public class MyLinkedList {

    static class Address {
        public int val;
        public Address address;

        public Address(int val) {
            this.val = val;
        }
    }

    public Address head;

    public void createLinked() {
        Address node1 = new Address(12);
        Address node2 = new Address(23);
        Address node3 = new Address(34);
        Address node4 = new Address(45);
        Address node5 = new Address(56);
        node1.address = node2;
        node2.address = node3;
        node3.address = node4;
        node4.address = node5;
        this.head = node1;
    }

    public void addFirst(int data) { //头插法
        Address node = new Address(data);
        node.next = head;
        head = node;
    }

    public void addLast(int data) { //尾插法
        Address node = new Address(data);
        Address cur = head;
        if (head == null) {
            head = node;
            return;
        }
        while (cur.next != null) {
            cur = cur.next;
        }
        cur.next = node;
    }

    public void addIndex(int index, int data) { // 任意位置插⼊,第⼀个数据节点为0号下标
        int size = size();
        int count = 1;
        if (index < 0 || index > size) {
            return;
        }
        if (index == 0) {
            addFirst(data);
            return;
        }
        if (index == size) {
            addLast(data);
            return;
        }
        Address node = new Address(data);
        Address cur = head;
        while (count != index) {
            cur = cur.next;
            count++;
        }
        node.next = cur.next;
        cur.next = node;
    }

    public boolean contains(int key) { // 找是否包含关键字 key是否在单链表当中
        Address cur = head;
        while (cur != null) {
            if (cur.val == key) {
                return true;
            }
        }
        return false;
    }

    public void remove(int key) { // 删除第⼀次出现关键字为 key的节点
        Address cur = head;
        if (head == null) { // 如果链表为空
            return;
        }
        if (cur.val == key) { // 如果第一个元素为
            head = cur.next;
            return;
        }
        while (cur.next != null) {
            if (cur.next.val == key) {
                break;
            }
            cur = cur.next;
        }
        if (cur.next != null) {
            cur.next = cur.next.next;
        }
    }

    public void removeAllKey(int key) { // 删除所有值为 key的节点
        if (head == null) {
            return;
        }
        Address prev = head;
        Address cur = head.next;
        while (cur != null) {
            if (cur.val == key) {
                prev.next = cur.next;
                cur = cur.next;
            } else {
                prev = prev.next;
                cur = cur.next;
            }
        }
        if (head.val == key) {
            head = head.next;
        }
    }

    public int size() { // 得到单链表的⻓度
        Address cur = head;
        int count = 0;
        while (cur != null) {
            count++;
            cur = cur.next;
        }
        return count;
    }

    public void clear() { // 清除单链表
        head = null;
    }

    public void display() { // 打印单链表
        Address cur = head;
        while (cur != null) {
            System.out.print(cur.val + " ");
            cur = cur.next;
        }
        System.out.println();
    }
}

public class MyLinkedList {

    static class ListNode {
        public int val;
        public ListNode prev;
        public ListNode next;

        public ListNode() {

        }

        public ListNode(int val) {
            this.val = val;
            this.prev = null;
            this.next = null;
        }

    }

    public ListNode head;
    public ListNode last;

    public void addFirst(int data) { // 头插法
        ListNode node = new ListNode(data);
        if (head == null) {
            head = node;
            last = node;
        } else {
            node.next = head;
            head.prev = node;
            head = node;
        }
    }

    public void addLast(int data) { // 尾插法
        ListNode node = new ListNode(data);
        if (head == null) {
            head = node;
            last = node;
        } else {
            last.next = node;
            node.prev = last;
            last = node;
        }
    }

    public void addIndex(int index, int data) { //任意位置插⼊,第⼀个数据节点为0号下标
        if (index < 0 || index > size()) {
            return;
        }
        if (index == 0) {
            addFirst(data);
            return;
        }
        if (index == size()) {
            addLast(data);
            return;
        }
        ListNode cur = head;
        ListNode node = new ListNode(data);
        int count = index;
        while (count-- != 0) {
            cur = cur.next;
        }
        node.next = cur;
        node.prev = cur.prev;
        cur.prev.next = node;
        cur.prev = node;
    }

    public boolean contains(int key) { // 查找是否包含关键字 key是否在单链表当中
        ListNode cur = head;
        while (cur != null) {
            if (cur.val == key) {
                return true;
            }
            cur = cur.next;
        }
        return false;
    }

    public void remove(int key) { // 删除第⼀次出现关键字为 key的节点
        ListNode cur = head;
        if (cur.val == key) { // 判断第一个
            head = head.next;
            return;
        }
        while (cur.next != null) { // 判断中间部分
            if (cur.val == key) {
                cur.prev.next = cur.next;
                cur.next.prev = cur.prev;
                return;
            }
            cur = cur.next;
        }
        if (cur.val == key) { // 判断最后一个
            cur.prev.next = null;
            last = last.prev;
        }
    }

    public void removeAllKey(int key) { // 删除所有值为 key的节点
        ListNode cur = head;
        while (cur != null) {
            if(cur.val == key) {
                if(cur == head) {
                    //删除头节点
                    head = head.next;
                    if(head == null) {
                        //只有一个节点的情况下
                        last = null;
                    }else {
                        head.prev = null;
                    }
                }else {
                    //删除中间和尾巴
                    if(cur.next == null) {
                        //尾巴
                        cur.prev.next = cur.next;
                        last = last.prev;
                    }else {
                        cur.prev.next = cur.next;
                        cur.next.prev = cur.prev;
                    }
                }
                //return;
            }
            cur = cur.next;
        }
    }

    public int size() { // 得到单链表的⻓度
        ListNode cur = head;
        int count = 0;
        while (cur != null) {
            count++;
            cur = cur.next;
        }
        return count;
    }

    public void display() {
        ListNode cur = head;
        while (cur != null) {
            System.out.print(cur.val + " ");
            cur = cur.next;
        }
        System.out.println();
    }

    public void clear() {
        ListNode cur = head;
        while (cur != null) {
            ListNode curN = cur.next;
            cur.prev = null;
            cur.next = null;
            cur = curN;
        }
        head = null;
        last = null;
    }
}

import java.util.ArrayList;
import java.util.LinkedList;
import java.util.List;

public class Test {
    public static void main(String[] args) {

        List<Integer> ArrayList = new ArrayList<>();
        ArrayList.add(999);

        LinkedList<Integer> list = new LinkedList<>();
        list.add(12);
        list.add(34); // 尾插元素
        list.add(2, 45); // 在指定下标插入元素
        list.addAll(ArrayList); // 尾插元素
        list.remove(2); //
        list.remove((Integer)999); // 删除第一个遇到的元素
        list.get(0); // 获取指定下标元素
        list.set(0, 999); // 设置指定下标元素
        System.out.println(list.contains(999)); // 判断是否包含某个元素
        System.out.println(list.indexOf(999)); // 返回第一个指定元素所在下标
        System.out.println(list.lastIndexOf(999)); // 返回最后一个指定元素所在下标
        list.subList(0, 1); // 截取部分链表
        list.clear(); // 清空链表
    }
}

import java.util.Iterator;
import java.util.LinkedList;
import java.util.ListIterator;

public class Test {
    public static void main(String[] args) {

        LinkedList<Integer> list = new LinkedList<>();
        list.add(1);
        list.add(2);
        list.add(3);
        list.add(4);
        list.add(5);

        Iterator<Integer> it = list.iterator();
        while (it.hasNext()) {
            System.out.print(it.next() + " ");
        }
        System.out.println();

        Iterator<Integer> lit = list.listIterator();
        while (lit.hasNext()) {
            System.out.print(lit.next() + " ");
        }
        System.out.println();

        ListIterator<Integer> lit2 = list.listIterator(list.size());
        while (lit2.hasPrevious()) {
            System.out.print(lit2.previous() + " ");
        }
        System.out.println();
    }
}

public class OuterClass {

    public int data1; // 数据1
    public static int data2; // 静态数据2

    static class staticInnerClass { // 静态内部类无法访问外部变量
        public void innerMethod() {
            data1 = 1; // error
            data2 = 1;
        }
    }

    public static void main(String[] args) {
        OuterClass.staticInnerClass staticInnerClass = new staticInnerClass(); // 静态类的创建
        staticInnerClass.innerMethod(); // 静态方法的访问
    }
}

interface Greeting {
    void greet();
}

public class OuterClassAnonymous {

    public static void main(String[] args) {

        Greeting greeting = new Greeting() { // 匿名内部类在声明时完成实例化，且只使用一次

            public static int a = 10; // 内部类的静态变量

            @Override
            public void greet() {
                System.out.println("hello");
            }
            
        }; //注意匿名类最后要加分号
    }
}