhs.isNullable() && rhs.isNullable();
}
ElementSet lastSet() {
if(lastSet==null) {
if(rhs.isNullable())
lastSet = ElementSets.union(lhs.lastSet(),rhs.lastSet());
else
lastSet = rhs.lastSet();
}
return lastSet;
}
boolean isNullable() {
return isNullable;
}
void buildDAG(ElementSet incoming) {
lhs.buildDAG(incoming);
if(lhs.isNullable())
rhs.buildDAG(ElementSets.union(incoming,lhs.lastSet()));
else
rhs.buildDAG(lhs.lastSet());
}
public String toString() {
return '('+lhs.toString()+','+rhs.toString()+')';
}
}