Implementation of Stack in Java

A stack is an abstract data type that serves as a collection of elements, with two principal operations:

  1. push adds an element to the collection
  2. pop removes the last element that was added.

It is a LIFO (Last In First Out) kind of data structure. That means the element which added at last will be taken out first.

import java.io.*;
class stack
{
int size;
int item[];
int top;

public stack()
{
size=10;
item= new int[size];
top=-1;
}
public void push(int ele)
{
if (top==(size-1))
{
System.out.println(“Stack Overflow”);
}
else
{
top++;
item[top]=ele;
}
}
public int pop()
{
if (top==-1)
{
System.out.println(“No Elements”);
return(-1);
}
else
{
int x=item[top];
top–;
return(x);
}
}
public int peek()
{
if (top==-1)
{
System.out.println(“No Elements”);
return(-1);
}
else
return(item[top]);
}
public void display()
{
System.out.println();
if (top==-1)
{
System.out.println(“No Elements”);
}
else
{
System.out.println(“Stack is”);
for(int i=0;i<=top;i++) System.out.println(item[i]); } } } class stackank { public static void main(String args[]) throws IOException { BufferedReader obj=new BufferedReader(new InputStreamReader(System.in)); stack s=new stack(); int e,ch; do { System.out.println(); System.out.println("Stack Implementation"); System.out.println("1.Add Element to Stack"); System.out.println("2.Remove Element From Stack"); System.out.println("3.Peek"); System.out.println("4.Display Stack"); System.out.println("5.Exit"); System.out.println("Select Option"); ch=Integer.parseInt(obj.readLine()); switch (ch) { case 1: { System.out.println("Enter Number to Push"); e=Integer.parseInt(obj.readLine()); s.push(e); break; } case 2: { System.out.println("Poped Element is"+s.pop()); break; } case 3: { System.out.println("On Implementing peek the result is "+s.peek()); break; } case 4: { s.display(); break; } case 5: { break; } } }while (ch!=5); } } /* Stack Implementation 1.Add Element to Stack 2.Remove Element From Stack 3.Peek 4.Display Stack 5.Exit Select Option 1 Enter Number to Push 10 Stack Implementation 1.Add Element to Stack 2.Remove Element From Stack 3.Peek 4.Display Stack 5.Exit Select Option 4 Stack is 10 Stack Implementation 1.Add Element to Stack 2.Remove Element From Stack 3.Peek 4.Display Stack 5.Exit Select Option 1 Enter Number to Push 20 Stack Implementation 1.Add Element to Stack 2.Remove Element From Stack 3.Peek 4.Display Stack 5.Exit Select Option 4 Stack is 10 20 Stack Implementation 1.Add Element to Stack 2.Remove Element From Stack 3.Peek 4.Display Stack 5.Exit Select Option 1 Enter Number to Push 30 Stack Implementation 1.Add Element to Stack 2.Remove Element From Stack 3.Peek 4.Display Stack 5.Exit Select Option 4 Stack is 10 20 30 Stack Implementation 1.Add Element to Stack 2.Remove Element From Stack 3.Peek 4.Display Stack 5.Exit Select Option 3 O n Implementing peek the result is 30 Stack Implementation 1.Add Element to Stack 2.Remove Element From Stack 3.Peek 4.Display Stack 5.Exit Select Option 2 Poped Element is30 Stack Implementation 1.Add Element to Stack 2.Remove Element From Stack 3.Peek 4.Display Stack 5.Exit Select Option 4 Stack is 10 20 Stack Implementation 1.Add Element to Stack 2.Remove Element From Stack 3.Peek 4.Display Stack 5.Exit Select Option 5 Process Exit... */ [/java]

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