Java Data Structure Cheat Sheet - Stack

Stack exists as a class (not as an interface or abstract class) in Java.

https://docs.oracle.com/javase/7/docs/api/java/util/Stack.html

Here are the three main methods:

• E peek()
• E pop()
• E push(E item)

They are all O(1).

Example:

import java.util.Stack;

public class StackExample {

  public static void main(String[] args) {
    Stack<Integer> s = new Stack<Integer>();

    s.push(1); // add is also available as Vector
    s.push(2);
    s.push(3);

    System.out.println(s.peek()); // 3

    while (!s.empty()) { // isEmpty() is also available as Vector
      int n = s.pop();
      System.out.println(n); // 3, 2, 1
    }

    // System.out.println(s.peek()); // java.util.EmptyStackException is called
  }
}