Define linked list (linked list)

  Definition int Type linked list

public class ListNode {
    int val; // data ： Node data 
    ListNode next; // object ： Reference the next node object ,

    // Add construction method 
    ListNode(int val){// Construction method ： The construction method is the same as the class name 
        this.val = val; // Assign the received parameter to the current class val Variable 
    }
}

Define generic linked list

public class ListNode<E> {
    E val; // data ： Node data 
    ListNode next; // object ： Reference the next node object ,

    // Add construction method 
    ListNode(E val){// Construction method ： The construction method is the same as the class name 
        this.val = val; // Assign the received parameter to the current class val Variable 
    }
}

Create linked lists and traverse linked lists

static class Test_{
        // Static declarations are not allowed in inner classes 
        public static void main(String[] args) {
            // Create the first node 
            ListNode nodeSta = new ListNode(0);
            // Declare a variable to point to the current node during the move 
            ListNode nextNode;
            // Point to the head node 
            nextNode = nodeSta;

            // Create a linked list ( The length is 10)
            for (int i = 1; i <10 ; i++) {
                // Generate new nodes 
                ListNode node = new ListNode(i);
                // Connect the new node 
                nextNode.next = node;
                // Move the current node back 
                nextNode = nextNode.next;
            }// When the cycle is complete ,nextNode Point to the last node 
            // Reassign the value so that the mobile node points to the first node 
            nextNode = nodeSta;
            // Printout 
            print(nextNode);
        }
        static void print(ListNode listNode){
            // Create a linked list node 
            while (listNode!=null){
                if(listNode.next==null){
                    System.out.print(listNode.val);
                }else {
                    System.out.print(listNode.val + "->");
                }
                listNode = listNode.next;
            }
        }
    }

  Output results ：0->1->2->3->4->5->6->7->8->9

Insert the list

// Insert node 
            while(nextNode!=null){
                // This is because of the linked list defined by the model used before , Therefore, it is necessary to specify val The data type of is int
                if((int)nextNode.val==5){
                    ListNode newnode = new ListNode(99);
                    // Save the next node 
                    ListNode node = nextNode.next;
                    // Insert new node 
                    nextNode.next = newnode;
                    // The next node of the new node points to the previously saved node 
                    newnode.next = node;
                }
                nextNode=nextNode.next;
            }// After the cycle ,nextNode Point to the first node 
            nextNode =nodeSta;
            print(nextNode);
        }
        // Printout 
        static void print(ListNode listNode){
            // Create a linked list node 
            while (listNode!=null){
                if(listNode.next==null){
                    System.out.print(listNode.val);
                }else {
                    System.out.print(listNode.val + "->");
                }
                listNode = listNode.next;
            }
        }

Output results ： 0->1->2->3->4->5->99->6->7->8->9

Replacement node

// Replacement node 
            while(nextNode!=null){
                if ((int)nextNode.val==4){
                    // Generate new nodes 
                    ListNode newnode = new ListNode(98);
                    // Save the next node of the replacement node 
                    ListNode node = nextNode.next.next;
                    // Point the replacement node to null, Waiting for garbage collection 
                    nextNode.next.next = null;
                    // Point the current node to the new node 
                    nextNode.next = newnode;
                    // Point the node to the next node of the original replacement node 
                    newnode.next = node;
                }
                // Move current node 
                nextNode = nextNode.next;
            }

  Output results ：0->1->2->3->4->98->99->6->7->8->9

Delete node

// Delete node 
            while(nextNode!=null){
                if ((int)nextNode.val==3){
                    // Keep the pointing node of the next node of the current node 
                    ListNode node = nextNode.next.next;
                    // Point the next node of the current node to null, Waiting for garbage collection 
                    nextNode.next.next = null;
                    // Point the current node to the reserved node 
                    nextNode.next = node;
                }
                // The mobile node moves backward 
                nextNode = nextNode.next;
            }

Output results ：0->1->2->3->98->99->6->7->8->9