2022年各大厂最新集合Java面试题资料整合及答案

if(对象名 instanceof 接口名){
 
}

String classes = "java.util.LinkedList";

if(Class.forName(classes).newInstance() instanceof List) {
	System.out.println(true);
}else {
	System.out.println(false);
}

public class LinkList {
	public Node head;
	public Node current;

	//方法：向链表中添加数据  
	public void add(int data) {
		// 判断链表为空
		if (head == null) {// 如果头结点为空，说明这个链表还没有创建，那就把新的结点赋给头结点
			head = new Node(data);
			current = head;
		} else {
			// 创建新的结点，放在当前节点的后面（把新的结点合链表进行关联）
			current.next = new Node(data);
			// 把链表的当前索引向后移动一位
			current = current.next; // 此步操作完成之后，current结点指向新添加的那个结点
		}
	}

	//方法：遍历链表（打印输出链表。方法的参数表示从节点node开始进行遍历  
	public void print(Node node) {
		if (node == null) {
			return;
		}

		current = node;
		while (current != null) {
			System.out.println(current.data);
			current = current.next;
		}
	}

	class Node {
		//注：此处的两个成员变量权限不能为private，因为private的权限是仅对本类访问。  
		int data; // 数据域
		Node next;// 指针域

		public Node(int data) {
			this.data = data;
		}
	}

	public static void main(String[] args) {
		LinkList list = new LinkList();
		//向LinkList中添加数据  
		for (int i = 0; i < 10; i++) {
			list.add(i);
		}

		list.print(list.head);// 从head节点开始遍历输出
	}

}

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final Node<K,V> getNode(int hash, Object key) {
    Node<K,V>[] tab; Node<K,V> first, e; int n; K k;
    if ((tab = table) != null && (n = tab.length) > 0 &&
        (first = tab[(n - 1) & hash]) != null) {
        if (first.hash == hash && // always check first node
            ((k = first.key) == key || (key != null && key.equals(k))))
            return first;
        if ((e = first.next) != null) {
            // 第一个结点为红黑树
            if (first instanceof TreeNode)
                return ((TreeNode<K,V>)first).getTreeNode(hash, key);
            // 否则遍历链表
            do {
                if (e.hash == hash &&
                    ((k = e.key) == key || (key != null && key.equals(k))))
                    return e;
            } while ((e = e.next) != null);
        }
    }
    return null;
}

final V putVal(K key, V value, boolean onlyIfAbsent) {
    if (key == null || value == null) throw new NullPointerException();
    int hash = spread(key.hashCode());
    int binCount = 0;
    for (Node<K,V>[] tab = table;;) {
        Node<K,V> f; int n, i, fh;
        if (tab == null || (n = tab.length) == 0)
            tab = initTable();
        else if ((f = tabAt(tab, i = (n - 1) & hash)) == null) {
            if (casTabAt(tab, i, null,
                         new Node<K,V>(hash, key, value, null)))
                break;                   // no lock when adding to empty bin
        }
        else if ((fh = f.hash) == MOVED)
            tab = helpTransfer(tab, f);
        else {
            V oldVal = null;
            // 此处f即为链表的头结点
            synchronized (f) {
                if (tabAt(tab, i) == f) {
                    if (fh >= 0) {
                        binCount = 1;
                        for (Node<K,V> e = f;; ++binCount) {
                            K ek;
                            if (e.hash == hash &&
                                ((ek = e.key) == key ||
                                 (ek != null && key.equals(ek)))) {
                                oldVal = e.val;
                                if (!onlyIfAbsent)
                                    e.val = value;
                                break;
                            }
                            Node<K,V> pred = e;
                            if ((e = e.next) == null) {
                                pred.next = new Node<K,V>(hash, key,
                                                          value, null);
                                break;
                            }
                        }
                    }
                    else if (f instanceof TreeBin) {
                        Node<K,V> p;
                        binCount = 2;
                        if ((p = ((TreeBin<K,V>)f).putTreeVal(hash, key,
                                                       value)) != null) {
                            oldVal = p.val;
                            if (!onlyIfAbsent)
                                p.val = value;
                        }
                    }
                }
            }
            if (binCount != 0) {
                if (binCount >= TREEIFY_THRESHOLD)
                    treeifyBin(tab, i);
                if (oldVal != null)
                    return oldVal;
                break;
            }
        }
    }
    addCount(1L, binCount);
    return null;
}

String[] arrays = new String[20];
Object[] obj = arrays;
obj[0] = new Integer(1); // throws ArrayStoreException at runtime

List<String> list = new ArrayList<>();

for (int i = 0; i < list.size(); i++) {
	System.out.println(list.get(i));
}

//使用for-each循环
for(String obj : list){
	System.out.println(obj);
}

//使用迭代器 iterator
Iterator<String> it = list.iterator();
while(it.hasNext()){
  String obj = it.next();
  System.out.println(obj);
}