public class LinkedList { 
   private class Data{ 
     private Object obj; 
     private Data next = null;       
     Data(Object obj){ 
       this.obj = obj; 
     } 
   } 
   private Data first = null; 
    
   public void insertFirst(Object obj){ 
     Data data = new Data(obj); 
     data.next = first; 
     first = data; 
   } 
   public Object deleteFirst() throws Exception{ 
     if(first == null) 
       throw new Exception("empty!"); 
     Data temp = first; 
     first = first.next; 
     return temp.obj; 
   }     
   public Object find(Object obj) throws Exception{ 
     if(first == null) 
       throw new Exception("LinkedList is empty!"); 
     Data cur = first; 
     while(cur != null){ 
       if(cur.obj.equals(obj)){ 
         return cur.obj; 
       } 
       cur = cur.next; 
     } 
     return null; 
   } 
   public void remove(Object obj) throws Exception{ 
     if(first == null) 
       throw new Exception("LinkedList is empty!"); 
     if(first.obj.equals(obj)){ 
       first = first.next; 
     }else{ 
       Data pre = first; 
       Data cur = first.next; 
       while(cur != null){ 
         if(cur.obj.equals(obj)){ 
           pre.next = cur.next; 
         } 
        pre = cur; 
         cur = cur.next; 
       } 
     } 
   } 
   public boolean isEmpty(){ 
     return (first == null); 
   } 
   public void display(){ 
     if(first == null) 
       System.out.println("empty"); 
     Data cur = first; 
     while(cur != null){ 
       System.out.print(cur.obj.toString() + " -> "); 
       cur = cur.next; 
     } 
     System.out.print("\n"); 
   }     
   public static void main(String[] args) throws Exception { 
     LinkedList ll = new LinkedList(); 
     ll.insertFirst(4); 
     ll.insertFirst(3); 
     ll.insertFirst(2); 
     ll.insertFirst(1); 
     ll.display(); 
     ll.deleteFirst(); 
     ll.display(); 
     ll.remove(3); 
     ll.display(); 
     System.out.println(ll.find(1)); 
     System.out.println(ll.find(4)); 
   } 
 } 

 1 -> 2 -> 3 -> 4 ->  
 2 -> 3 -> 4 ->  
 2 -> 4 ->  
 null 
 4 

 public class FirstLastList { 
   private class Data{ 
     private Object obj; 
     private Data next = null;       
     Data(Object obj){ 
       this.obj = obj; 
     } 
   }     
   private Data first = null; 
   private Data last = null;     
   public void insertFirst(Object obj){ 
     Data data = new Data(obj); 
     if(first == null) 
       last = data; 
     data.next = first; 
     first = data; 
   }     
   public void insertLast(Object obj){ 
     Data data = new Data(obj); 
     if(first == null){ 
       first = data; 
     }else{ 
       last.next = data;   
     } 
     last = data; 
   }     
   public Object deleteFirst() throws Exception{ 
      if(first == null) 
       throw new Exception("empty"); 
      Data temp = first; 
      if(first.next == null) 
       last = null; 
      first = first.next; 
      return temp.obj; 
  }   
   public void deleteLast() throws Exception{ 
     if(first == null) 
       throw new Exception("empty"); 
     if(first.next == null){ 
       first = null; 
       last = null; 
     }else{ 
       Data temp = first; 
       while(temp.next != null){ 
         if(temp.next == last){ 
           last = temp; 
           last.next = null; 
           break; 
        } 
        temp = temp.next; 
      } 
     } 
   } 
   public void display(){ 
     if(first == null) 
       System.out.println("empty"); 
     Data cur = first; 
     while(cur != null){ 
       System.out.print(cur.obj.toString() + " -> "); 
       cur = cur.next; 
     } 
     System.out.print("\n"); 
   } 
   public static void main(String[] args) throws Exception { 
     FirstLastList fll = new FirstLastList(); 
     fll.insertFirst(2); 
     fll.insertFirst(1); 
     fll.display(); 
     fll.insertLast(3); 
     fll.display(); 
     fll.deleteFirst(); 
     fll.display(); 
     fll.deleteLast(); 
     fll.display(); 
   } 
 } 

 1 -> 2 ->  
 1 -> 2 -> 3 ->  
 2 -> 3 ->  
 2 -> 

public class SortedList { 
   private class Data{ 
     private Object obj; 
     private Data next = null;       
     Data(Object obj){ 
       this.obj = obj; 
     } 
   }   
   private Data first = null;     
   public void insert(Object obj){ 
     Data data = new Data(obj); 
     Data pre = null; 
     Data cur = first; 
     while(cur != null && (Integer.valueOf(data.obj.toString()) 
        .intValue() > Integer.valueOf(cur.obj.toString()) 
         .intValue())){ 
       pre = cur; 
      cur = cur.next; 
     } 
     if(pre == null) 
       first = data; 
     else 
       pre.next = data; 
     data.next = cur; 
   }     
   public Object deleteFirst() throws Exception{ 
     if(first == null) 
       throw new Exception("empty!"); 
     Data temp = first; 
     first = first.next; 
     return temp.obj; 
   }     
   public void display(){ 
     if(first == null) 
       System.out.println("empty"); 
     System.out.print("first -> last : "); 
     Data cur = first; 
     while(cur != null){ 
       System.out.print(cur.obj.toString() + " -> "); 
       cur = cur.next; 
     } 
     System.out.print("\n"); 
   }     
   public static void main(String[] args) throws Exception{ 
     SortedList sl = new SortedList(); 
     sl.insert(80); 
     sl.insert(2); 
     sl.insert(100); 
     sl.display(); 
     System.out.println(sl.deleteFirst()); 
     sl.insert(33); 
     sl.display(); 
     sl.insert(99); 
     sl.display(); 
   } 
 } 

 first -> last : 2 -> 80 -> 100 ->  
 2 
 first -> last : 33 -> 80 -> 100 ->  
 first -> last : 33 -> 80 -> 99 -> 100 ->