In this article, we will discuss Stack class in detail
Key points about Stack:
- Stack is a legacy class
- introduced in Java 1.0 version
- works in Last-In First-Out order (LIFO order)
- most of its methods are synchronized i.e.; thread-safe
1. Stack:
- Stack is a sub-class of Vector (i.e.; Stack extends Vector)
- All properties are same as that of Vector class
- Its data structure is designed in such a way that elements added last to the Stack will be returned first
- That is, it follows Last-In First-Out order
- Present in java.util package and extends java.util.Vector class
2. Stack constructors:
Stack s = new Stack();
- Stack defines default constructor which creates an empty Stack object
3. Stack methods:
- Stack specific methods
| Stack methods | Description |
| Object push(Object obj); | add/inserts new element/object into stack |
| Object pop(); | removes and return top of the stack |
| Object peek(); | returns top of the stack (just returns but doesn’t remove unlike pop() operation |
| boolean empty(); | check whether invoking stack is empty or not returns true, if stack is empty; otherwise, false |
| int search(Object obj) | searches specified element/object from invoking stack
returns offset from top of the stack, if element is available; otherwise returns -1, if element not available |
4. Stack examples:
StackPushAndPop.java
package in.bench.resources.java.collection;
import java.util.Stack;
public class StackPushAndPop {
public static void main(String[] args) {
// creating Stack object of type String
Stack<String> stk = new Stack<String>();
// adding elements to Stack object
stk.push("Sundar Pichai");
stk.push("Satya Nadella");
stk.push("Shiv Nadar");
stk.push("Shantanu Narayen");
stk.push("Francisco D’Souza");
System.out.println("Iterating Stack values\n");
// Iterating using enhanced for-loop
for(String str : stk){
System.out.println(str);
}
// peeking top of the stack - doesn't remove
String peekStr = stk.peek();
System.out.println("\n\nElement peeked at top "
+ "of the Stack : " + peekStr);
// removing top element of the Stack
String poppedStr = stk.pop();
System.out.println("\n\nElement removed at top "
+ "of the Stack : " + poppedStr);
// check whether Stack is empty
boolean isStackEmpty = stk.empty();
System.out.println("\n\nWhether Stack is Empty : "
+ isStackEmpty);
// to print all values of Stack
System.out.println("\n\nStack values after removing "
+ "top of the Stack \n" + stk);
}
}
Output:
Iterating Stack values
Sundar Pichai
Satya Nadella
Shiv Nadar
Shantanu Narayen
Francisco D’Souza
Element peeked at top of the Stack : Francisco D’Souza
Element removed at top of the Stack : Francisco D’Souza
Whether Stack is Empty : false
Stack values after removing top of the Stack
[Sundar Pichai, Satya Nadella, Shiv Nadar, Shantanu Narayen]
Note: All methods of Stack are synchronized hence it is thread-safe
References:
- https://docs.oracle.com/javase/tutorial/collections/intro/
- https://docs.oracle.com/javase/tutorial/collections/interfaces/collection.html
- https://docs.oracle.com/javase/7/docs/api/java/util/Collection.html
- https://docs.oracle.com/javase/tutorial/collections/interfaces/list.html
- https://docs.oracle.com/javase/7/docs/api/java/util/List.html
- https://docs.oracle.com/javase/8/docs/api/java/util/List.html
- https://docs.oracle.com/javase/7/docs/api/java/util/Vector.html
- https://docs.oracle.com/javase/8/docs/api/java/util/Vector.html
- https://docs.oracle.com/javase/7/docs/api/java/util/Stack.html
Happy Coding !!
Happy Learning !!
