ChildrenCache.java

package zx.soft.zookeeper.book;

import java.util.ArrayList;
import java.util.List;

/**
 * Auxiliary cache to handle changes to the lists of tasks and of workers.
 * 
 * @author wanggang
 *
 */
public class ChildrenCache {

	protected List<String> children;

	ChildrenCache() {
		this.children = null;
	}

	ChildrenCache(List<String> children) {
		this.children = children;
	}

	List<String> getList() {
		return children;
	}

	List<String> addedAndSet(List<String> newChildren) {
		ArrayList<String> diff = null;

		if (children == null) {
			diff = new ArrayList<String>(newChildren);
		} else {
			for (String s : newChildren) {
				if (!children.contains(s)) {
					if (diff == null) {
						diff = new ArrayList<String>();
					}

					diff.add(s);
				}
			}
		}
		this.children = newChildren;

		return diff;
	}

	List<String> removedAndSet(List<String> newChildren) {
		List<String> diff = null;

		if (children != null) {
			for (String s : children) {
				if (!newChildren.contains(s)) {
					if (diff == null) {
						diff = new ArrayList<String>();
					}

					diff.add(s);
				}
			}
		}
		this.children = newChildren;

		return diff;
	}

}