DoubleKeyMap.java

/*
 * [The "BSD license"]
 *  Copyright (c) 2012 Terence Parr
 *  Copyright (c) 2012 Sam Harwell
 *  All rights reserved.
 *
 *  Redistribution and use in source and binary forms, with or without
 *  modification, are permitted provided that the following conditions
 *  are met:
 *
 *  1. Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
 *  2. Redistributions in binary form must reproduce the above copyright
 *     notice, this list of conditions and the following disclaimer in the
 *     documentation and/or other materials provided with the distribution.
 *  3. The name of the author may not be used to endorse or promote products
 *     derived from this software without specific prior written permission.
 *
 *  THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 *  IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 *  OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 *  IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 *  INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 *  NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 *  DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 *  THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 *  (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 *  THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

package org.antlr.v4.runtime.misc;

import java.util.Collection;
import java.util.LinkedHashMap;
import java.util.Map;
import java.util.Set;

/** Sometimes we need to map a key to a value but key is two pieces of data.
 *  This nested hash table saves creating a single key each time we access
 *  map; avoids mem creation.
 */
public class DoubleKeyMap<Key1, Key2, Value> {
	Map<Key1, Map<Key2, Value>> data = new LinkedHashMap<Key1, Map<Key2, Value>>();

	public Value put(Key1 k1, Key2 k2, Value v) {
		Map<Key2, Value> data2 = data.get(k1);
		Value prev = null;
		if ( data2==null ) {
			data2 = new LinkedHashMap<Key2, Value>();
			data.put(k1, data2);
		}
		else {
			prev = data2.get(k2);
		}
		data2.put(k2, v);
		return prev;
	}

	public Value get(Key1 k1, Key2 k2) {
		Map<Key2, Value> data2 = data.get(k1);
		if ( data2==null ) return null;
		return data2.get(k2);
	}

	public Map<Key2, Value> get(Key1 k1) { return data.get(k1); }

	/** Get all values associated with primary key */
	public Collection<Value> values(Key1 k1) {
		Map<Key2, Value> data2 = data.get(k1);
		if ( data2==null ) return null;
		return data2.values();
	}

	/** get all primary keys */
	public Set<Key1> keySet() {
		return data.keySet();
	}

	/** get all secondary keys associated with a primary key */
	public Set<Key2> keySet(Key1 k1) {
		Map<Key2, Value> data2 = data.get(k1);
		if ( data2==null ) return null;
		return data2.keySet();
	}
}