Java stack add push

Java stack add push

The Stack class represents a last-in-first-out (LIFO) stack of objects. It extends class Vector with five operations that allow a vector to be treated as a stack. The usual push and pop operations are provided, as well as a method to peek at the top item on the stack, a method to test for whether the stack is empty , and a method to search the stack for an item and discover how far it is from the top. When a stack is first created, it contains no items. A more complete and consistent set of LIFO stack operations is provided by the Deque interface and its implementations, which should be used in preference to this class. For example:

 Deque stack = new ArrayDeque();

Field Summary

Fields declared in class java.util.Vector

Fields declared in class java.util.AbstractList

Constructor Summary

Method Summary

Methods declared in class java.util.Vector

Methods declared in class java.lang.Object

Methods declared in interface java.util.Collection

Methods declared in interface java.util.List

Constructor Detail

Stack

Method Detail

push

pop

peek

empty

search

Returns the 1-based position where an object is on this stack. If the object o occurs as an item in this stack, this method returns the distance from the top of the stack of the occurrence nearest the top of the stack; the topmost item on the stack is considered to be at distance 1 . The equals method is used to compare o to the items in this stack.

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Copyright © 1993, 2023, Oracle and/or its affiliates, 500 Oracle Parkway, Redwood Shores, CA 94065 USA.
All rights reserved. Use is subject to license terms and the documentation redistribution policy.

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Class Stack

The Stack class represents a last-in-first-out (LIFO) stack of objects. It extends class Vector with five operations that allow a vector to be treated as a stack. The usual push and pop operations are provided, as well as a method to peek at the top item on the stack, a method to test for whether the stack is empty , and a method to search the stack for an item and discover how far it is from the top.

When a stack is first created, it contains no items.

A more complete and consistent set of LIFO stack operations is provided by the Deque interface and its implementations, which should be used in preference to this class. For example:

 Deque stack = new ArrayDeque();

Field Summary

Fields declared in class java.util.Vector

Fields declared in class java.util.AbstractList

Constructor Summary

Method Summary

Methods declared in class java.util.Vector

Methods declared in class java.lang.Object

Methods declared in interface java.util.Collection

Methods declared in interface java.util.List

Constructor Details

Stack

Method Details

push

pop

peek

empty

search

Returns the 1-based position where an object is on this stack. If the object o occurs as an item in this stack, this method returns the distance from the top of the stack of the occurrence nearest the top of the stack; the topmost item on the stack is considered to be at distance 1 . The equals method is used to compare o to the items in this stack.

Report a bug or suggest an enhancement
For further API reference and developer documentation see the Java SE Documentation, which contains more detailed, developer-targeted descriptions with conceptual overviews, definitions of terms, workarounds, and working code examples. Other versions.
Java is a trademark or registered trademark of Oracle and/or its affiliates in the US and other countries.
Copyright © 1993, 2023, Oracle and/or its affiliates, 500 Oracle Parkway, Redwood Shores, CA 94065 USA.
All rights reserved. Use is subject to license terms and the documentation redistribution policy.

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Java Stack Class Tutorial with Examples

A Stack is a Last In First Out (LIFO) data structure. It supports two basic operations called push and pop. The push operation adds an element at the top of the stack, and the pop operation removes an element from the top of the stack.

Java provides a Stack class which models the Stack data structure. The Stack class is part of Java’s collections framework. Following is the class hierarchy of Stack in Java —

The Stack class extends Vector which implements the List interface. A Vector is a re-sizable collection. It grows its size to accommodate new elements and shrinks the size when the elements are removed.

Since the Stack class extends Vector , it also grows and shrinks its size as needed when new elements are added or removed.

Creating a Stack and Performing basic operations like push, pop and peek

import java.util.Stack; public class StackExample  public static void main(String[] args)  // Creating a Stack StackString> stackOfCards = new Stack>(); // Pushing new items to the Stack stackOfCards.push("Jack"); stackOfCards.push("Queen"); stackOfCards.push("King"); stackOfCards.push("Ace"); System.out.println("Stack => " + stackOfCards); System.out.println(); // Popping items from the Stack String cardAtTop = stackOfCards.pop(); // Throws EmptyStackException if the stack is empty System.out.println("Stack.pop() => " + cardAtTop); System.out.println("Current Stack => " + stackOfCards); System.out.println(); // Get the item at the top of the stack without removing it cardAtTop = stackOfCards.peek(); System.out.println("Stack.peek() => " + cardAtTop); System.out.println("Current Stack => " + stackOfCards); > >

# Output Stack => [Jack, Queen, King, Ace] Stack.pop() => Ace Current Stack => [Jack, Queen, King] Stack.peek() => King Current Stack => [Jack, Queen, King]

• Check if the stack is empty.
• Find the size of the stack.
• Search for an element in the Stack.

import java.util.Stack; public class StackSizeSearchExample  public static void main(String[] args)  StackString> stackOfCards = new Stack>(); stackOfCards.push("Jack"); stackOfCards.push("Queen"); stackOfCards.push("King"); stackOfCards.push("Ace"); System.out.println("Stack : " + stackOfCards); // Check if the Stack is empty System.out.println("Is Stack empty? : " + stackOfCards.isEmpty()); // Find the size of Stack System.out.println("Size of Stack : " + stackOfCards.size()); // Search for an element // The search() method returns the 1-based position of the element from the top of the stack // It returns -1 if the element was not found in the stack int position = stackOfCards.search("Queen"); if(position != -1)  System.out.println("Found the element \"Queen\" at position : " + position); > else  System.out.println("Element not found"); > > >

# Output Stack : [Jack, Queen, King, Ace] Is Stack empty? : false Size of Stack : 4 Found the element "Queen" at position : 3

The example in this section shows various ways of iterating over a Stack.

• Iterate over a Stack using Java 8 forEach().
• Iterate over a Stack using iterator().
• Iterate over a Stack using iterator() and Java 8 forEachRemaining() method.
• Iterate over a Stack from Top to Bottom using listIterator().

import java.util.Iterator; import java.util.ListIterator; import java.util.Stack; public class IterateOverStackExample  public static void main(String[] args)  StackString> stackOfPlates = new Stack>(); stackOfPlates.add("Plate 1"); stackOfPlates.add("Plate 2"); stackOfPlates.add("Plate 3"); stackOfPlates.add("Plate 4"); System.out.println("=== Iterate over a Stack using Java 8 forEach() method ==="); stackOfPlates.forEach(plate ->  System.out.println(plate); >); System.out.println("\n=== Iterate over a Stack using iterator() ==="); IteratorString> platesIterator = stackOfPlates.iterator(); while (platesIterator.hasNext())  String plate = platesIterator.next(); System.out.println(plate); > System.out.println("\n=== Iterate over a Stack using iterator() and Java 8 forEachRemaining() method ==="); platesIterator = stackOfPlates.iterator(); platesIterator.forEachRemaining(plate ->  System.out.println(plate); >); System.out.println("\n=== Iterate over a Stack from TOP to BOTTOM using listIterator() ==="); // ListIterator allows you to traverse in both forward and backward directions. // We'll start from the top of the stack and traverse backwards. ListIteratorString> platesListIterator = stackOfPlates.listIterator(stackOfPlates.size()); while (platesListIterator.hasPrevious())  String plate = platesListIterator.previous(); System.out.println(plate); > > >

# Output === Iterate over a Stack using Java 8 forEach() method === Plate 1 Plate 2 Plate 3 Plate 4 === Iterate over a Stack using iterator() === Plate 1 Plate 2 Plate 3 Plate 4 === Iterate over a Stack using iterator() and Java 8 forEachRemaining() method === Plate 1 Plate 2 Plate 3 Plate 4 === Iterate over a Stack from TOP to BOTTOM using listIterator() === Plate 4 Plate 3 Plate 2 Plate 1

In this article, you learned what is a Stack, how to create a Stack in Java, how to perform push and pop operations in a Stack, how to check if the Stack is empty, how to find the size of the Stack and how to search for an element in the Stack.

Thanks for reading. See you in the next post.

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