Java Stack Class in Collection Framework, Essays (university) of Java Programming

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THE COLLECTIONS

FRAMEWORK

Sagar B V 4AL18CS

STACK

• Java Collection framework provides a Stack class which models and implements Stack data structure.
• The class is based on the basic principle of last-in-first-out.
• Stack only defines the default constructor, which creates an empty stack.
• Syntax: class Stack Here, E specifies the type of element stored in the stack.
  • To put an object on the top of the stack, call push().
  • To remove and return the top element, call pop().
  • An EmptyStackException is thrown if you call pop() when the invoking stack is empty.

Here is an example that creates a stack, pushes several integer objects onto it, and then pops them off again: // Demonstrate the stack class. import java.util.*; class StackDemo { static void showpush(stack st, int a) { st.push(a); System.out.println(“push(“ + a + “)”); System.out.println(“stack: “ +st); }

Static void showpop(stack st) { System.out.print(“pop->“); Integer a = (Integer) st.pop(); System.out.println(a); System.out.println(“stack: “ +st); } static void showpeek(Stack st) { Integer element = (Integer) st.peek(); System.out.println("Element on stack top : " + element); }

public static void main(String args[]) { stack st = new Stack(); showpush(st, 42); showpush(st, 66); showpush(st, 99); showpop(st); showpeek (st); showsearch (st,66); showsearch (st,15); } try{ Integer obj = (Integer)st.pop(); } catch (EmptyStackException e) { System.out.println(“Empty stack"); } }

The following produce the output produced by the program: push(42) stack: [42] push(66) stack: [42,66] push(99) stack: [42,66,99] pop -> 99 stack: [42,66] Element on stack top : Element is found at position 2 Element not found