if (expStack.size() < 2) {
// When ) comes we expect atleast a ( node and another leaf/non leaf node
// in stack.
throw new ParseException();
} else {
ExpressionNode top = expStack.pop();
ExpressionNode secondTop = expStack.pop();
// The second top must be a ( node and top should not be a ). Top can be
// any thing else
if (top == LeafExpressionNode.OPEN_PARAN_NODE
|| secondTop != LeafExpressionNode.OPEN_PARAN_NODE) {
throw new ParseException("Error parsing expression " + expS + " at column : " + index);
}
// a&(b|) is not valid.
// The top can be a ! node but with exactly child nodes. !).. is invalid
// Other NonLeafExpressionNode , then there should be exactly 2 child.
// (a&) is not valid.
if (top instanceof NonLeafExpressionNode) {
NonLeafExpressionNode nlTop = (NonLeafExpressionNode) top;
if ((nlTop.getOperator() == Operator.NOT && nlTop.getChildExps().size() != 1)
|| (nlTop.getOperator() != Operator.NOT && nlTop.getChildExps().size() != 2)) {
throw new ParseException("Error parsing expression " + expS + " at column : " + index);
}
}
// When (a|b)&(c|d) comes while processing the second ) there will be
// already (a|b)& node
// avail in the stack. The top will be c|d node. We need to take it out
// and combine as one
// node.
if (!expStack.isEmpty()) {
ExpressionNode thirdTop = expStack.peek();
if (thirdTop instanceof NonLeafExpressionNode) {
NonLeafExpressionNode nlThirdTop = (NonLeafExpressionNode) expStack.pop();
nlThirdTop.addChildExp(top);
if (nlThirdTop.getOperator() == Operator.NOT) {
// It is a NOT node. So there may be a NonLeafExpressionNode below
// it to which the
// completed NOT can be added now.
if (!expStack.isEmpty()) {
ExpressionNode fourthTop = expStack.peek();
if (fourthTop instanceof NonLeafExpressionNode) {
// Its Operator will be OR or AND
NonLeafExpressionNode nlFourthTop = (NonLeafExpressionNode) fourthTop;
assert nlFourthTop.getOperator() != Operator.NOT;
// Also for sure its number of children will be 1