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import java.lang.IndexOutOfBoundsException;
import java.util.Arrays;
public class Stack {
private int max;
private int top;
private Object[] list;
public Stack() {
max = 512;
top = 0;
list = new Object[max];
}
public Stack(int size) {
max = size;
top = 0;
list = new Object[max];
}
@SuppressWarnings("unchecked")
public boolean isEmpty() {
for(E t : (E[]) list) {
if(t != null) {
return false;
}
}
return true;
}
@SuppressWarnings("unchecked")
public E peek() {
return (E) list[top];
}
@SuppressWarnings("unchecked")
public int size() {
if(top == 0) {
return 0;
}
int count = 0;
for(E t : (E[]) list) {
if(t != null) {
count++;
}
}
return count;
}
@SuppressWarnings("unchecked")
public E pop() {
if(isEmpty()) {
throw new IndexOutOfBoundsException("This stack is empty; nothing to pop.");
}
E data = (E) list[top];
top = (top == 0 ? 0 : top - 1);
return data;
}
public void push(E data) {
if(top == max - 1) {
list = Arrays.copyOf(list, list.length * 2);
}
top++;
list[top] = data;
}
}