PROGRAM TO IMPLEMENT LINKED LIST

Implementation File:

import java.io.*;

class node /*Class to create a node like structure*/
{
int data;
Object nxt;
}

class linkedlist /*Class that contain the set functions for implementation*/
{
node head;
linkedlist()
{
head=new node();
}

public void insertfirst() throws IOException
/*Function to insert a element in the begining*/
{
try
{
int i;
String s1;
node newnode=new node();
System.out.println("Input your data for your node");
BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
s1=br.readLine();
i=Integer.parseInt(s1);
newnode.data=i;
newnode.nxt=head.nxt;
head.nxt=newnode;
System.out.print("Your node ");
System.out.print(newnode.data);
System.out.println(" is inserted at first");
}
catch(Exception e)
{
System.out.println("Error check ur input");
}
}






public void insertlast() /*To insert an element in the last*/
{
try
{
node temp;
temp=head;
node newnode=new node();
int i;
String s1;
System.out.println("Input your data for your node");
BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
s1=br.readLine();
i=Integer.parseInt(s1);
newnode.data=i;
while(temp.nxt!=null)
{
temp=(node)temp.nxt;
}
temp.nxt=newnode;
System.out.print("Your node ");
System.out.print(newnode.data);
System.out.println(" is inserted at last.");
}

catch(Exception e)
{
System.out.println(" Error check ur input");

}

}

public void insertafter() /*To insert an element after the specified one*/
{
try
{
int i,j;
String s1;
node newnode;
node temp;
System.out.println("Input your data for your node");
BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
s1=br.readLine();
i=Integer.parseInt(s1);
temp=head;
newnode=new node();
newnode.data=i;
System.out.println("Input the data after which your node is to b inserted");


BufferedReader b=new BufferedReader(new InputStreamReader(System.in));
s1=b.readLine();
j=Integer.parseInt(s1);
while(temp.nxt!=null)
{
if(temp.data==j)
{
newnode.nxt=temp.nxt;
temp.nxt=newnode;
System.out.print("Your node ");
System.out.print(newnode.data);
System.out.print(" is inserted after ");
System.out.println(temp.data);
break;
}
else
{
temp=(node)temp.nxt;
}
}
if(temp.data!=j)
{
System.out.println("Please enter a data present in the list");
}

}
catch(Exception e)
{
System.out.println("Error check ur input");
}
}
public void deletefirst() /*To delete the first element in the list*/
{
if(head.nxt==null)
{
System.out.println("The list is empty so insert data herafter before further deletion.");
}
else
{
node current;
current=head;
current=(node)current.nxt;
head=current;
System.out.print("The node ");
System.out.print(current.data);
System.out.println(" is deleted.");
}
}



public void deletelast() /*To delete the last element*/
{
if(head.nxt==null)
{
System.out.println("The list is empty so insert data herafter before further deletion.");
}

else
{
node current;
current=head;
node previous=new node();
while(current.nxt!=null)
{
previous=current; //during lastnode last but one will be stored in previous
current=(node)current.nxt; //last node is stored in current
}
previous.nxt=null; //last but one's pointer is made to null thus leaving lastnode
System.out.print("The node ");
System.out.print(current.data);
System.out.println(" is deleted.");
}
}

public void deleteafter() /*To delete the element after the one specified*/
{
try
{
String s1;
if(head.nxt==null)
{
System.out.println("The list is empty so insert data herafter before further deletion.");
}
else
{
int j;
node deleted;
node current;
current=head;
System.out.println("Input the data after which your node is to be deleted");
BufferedReader b=new BufferedReader(new InputStreamReader(System.in));
s1=b.readLine();
j=Integer.parseInt(s1);
while(current.nxt!=null)
{
if(current.data==j)
{
deleted=(node)current.nxt; //link of the given data's node is placed in deleted
current.nxt=deleted.nxt; //link of the given data's node is made to point to the link of the node to be deleted
System.out.print("The node ");
System.out.print(deleted.data);
System.out.println(" is deleted");
break;
}
else {
current=(node)current.nxt;
}
}
System.out.println("Please enter a data present in the list");
}
}
catch(Exception e) {
System.out.println("Error check ur input");
}
}
public void display() /*To display the list of elements*/
{
node temp;
if (head.nxt==null)
{
System.out.println("Your list is empty so insert data ");
}
else
{
System.out.println("The list of elements are");
temp=head;
while(temp.nxt!=null)
{
temp =(node) temp.nxt;
System.out.println(temp.data);
}
}
}
}













Application File:
=============

import java.io.*;
//import linkedlist.*;


class llist
{
public static void main(String args[])
{
try
{
linkedlist f=new linkedlist();
String c;
char d;
int j=0;
do
{
System.out.println("Choice 1-Insert First");
System.out.println("Choice 2-Insert Last");
System.out.println("Choice 3-Delete First");
System.out.println("Choice 4-Delete Last");
System.out.println("Choice 5-Insert After");
System.out.println("Choice 6-Delete After");
System.out.println("Choice 7-Display");
System.out.println("Choose ur choice between 1 and 7");
BufferedReader bf=new BufferedReader(new InputStreamReader(System.in));
int flag=0;
while(flag==0)
{
c=bf.readLine();
try
{
j=Integer.parseInt(c);
flag=1;
}
catch(NumberFormatException e)
{
System.out.println("Incorrect input");
System.out.println("Choice 1-Insert First");
System.out.println("Choice 2-Insert Last");
System.out.println("Choice 3-Delete First");
System.out.println("Choice 4-Delete Last");
System.out.println("Choice 5-Insert After");
System.out.println("Choice 6-Delete After");
System.out.println("Choice 7-Display");
System.out.println("Choose ur choice between 1 and 7");
}
}
switch(j)
{
case 1:
f.insertfirst();
f.display();
break;
case 2:
f.insertlast();
f.display();
break;
case 3:
f.deletefirst();
f.display();
break;
case 4:
f.deletelast();
f.display();
break;
case 5:
System.out.println("Enter a element present in the list");
f.display();
f.insertafter();
f.display();
break;
case 6:
System.out.println("Enter a element present in the list");
f.display();
f.deleteafter();
f.display();
break;
case 7:
f.display();
break;
default:
System.out.println("Enter a choice between 1 and 7"); break;
}
System.out.println("do u want to continue");
BufferedReader bf1=new BufferedReader(new InputSreamReader(System.in));
d=(char)bf1.read();
}while(d=='y');
}
catch(Exception e)
{
System.out.println("Invalid input");
return;
}
}
}



Output:


c:\jdk1.4\bin\Linkedlist>javac linkedlist.java

c:\jdk1.4\bin\Linkedlist>javac llist.java

c:\jdk1.4\bin\Linkedlist>java llist

Choice 1-Insert First
Choice 2-Insert Last
Choice 3-Delete First
Choice 4-Delete Last
Choice 5-Insert After
Choice 6-Delete After
Choice 7-Display
Choose ur choice between 1 and 7
1
Input your data for your node
5
Your node 5 is inserted at first
The list of elements are
5

do u want to continue
y
Choice 1-Insert First
Choice 2-Insert Last
Choice 3-Delete First
Choice 4-Delete Last
Choice 5-Insert After
Choice 6-Delete After
Choice 7-Display
Choose ur choice between 1 and 7
2
Input your data for your node
8
Your node 8 is inserted at last.
The list of elements are
5
8

do u want to continue
y
Choice 1-Insert First
Choice 2-Insert Last
Choice 3-Delete First
Choice 4-Delete Last
Choice 5-Insert After
Choice 6-Delete After
Choice 7-Display
Choose ur choice between 1 and 7
2
Input your data for your node
9
Your node 9 is inserted at last.
The list of elements are
5
8
9

do u want to continue
y
Choice 1-Insert First
Choice 2-Insert Last
Choice 3-Delete First
Choice 4-Delete Last
Choice 5-Insert After
Choice 6-Delete After
Choice 7-Display
Choose ur choice between 1 and 7
5
Enter a element present in the list
The list of elements are
5
8
9
Input your data for your node
6
Input the data after which your node is to b inserted
5
Your node 6 is inserted after 5
The list of elements are
5
6
8
9

do u want to continue
y
Choice 1-Insert First
Choice 2-Insert Last
Choice 3-Delete First
Choice 4-Delete Last
Choice 5-Insert After
Choice 6-Delete After
Choice 7-Display
Choose ur choice between 1 and 7
3
The node 5 is deleted.
The list of elements are
6
8
9

do u want to continue
y
Choice 1-Insert First
Choice 2-Insert Last
Choice 3-Delete First
Choice 4-Delete Last
Choice 5-Insert After
Choice 6-Delete After
Choice 7-Display
Choose ur choice between 1 and 7
4
The node 9 is deleted.
The list of elements are
6
8

do u want to continue
y
Choice 1-Insert First
Choice 2-Insert Last
Choice 3-Delete First
Choice 4-Delete Last
Choice 5-Insert After
Choice 6-Delete After
Choice 7-Display
Choose ur choice between 1 and 7
4
The node 8 is deleted.
The list of elements are
6

do u want to continue?
n

c:\jdk1.4\bin\Linkedlist>