Data update

Task/Stack/Ballerina/stack-1.ballerina

@@ -0,0 +1,15 @@
+import ballerina/io;
+
+public function main() {
+    int[] stack = [];
+    stack.push(1);
+    stack.push(2);
+    io:println("Stack contains ", stack);
+    io:println("Number of elements in stack = ", stack.length());
+    int item = stack.pop();
+    io:println(item, " popped from the stack");
+    io:println("Last element is now ", stack[stack.length() - 1]);
+    stack.removeAll();
+    io:println("Stack cleared");
+    io:println("Is stack now empty? ", stack.length() == 0 ? "yes" : "no");
+}

Task/Stack/Ballerina/stack-2.ballerina

@@ -0,0 +1,53 @@
+import ballerina/io;
+
+class Stack {
+    private any[] s = [];
+
+    function push(any a) {
+        self.s.push(a);
+    }
+
+    function length() returns int {
+        return self.s.length();
+    }
+
+    function isEmpty() returns boolean {
+        return self.length() == 0;
+    }
+
+    function pop() returns any? {
+        if !self.isEmpty() {
+            return self.s.pop();
+        }
+        return ();
+    }
+
+    function peek() returns any? {
+        if !self.isEmpty() {
+            return self.s[self.length() - 1];
+        }
+        return ();
+    }
+
+    function clear() {
+        self.s.removeAll();
+    }
+
+    function toString() returns string {
+        return self.s.toString();
+    }
+}
+
+public function main() {
+    Stack s = new;
+    s.push(1);
+    s.push(2);
+    io:println("Stack contains ", s);
+    io:println("Number of elements in stack = ", s.length());
+    any item = s.pop();
+    io:println(item, " popped from the stack");
+    io:println("Last element is now ", s.peek());
+    s.clear();
+    io:println("Stack cleared");
+    io:println("Is stack now empty? ", s.isEmpty() ? "yes" : "no");
+}