package com.coding.weak1;
import java.util.ArrayList;
import java.util.NoSuchElementException;
public class Stack {
private ArrayList elementData = new ArrayList();
public void push(Object o){
elementData.add(o);
}
public Object pop(){
if(isEmpty()){
throw new NoSuchElementException();
}
return elementData.remove(elementData.size() - 1);
}
public Object peek(){
if (size() == 0)
return null;
return elementData.get(elementData.size()-1);
}
public boolean isEmpty(){
return elementData.size() == 0;
}
public int size(){
return elementData.size();
}
@Override
public String toString() {
StringBuilder sb = new StringBuilder();
if (isEmpty()) {
return "";
}
for (int i = elementData.size() - 1; i >= 0; i--) {
sb.append(elementData.get(i).toString());
sb.append(",");
}
return sb.substring(0, sb.lastIndexOf(","));
}
}