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StackArrayList.java
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113 lines (97 loc) · 2.64 KB
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package DataStructures.Stacks;
import java.util.ArrayList;
import java.util.EmptyStackException;
/**
* This class implements a Stack using an ArrayList.
* <p>
* A stack is exactly what it sounds like. An element gets added to the top of
* the stack and only the element on the top may be removed.
* <p>
* This is an ArrayList Implementation of a stack, where size is not
* a problem we can extend the stack as much as we want.
*/
public class StackArrayList {
/**
* Driver Code
*/
public static void main(String[] args) {
StackArrayList stack = new StackArrayList();
assert stack.isEmpty();
for (int i = 1; i <= 5; ++i) {
stack.push(i);
assert stack.size() == i;
}
assert stack.size() == 5;
assert stack.peek() == 5 && stack.pop() == 5 && stack.peek() == 4;
/* pop elements at the top of this stack one by one */
while (!stack.isEmpty()) {
stack.pop();
}
assert stack.isEmpty();
try {
stack.pop();
assert false; /* this should not happen */
} catch (EmptyStackException e) {
assert true; /* this should happen */
}
}
/**
* ArrayList representation of the stack
*/
private ArrayList<Integer> stack;
/**
* Constructor
*/
public StackArrayList() {
stack = new ArrayList<>();
}
/**
* Adds value to the end of list which
* is the top for stack
*
* @param value value to be added
*/
public void push(int value) {
stack.add(value);
}
/**
* Removes the element at the top of this stack and returns
*
* @return Element popped
* @throws EmptyStackException if the stack is empty.
*/
public int pop() {
if (isEmpty()) {
throw new EmptyStackException();
}
/* remove the element on the top of the stack */
return stack.remove(stack.size() - 1);
}
/**
* Test if the stack is empty.
*
* @return {@code true} if this stack is empty, {@code false} otherwise.
*/
public boolean isEmpty() {
return stack.isEmpty();
}
/**
* Return the element at the top of this stack without removing it from the stack.
*
* @return the element at the top of this stack.
*/
public int peek() {
if (isEmpty()) {
throw new EmptyStackException();
}
return stack.get(stack.size() - 1);
}
/**
* Return size of this stack.
*
* @return size of this stack.
*/
public int size() {
return stack.size();
}
}