请简要说明下面程序片断功能。 public static final int TABLE1_DIR = 0; public static final int TABLE1_ITEM = 1; public static final int TABLE2_DIR = 2; public static final int TABLE2_ITEM = 3; private static UriMatcher uriMatcher; static { uriMatcher = new UriMatcher(UriMatcher.NO_MATCH); uriMatcher.addURI("com.example.app.provider", "table1", TABLE1_DIR); uriMatcher.addURI("com.example.app.provider ", "table1/#", TABLE1_ITEM); uriMatcher.addURI("com.example.app.provider ", "table2", TABLE2_ITEM); uriMatcher.addURI("com.example.app.provider ", "table2/#", TABLE2_ITEM); }