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3.3.6 Linked Lists
Before implementing the linked representation of stacks. Let’s first study how to create linked representation. In particular, we’ll be looking at linked lists.
The linked list is a dynamic structure as opposed to the array, which is a static structure. This means that the linked list can grow and shrink in size depending on the need of the
user. A linked list is defined as a collection of nodes, each of which consists of some data and a link or a pointer to the next node in the list.
The figure below shows how a node looks like.
Figure 3.3: A node
Here is an example of a non-empty linked list with three nodes.
Figure 3.4: A non-empty linked list with three nodes
Here is how the node class is implemented. This class can be used to create linked lists. class Node {
int data; integer data contained in the node Node nextNode; the next node in the list
}
class TestNode { public static void mainString args[] {
Node emptyList = null; create an empty list head points to 1st node in the list
Node head = new Node; initialize 1st node in the list
head.data = 5; head.nextNode = new Node;
head.nextNode.data = 10; null marks the end of the list
head.nextNode.nextNode = null; print elements of the list
Node currNode = head; while currNode = null {
System.out.printlncurrNode.data; currNode = currNode.nextNode;
} }
}
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Here is a trace of TestNodes main method.
Figure 3.5: Trace of TestNode Introduction to Programming II
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3.3.7 Linked Representation of an Integer Stack
Now that you’ve learned about linked list. You’re now ready to apply what you’ve learned to implement the linked representation of a stack.
class DynamicIntStack{ private IntStackNode top; head or top of the stack
class IntStackNode { node class int data;
IntStackNode next; IntStackNodeint n {
data = n; next = null;
} }
void pushint n{ no need to check for overflow
IntStackNode node = new IntStackNoden; node.next = top;
top = node; }
int pop { if isEmpty {
return -1; may throw a user-defined exception
} else { int n = top.data;
top = top.next; return n;
} }
boolean isEmpty{ return top == null;
} public static void mainString args[] {
DynamicIntStack myStack = new DynamicIntStack; myStack.push5;
myStack.push10; print elements of the stack
IntStackNode currNode = myStack.top; while currNode=null {
System.out.printlncurrNode.data; currNode = currNode.next;
} System.out.printlnmyStack.pop;
System.out.printlnmyStack.pop; }
}
Here is the expected output of the code:
Figure 3.6: Expected Output of DynamicStack
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Figure 3.7: Trace of DynamicStack
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3.3.8 Java Collections
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