lucene基础有关问题

lucene基础问题
RAMDirectory ram=new RAMDirectory();
IndexWriter indexWriter = new IndexWriter(ram,new StandardAnalyzer(),true); 
错误为：Default constructor cannot handle exception type LockObtainFailedException 
 thrown by implicit super constructor. Must define an explicit constructor
和书本上代码一样，怎么会有错误？

[解决办法]
需要处理 LockObtainFailedException 这个异常