import com.hp.hpl.jena.sparql.algebra.op.OpN; //导入依赖的package包/类
@Override
   protected void visitN(OpN op) {
for (Iterator<Op> iter = op.iterator(); iter.hasNext();) {
    Op sub = iter.next();
    sub.visit(this);
}
op.visit(visitor);
   }
 

import com.hp.hpl.jena.sparql.algebra.op.OpN; //导入依赖的package包/类
@Override
protected void visitN(OpN op)
{
	if ( topDown ) op.visit(visitor);
	for ( Iterator<Op> iter = op.iterator() ; iter.hasNext() ; )
	{
		Op sub = iter.next();
		sub.visit(this);
	}
	if ( !topDown ) op.visit(visitor);
}
 

import com.hp.hpl.jena.sparql.algebra.op.OpN; //导入依赖的package包/类
private void wrapInCurrentFilterAndRecurse(OpN opN) {
	List<Expr> retainedFilterExpr = new ArrayList<Expr>(filterExpr);
	filterExpr.clear();
	List<Op> children = new ArrayList<Op>();
	for (Op child : opN.getElements()) {
		child.visit(this);
		children.add(stack.pop());
	}
	wrapInFilter(opN.apply(copy, children), retainedFilterExpr);
	filterExpr = retainedFilterExpr;
}
 

import com.hp.hpl.jena.sparql.algebra.op.OpN; //导入依赖的package包/类
private Op substitute(OpN op, List<Op> elts) {
	// Need to do one-deep equality checking.
	if ( equals1(elts, op.getElements()))
		return op;
	return op.copy(elts);
}