用java实现单链表和单链表的增、删、改、插

入、查找等操作，可以参考以下代码实现：

单链表的节点类：

public class ListNode {
    int val;
    ListNode next;
    ListNode(int x) { val = x; }
}

单链表类：

public class LinkedList {
    private ListNode head;

    public LinkedList() {
        head = null;
    }

    // 增加节点
    public void addNode(int val) {
        ListNode newNode = new ListNode(val);
        if (head == null) {
            head = newNode;
        } else {
            ListNode cur = head;
            while (cur.next != null) {
                cur = cur.next;
            }
            cur.next = newNode;
        }
    }

    // 删除节点
    public void deleteNode(int val) {
        if (head == null) {
            return;
        }
        if (head.val == val) {
            head = head.next;
            return;
        }
        ListNode cur = head;
        while (cur.next != null) {
            if (cur.next.val == val) {
                cur.next = cur.next.next;
                return;
            }
            cur = cur.next;
        }
    }

    // 修改节点
    public void modifyNode(int oldVal, int newVal) {
        ListNode cur = head;
        while (cur != null) {
            if (cur.val == oldVal) {
                cur.val = newVal;
                return;
            }
            cur = cur.next;
        }
    }

    // 插入节点
    public void insertNode(int pos, int val) {
        ListNode newNode = new ListNode(val);
        if (pos == 0) {
            newNode.next = head;
            head = newNode;
            return;
        }
        ListNode cur = head;
        for (int i = 0; i < pos - 1 && cur != null; i++) {
            cur = cur.next;
        }
        if (cur == null) {
            return;
        }
        newNode.next = cur.next;
        cur.next = newNode;
    }

    // 查找节点
    public boolean searchNode(int val) {
        ListNode cur = head;
        while (cur != null) {
            if (cur.val == val) {
                return true;
            }
            cur = cur.next;
        }
        return false;
    }

    // 打印链表
    public void printList() {
        ListNode cur = head;
        while (cur != null) {
            System.out.print(cur.val + " ");
            cur = cur.next;
        }
        System.out.println();
    }
}

使用示例：

public static void main(String[] args) {
    LinkedList list = new LinkedList();
    list.addNode(1);
    list.addNode(2);
    list.addNode(3);
    list.printList(); // 输出：1 2 3
    list.deleteNode(2);
    list.printList(); // 输出：1 3
    list.modifyNode(1, 4);
    list.printList(); // 输出：4 3
    list.insertNode(1, 2);
    list.printList(); // 输出：4 2 3
    System.out.println(list.searchNode(2)); // 输出：true
    System.out.println(list.searchNode(5)); // 输出：false
}