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import java.util.NoSuchElementException;

class DynamicStack {

private String[] stack;

private int top;

public DynamicStack() {

top = 0;

stack = new String[2];

}

private void resize(int capacity) {

String[] copy = new String[capacity];

for (int i = 0; i < top; ++i) {

copy[i] = stack[i];

}

stack = copy;

}

public int size() {

return top;

}

public boolean isEmpty() {

return top == 0;

}

public void push(String s) {

if (top == stack.length) {

resize(stack.length * 2);

}

stack[top++] = s;

}

public String pop() {

if (isEmpty()) {

throw new NoSuchElementException("Stack underflow");

}

String item = stack[top - 1];

stack[top - 1] = null;

top--;

if (top > 0 && top == stack.length / 4) {

resize(stack.length / 2);

}

return item;

}

public static void main(String[] args) {

String[] string = {"a", "b", "c", "d", "e"};

DynamicStack stack = new DynamicStack();

System.out.println("IsEmpty : " + stack.isEmpty() + ", size: " + stack.size());

for (String s : string) {

System.out.print("Push : " + s + " , ");

stack.push(s);

System.out.println("IsEmpty : " + stack.isEmpty() + ", size: " + stack.size());

}

while(!stack.isEmpty()) {

System.out.print("Pop : " + stack.pop() + " ");

System.out.println("IsEmpty : " + stack.isEmpty() + ", size: " + stack.size());

}

System.out.println("IsEmpty : " + stack.isEmpty() + ", size: " + stack.size());

}

}