[java数据结构]单链表

手写单链表，直接上代码

public class SingleLinkedList {
    public static class Node {
        int value;
        Node next;
        public Node(int value){
            this.value = value;
        }
    }
    public Node head;
    //头插法
    public void addFirst(int data){
        Node node = new Node(data);
        node.next  = head;
        head = node;
    }
    //尾插法
    public void addLast(int data) {
        Node node = new Node(data);
        if(head==null){
            head = node;
            return;
        }
        //后面开始处理尾节点
        Node current = head;
        while(current.next!=null){
            current = current.next;
        }
        //此时已经走到了最后一个节点，把最后一个节点与新节点简历引用关联
        current.next = node;
    }
    //任意位置插入,第一个数据节点为0号下标
    public void addIndex(int index, int data){
       //校验index合法性
        checkRange(index);
        //下标为0直接头插
        if (index==0){
            addFirst(data);
            return;
        }
        //下标为size 直接尾插
        if (index ==size()){
            addLast(data);
            return;
        }
        Node prevNode  = findPrevNodeByIndex(index);
        Node node = new Node(data);
//        for (int i = 0; i < index-1; i++) {
//            current = current.next;
//        }
        node.next = prevNode.next;
        prevNode.next = node;
    }

    private Node findPrevNodeByIndex(int index) {
        // 定义一个临时变量，用来遍历
        Node current = head;
        for (int i = 0; i < (index - 1); i++) {
            current = current.next;
        }
        return current;
    }
    private void checkRange(int index) {
        if (index<0||index>size()){
            throw new IndexOutOfBoundsException("下标不合法，index = "+ index);
        }
    }
    //查找是否包含关键字key是否在单链表当中
    public boolean contains(int key){
        Node current = head;
        while(current.next!=null){
            if (current.value==key){
                return true;
            }
            current = current.next;
        }
        return false;
    }

    //得到单链表的长度
    public int size(){
        Node node = head;
        int count = 0;
        while (node!=null){
               count++;
               node = node.next;
        }
        return count;
    }
    //删除第一次出现关键字为key的节点
    public void remove(int key) {
        //如果头节点就是要找的节点
        if (head.value == key) {
            head = head.next;
        }
        // 如果代码已经走到这里了
        Node current = head;
        while (current.next != null) {
            if (current.next.value == key) {
                current.next = current.next.next;
                return;
            }
            current= current.next;
        }
    }
    //删除所有值为key的节点
    public void removeAllKey(int key){
        //首先判断是不是空链表
        if (head==null){
            return;
        }
        //定义两个临时变量,一个用头节点，另一个用头节点的下一个节点
        Node prev = head;
        Node current = prev.next;
        while(current!=null){
            if (current.value==key){
                prev.next = current.next;
            }
            else{
                prev = current;
                current = prev.next;
            }
            current = current.next;
        }
        // 最后处理一下头节点
        if (head.value == key) {
            head = head.next;
        }

    }
    //清空列表
    public void clear(){
        head = null;
    }

    //打印链表
    public void display(){
        Node current = head;
        StringBuilder sb = new StringBuilder();
        sb.append("[");
        while(current!=null){
            sb.append(current.value);
            if (current.next!=null){
                sb.append(", ");
            }
            current = current.next;
        }
        sb.append("]");
        System.out.println(sb.toString());

    }
}