error handling

queue/main.cpp

@@ -4,20 +4,27 @@ int main(void){
 	ios_base::sync_with_stdio(false);
 	cin.tie(NULL);
 	Queue<int>* q = new Queue<int>();
-	cout << "newest:" << q->frontEle() << endl;
-	cout << "oldest:" << q->backEle() << endl;
-	cout << "size: " << q->returnSize() << endl;
-	q->popEle();
-	q->PushEle(1);
-	q->PushEle(2);
-	q->PushEle(3);
-	cout << "newest:" << q->frontEle() << endl;
-	cout << "oldest:" << q->backEle() << endl;
-	cout << "size: " << q->returnSize() << endl;
-	q->printQueue();
-	q->popEle();
-	q->printQueue();
-	cout << "newest:" << q->frontEle() << endl;
-	cout << "oldest:" << q->backEle() << endl;
-	cout << "size: " << q->returnSize() << endl;
+	try
+	{
+		cout << "newest:" << q->frontEle() << endl;
+		cout << "oldest:" << q->backEle() << endl;
+		cout << "size: " << q->returnSize() << endl;
+		q->popEle();
+		q->PushEle(1);
+		q->PushEle(2);
+		q->PushEle(3);
+		cout << "newest:" << q->frontEle() << endl;
+		cout << "oldest:" << q->backEle() << endl;
+		cout << "size: " << q->returnSize() << endl;
+		q->printQueue();
+		q->popEle();
+		q->printQueue();
+		cout << "newest:" << q->frontEle() << endl;
+		cout << "oldest:" << q->backEle() << endl;
+		cout << "size: " << q->returnSize() << endl;
+	}
+	catch(const std::exception& e)
+	{
+		std::cerr << e.what() << '\n';
+	}
 }

queue/queue.cpp

@@ -77,25 +77,13 @@ void Queue<T>::popEle(void){
 
 template <typename T>
 T Queue<T>::frontEle(void){
-	try{
-		if(size <= 0) throw "Queue is empty";
-	}
-	catch (const char* str){
-		cout << str << endl;
-		return EXIT_FAILURE;
-	}
+	if(size <= 0) throw QueueEmptyException();
 	return last->data;
 }
 
 template <typename T>
 T Queue<T>::backEle(void){
-	try{
-		if(size <= 0) throw "Queue is empty";
-	}
-	catch (const char* str){
-		cout << str << endl;
-		return EXIT_FAILURE;
-	}
+	if(size <= 0) throw QueueEmptyException();
 	return this->next->data; 
 }
 
@@ -109,3 +97,15 @@ void Queue<T>::printQueue(void){
 	cout << endl;
 	return;
 }
+
+
+
+QueueEmptyException::QueueEmptyException()
+: message("Queue is Empty"){}
+
+QueueEmptyException::QueueEmptyException(string _m)
+: message("" + _m){}
+
+const char * QueueEmptyException::what() const throw(){
+	return message.c_str();
+}

queue/queue.h

@@ -17,3 +17,13 @@ class Queue{
 	static Queue* last;
 	static int size;
 };
+
+class QueueEmptyException:public exception
+{
+private:
+	string message;
+public:
+	QueueEmptyException();
+	QueueEmptyException(string);
+	virtual const char* what() const throw();
+};