Question

Write a java program implementing the Linked list.

It should be on an small office who has 5 employees. The program ask the user for ID, First name, Last name and what field the work in(eg: accounting, programmer, HR etc). Each employee (with all the information of that paticular employee) should be placed in one node in the program. The program should repeat and ask the user for all 5 employees information. Also when you display the Linked list it should be sorted by increasing order of the Employee ID. Employee Id should be the primary key . The program should also be able to delete an employee by their ID number. It should have an menu to ask the user for the following options:

1. To add an new employee
2. To delete an employee
3. To search an employee
4. To display list of employee

Whole program is based on linked list and should be sorted.

Answer 1

import java.util.Scanner;

class ListNode{
   int ID;
   String fname;
   String lname;
   String fwork;
   ListNode next;
  
   public ListNode(int id,String name,String lname,String work){
       this.ID=id;
       this.fname=name;
       this.lname=lname;
       this.fwork=work;
   }
}

public class Employee {
   ListNode head;
   ListNode sorted;
  
   void push(int id,String name,String lname,String work){
       ListNode newnode=new ListNode(id,name,lname,work);
       newnode.next=head;
       head=newnode;
   }
  
   //..........utility function to sort the list............
void insertionSort(ListNode headref){
   sorted=null;
   ListNode current=headref;
  
   //pick node 1 by 1 and create a soted list ....
   while(current!=null){
       ListNode next=current.next;
       sortedInsert(current);
       current=next;
   }
   //assign the sorted list to orignal head node
   head=sorted;
}   
  
void sortedInsert(ListNode newnode){
   if(sorted==null||sorted.ID>=newnode.ID){
       newnode.next=sorted;
       sorted=newnode;
   }else{
       ListNode current=sorted;
       while (current.next != null && current.next.ID < newnode.ID)
{
current = current.next;
}
newnode.next = current.next;
current.next = newnode;
   }
}
  
//..................utility ends.......................
  
   void printlist(ListNode head)
{
       ListNode temp=head;
      
       if(temp==null){
           System.out.println("List is empty");
       }
while (temp != null)
{
System.out.println("Name:"+temp.fname +" "+temp.lname+"ID:"+temp.ID+" Work:"+temp.fwork);
temp = temp.next;
}
}
  
   void delete(int id){
       //variable to hold node to be deleted and previous node..
       ListNode temp=head,prec=null;
      
       //if node to be delted is first node itself
       if(temp!=null && temp.ID==id){
           head=temp.next;
           return;
       }
      
       //traverse through the list to find node to be deleted
       while(temp!=null && temp.ID!=id){
           prec=temp;
           temp=temp.next;
       }
      
       if(temp==null){
       System.out.println("Employee is not present in the list..");
           return;
       }
       prec.next=temp.next;
      
      
   }

  
  
public static void main(String[] args){
  
   Employee list=new Employee();
   int temp_NumOfEmployeesToEnter=5;
  
   while(true){
   System.out.println("1.To add an new employee\n"+
           "2.To delete an employee\n"+
           "3.To search an employee\n"+
           "4.To display list of employee\n");
   Scanner sc=new Scanner(System.in);
   int temp=sc.nextInt();
   switch(temp){
   case 1:
       System.out.println("Enter ID:");
       int id=sc.nextInt();
       System.out.println("Enter first name:");
       Scanner scc=new Scanner(System.in);
       String fname=scc.nextLine();
       System.out.println("Enter last name:");
       String lname=scc.nextLine();
       System.out.println("Enter workProfile:(eg: accounting, programmer, HR etc)");
       String work=scc.nextLine();
      
       list.push(id, fname, lname, work);
       temp_NumOfEmployeesToEnter--;
       if(temp_NumOfEmployeesToEnter<=0){
           continue;
       }else{
           System.out.println("optional-Enter information for "+temp_NumOfEmployeesToEnter+ " more employees");
       }
  
       break;
  
   case 2:
       System.out.println("Enter the employee ID to be deleted");
   id=sc.nextInt();
       list.delete(id);
   break;
  
   case 3:
       System.out.println("Enter the employee ID to be searched");
       int x=sc.nextInt();
      
       ListNode current =list.head;
   boolean temp_var=true;
   //traverse list to find the employee...
       while(current!=null){
           if(current.ID==x){
               System.out.println("Name:"+current.fname +" "+current.lname+"ID:"+current.ID+" Work:"+current.fwork);
           temp_var=false;
           }
           current=current.next;
       }
       if(temp_var){
       System.out.println("Employee with ID "+x+" does not exits");
       }
   break;
  
   case 4:
       list.insertionSort(list.head); //sorting list and printing..
       list.printlist(list.head);
       break;
   default:
       System.out.println("Pleas enter valid response");
   }
   }
  
   }

}

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