Java Language Queues and Deques Stacks
Example
What is a Stack?
In Java, Stacks are a LIFO (Last In, First Out) Data structure for objects.
Stack API
Java contains a Stack API with the following methods
Stack() //Creates an empty Stack
isEmpty() //Is the Stack Empty? Return Type: Boolean
push(Item item) //push an item onto the stack
pop() //removes item from top of stack Return Type: Item
size() //returns # of items in stack Return Type: Int
Example
import java.util.*;
public class StackExample {
public static void main(String args[]) {
Stack st = new Stack();
System.out.println("stack: " + st);
st.push(10);
System.out.println("10 was pushed to the stack");
System.out.println("stack: " + st);
st.push(15);
System.out.println("15 was pushed to the stack");
System.out.println("stack: " + st);
st.push(80);
System.out.println("80 was pushed to the stack");
System.out.println("stack: " + st);
st.pop();
System.out.println("80 was popped from the stack");
System.out.println("stack: " + st);
st.pop();
System.out.println("15 was popped from the stack");
System.out.println("stack: " + st);
st.pop();
System.out.println("10 was popped from the stack");
System.out.println("stack: " + st);
if(st.isEmpty())
{
System.out.println("empty stack");
}
}
}
This Returns:
stack: []
10 was pushed to the stack
stack: [10]
15 was pushed to the stack
stack: [10, 15]
80 was pushed to the stack
stack: [10, 15, 80]
80 was popped from the stack
stack: [10, 15]
15 was popped from the stack
stack: [10]
10 was popped from the stack
stack: []
empty stack
