BufferPool is done. Waiting for test.
During compiling, there is an error. It is fixed by omit the 'static' modifier of CatalogHeap class. The following is the compile results.
    [javac] Compiling 17 source files to /home/darkangle/course_work/cs186/project1/bin/src
    [javac] /home/darkangle/course_work/cs186/project1/src/java/simpledb/Catalog.java:97: error: no enclosing instance of type Catalog is in scope
    [javac]       public CatalogHeap(DbFile file, String tname, String pkey, TupleDesc tds){
    [javac]
Mon Jul 28 00:17:18 CST 2014