these lines appears in the generated file of .jj file
ASTSQLSchemaStatement jjtn000 = new ASTSQLSchemaStatement(JJTSQLSCHEMASTATEMENT);
boolean jjtc000 = true;
jjtree.openNodeScope(jjtn000);
Together they create a new node and open its scope. (And declare a boolean var.) The node's scope will remain open until it is closed or abandoned. While it is open, it may acquire children. When it is closed it will be pushed on a stack and may become the child of some other open node. See https://javacc.java.net/doc/JJTree.html for more details.