private ExpressionNode parseExpression() throws ParseExpressionException {
ExpressionNode rootNode = null;
rootNode = parseTerm();
scanner.nextSymbol();
while (isLogicalOp()) {
if (scanner.isAnd()) {
ExpressionNode oldRootNode = rootNode;
rootNode = new ExpressionAndNode(oldRootNode, parseTerm());
} else if (scanner.isOr()) {
ExpressionNode oldRootNode = rootNode;
rootNode = new ExpressionOrNode(oldRootNode, parseTerm());
} else {
throw new ParseExpressionException();
}
}
return rootNode;
}
private boolean isLogicalOp() {
return (scanner.isAnd() || scanner.isOr());
}
