This is what i have and i cannot figure out why it wont work. It says that the D

Question

This is what i have and i cannot figure out why it wont work. It says that the DequeApp class wont compile due to it not being able to find the DataInputStream symbol. If you could help me get this running that would be great!

import java.io.*;
class Node
{
public int data;
public Node next;
public Node previous;
public Node(int x)
{
data=x;
}
public void displayNode()
{
System.out.print(data+" ");
}
}
class DoublyLinkList
{
private Node first;
private Node last;
public DoublyLinkList()
{
first=null;
last=null;
}
public void insertFirst(int x)
{
Node newNode=new Node(x);
newNode.next=null;
if(isEmpty())
last=newNode;
else
first.previous=newNode;
newNode.next=first;
first=newNode;
}
public void insertLast(int x)
{
Node newNode=new Node(x);
newNode.next=null;
if(isEmpty())
first=newNode;
else
{
last.next=newNode;
newNode.previous=last;
}
last=newNode;
}
public int deleteFirst()
{
int t=first.data;
if(first.next==null)
last=null;
else
first.next.previous=null;
first=first.next;
return t;
}
public int deleteLast()
{
int t=last.data;
if(first.next==null)
first=null;
else
last.previous.next=null;
last=last.previous;
return t;
}
public boolean isEmpty()
{
return(first==null);
}
public void displayForward()
{
Node current=first;
while(current!=null)
{
current.displayNode();
current=current.next;
}
}
public void displayBackward()
{
Node current=last;
while(current!=null)
{
current.displayNode();
current=current.previous;
}
}
}
class Deque
{
private DoublyLinkList l;
public Deque()
{
l=new DoublyLinkList();
}
public void insertLeft(int x)
{
l.insertFirst(x);
System.out.print("Inserted to Front ");
}
public void insertRight(int x)
{
l.insertLast(x);
System.out.print("Inserted to Rear ");
}
public int deleteLeft()
{
return l.deleteFirst();
}
public int deleteRight()
{
return l.deleteLast();
}
public boolean isQueueEmpty()
{
return l.isEmpty();
}
public void displayFromFront()
{
l.displayForward();
}
public void displayFromRear()
{
l.displayBackward();
}
}
class DequeApp
{
public static void main(String args[])throws IOException
{
String ch="y";
DataInputStream inp=new DataInputStream(System.in);
int n,d;
Deque q=new Deque();
while(ch.equals("y"))
{
System.out.println("MENU");
System.out.println("--------");
System.out.println("1.Insert at Front");
System.out.println("2.Insert at Rear");
System.out.println("3.Delete at Front");
System.out.println("4.Delete at Rear");
System.out.println("5.Display From Front");
System.out.println("6.Display From Rear");
System.out.println("Enter your choice ");
n=Integer.parseInt(inp.readLine());
switch(n)
{
case 1: System.out.println("Enter the data ");
d=Integer.parseInt(inp.readLine());
q.insertLeft(d);
break;
case 2: System.out.println("Enter the data ");
d=Integer.parseInt(inp.readLine());
q.insertRight(d);
break;
case 3: if(q.isQueueEmpty())
System.out.print("Deque is Empty ");
else
{
d=q.deleteLeft();
System.out.print("Deleted data:- "+d);
}
break;
case 4: if(q.isQueueEmpty())
System.out.print("Deque is Empty ");
else
{
d=q.deleteRight();
System.out.print("Deleted data:- "+d);
}
break;
case 5: if(q.isQueueEmpty())
System.out.print("Deque is Empty ");
else
{
System.out.print("Datas in Deque From Front:- ");
q.displayFromFront();
}
break;
case 6: if(q.isQueueEmpty())
System.out.print("Deque is Empty ");
else
{
System.out.print("Datas in Deque From Rear:- ");
q.displayFromRear();
}
break;
default: System.out.print("Invalid choice ");
}
System.out.println("");
System.out.print("Enter y to continue ");
ch=inp.readLine();
}
}
}

Explanation / Answer

Add these statements at the beginning of the deque class

import java.io.DataInputStream;
import java.io.IOException;

You should import the io package to access any classes in it.

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