OrderBy.java

/*
 * Copyright 1999-2012 Alibaba Group.
 * 
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
 * in compliance with the License. You may obtain a copy of the License at
 * 
 * http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software distributed under the License
 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
 * or implied. See the License for the specific language governing permissions and limitations under
 * the License.
 */
/**
 * (created at 2011-1-25)
 */
package fm.liu.timo.parser.ast.fragment;

import java.util.ArrayList;
import java.util.LinkedList;
import java.util.List;
import fm.liu.timo.parser.ast.ASTNode;
import fm.liu.timo.parser.ast.expression.Expression;
import fm.liu.timo.parser.util.Pair;
import fm.liu.timo.parser.visitor.Visitor;

/**
 * @author <a href="mailto:shuo.qius@alibaba-inc.com">QIU Shuo</a>
 */
public class OrderBy implements ASTNode {
    /** might be {@link LinkedList} */
    private final List<Pair<Expression, SortOrder>> orderByList;

    public List<Pair<Expression, SortOrder>> getOrderByList() {
        return orderByList;
    }

    /**
     * performance tip: linked list is used
     */
    public OrderBy() {
        this.orderByList = new LinkedList<Pair<Expression, SortOrder>>();
    }

    /**
     * performance tip: expect to have only 1 order item
     */
    public OrderBy(Expression expr, SortOrder order) {
        this.orderByList = new ArrayList<Pair<Expression, SortOrder>>(1);
        this.orderByList.add(new Pair<Expression, SortOrder>(expr, order));
    }

    public OrderBy(List<Pair<Expression, SortOrder>> orderByList) {
        if (orderByList == null)
            throw new IllegalArgumentException("order list is null");
        this.orderByList = orderByList;
    }

    public OrderBy addOrderByItem(Expression expr, SortOrder order) {
        orderByList.add(new Pair<Expression, SortOrder>(expr, order));
        return this;
    }

    @Override
    public void accept(Visitor visitor) {
        visitor.visit(this);
    }
}