Stack DS

 /* 

Classes and objects

Stack data structures 

*/

import java.io.*;

import java.util.*;

class StkDS

{

int tos, capacity;

int [] Stk;

public StkDS(int c)

{

tos = -1;

capacity = c;

Stk = new int[capacity];

}

int size()

{

return tos+1;

}

boolean isFull()

{

return((tos+1) == capacity);

}

boolean isEmpty()

{

return (tos==-1);

}

void push(int x)

{

if(!isFull())

Stk[++tos]=x;

else

System.out.print("\nFull stack. Cant insert element.");

}

void pop()

{

if(!isEmpty())

tos--;

else

System.out.print("\nEmpty stack. Cant delete element.");

}

int topandpop()

{

if(!isEmpty())

return(Stk[tos--]);

else

{

System.out.print("\nEmpty stack. Cant delete element.");

return -1;

}

}

void peek()

{

if(!isEmpty())

System.out.print("\nElement on top of stack is "+Stk[tos]); 

else

System.out.print("\nEmpty stack. No element present.");

}

void fnDisplay()

{

if(!isEmpty())

{

System.out.print("\nElements in stack : ");

for(int i=0;i<=tos;i++)

System.out.print(Stk[i]+" ");

}

else

System.out.println("\nEmpty stack. No elements present. ");

}

}

class StackDS

{

public static void main(String []as)throws IOException

{

Scanner sc = new Scanner(System.in);

System.out.print("\nEnter stack size : ");

int cap = sc.nextInt();

StkDS s = new StkDS(cap);

int choice;

do

{

System.out.print("\nMenu: 1. Push\t2. Pop\t3. TopandPop\t4. Peek\t5. Exit");

System.out.print("\nEnter choice : ");

choice = sc.nextInt();

switch(choice)

{

case 1: System.out.print("\nEnter element : ");

int ele=sc.nextInt();

s.push(ele);

s.fnDisplay();break;

case 2: s.pop();s.fnDisplay();break;

case 3: int val=s.topandpop();

System.out.println("\nDeleted element : "+val);

s.fnDisplay();break;

case 4: s.peek();s.fnDisplay();break;

case 5: System.exit(0);

}

}while(true);

}

}