Java在Web开发中应用广泛吗？
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本文共计5616个文字，预计阅读时间需要23分钟。
目录
一、LinkedHashMap的继承关系
二、源码分析
1.自我对LinkedHashMap的理解
2.如何实现双向链表的增删改查
（1）增 （2）删 （3）改 （4）查3.遍历
目录
- 一、LinkedHashMap的类继承关系
- 二、源码分析
- 1.自己对LinkedHashMap的理解
- 2.如何做到双向链的增删改查
- (1).增
- (2).删
- (3).改
- (4).查
- 3.遍历
一、LinkedHashMap的类继承关系
二、源码分析
1.自己对LinkedHashMap的理解
从继承关系上，我们看到LinkedHashMap继承了HashMap，它里面的增删改差遍历的逻辑都是使用的HashMap中的，但是LinkedHashMap比HashMap多了一个双向链，这个双向链是从第一个插入的元素开始按照插入顺序，连接起来，所以可以说LinkedHashMap是可以保证插入顺序的。
看图：这里就简单的给大家看一下这个链是啥样的，不画红黑树了
2.如何做到双向链的增删改查
(1).增
1).是在创建新节点的时候，把双向链连接起来，注意有两种节点一个是TreeNode一个普通Node
源码:
Node<K,V> newNode(int hash, K key, V value, Node<K,V> e) { LinkedHashMap.Entry<K,V> p = new LinkedHashMap.Entry<K,V>(hash, key, value, e); linkNodeLast(p); return p; } TreeNode<K,V> newTreeNode(int hash, K key, V value, Node<K,V> next) { TreeNode<K,V> p = new TreeNode<K,V>(hash, key, value, next); linkNodeLast(p); return p; } private void linkNodeLast(LinkedHashMap.Entry<K,V> p) { LinkedHashMap.Entry<K,V> last = tail; tail = p; if (last == null) head = p; else { p.before = last; last.after = p; } } static class Entry<K,V> extends HashMap.Node<K,V> { Entry<K,V> before, after; Entry(int hash, K key, V value, Node<K,V> next) { super(hash, key, value, next); } }
代码太简单了，这里简单描述一下，就是添加新节点会创建Node，有两种Node：TreeNode和普通Node(注意这里多态的使用普通Node和LinedHashMap.Entry和TreeNode的关系看一下就明白了)，在创建之后放到双向链最后面。
2).有好多人说了还有一个afterNodeInsertion方法，这个方法的名字就显示是在插入之后调用的，是不是在这个方法中也有修改链表的逻辑，我们来看这个方法
void afterNodeInsertion(boolean evict) { // possibly remove eldest LinkedHashMap.Entry<K,V> first; if (evict && (first = head) != null && removeEldestEntry(first)) { K key = first.key; removeNode(hash(key), key, null, false, true); } } protected boolean removeEldestEntry(Map.Entry<K,V> eldest) { return false; }
看这个判断，有一个永远是false，也就是说如果我们不重写这个removeEldestEntry方法，那这个afterNodeInsertion方法里的逻辑永远不会执行，那这个玩意儿是干啥的呢，看逻辑是用来移除最早的头节点的，不知道为啥写着么一段，默认不会执行!!!
(2).删
void afterNodeRemoval(Node<K,V> e) { // unlink LinkedHashMap.Entry<K,V> p = (LinkedHashMap.Entry<K,V>)e, b = p.before, a = p.after; // b是当前节点的前一个节点，a是后一个节点 p.before = p.after = null; //先断开当前节点，把当前节点对上一个和下一个节点的引用置为空 if (b == null) //当前节点的前一个节点是null，说明当前节点是头节点，那去掉当前节点之后，当前节点的后一个节点成为了链第一个， // 也就是头节点，当然有可能a也是null，那整个链就是空链，这种写法兼容了a也是null的情况 head = a; else b.after = a; //如果当前节点不是头节点，直接去掉当前节点，当前节点的前一个和后一个连起来 if (a == null) //如果当前节点的后一个节点是null，说明当前节点是尾节点，那把当前节点去掉后，当前节点的前一个节点成为了链的最后一个节点尾节点。 tail = b; else a.before = b;//如果当前节点不是尾节点，直接去掉当前节点，当前节点的前一个和后一个连起来 }
这个删除我们看一下在哪里调用的:
final Node<K,V> removeNode(int hash, Object key, Object value, boolean matchValue, boolean movable) { ... if (node != null && (!matchValue || (v = node.value) == value || (value != null && value.equals(v)))) { if (node instanceof TreeNode) ((TreeNode<K,V>)node).removeTreeNode(this, tab, movable); else if (node == p) tab[index] = node.next; else p.next = node.next; ++modCount; --size; afterNodeRemoval(node); //⭐️⭐️⭐️ return node; } } return null; }
在HashMap的removeNode方法里,当时学习HashMap的时候还是有疑惑的这个方法干啥使的，还是一个没有方法体的空实现方法，现在明白了，就是在给子类重写呢，所以说LinkedHashMap增删改查基本上全是HashMap的逻辑。
(3).改
有几点要注意
1).首先声明一点afterNodeAccess这个方法虽然在HashMap中改变键值对value值的时候都会调用，但是它和改变值没啥关系，真正的改值的逻辑是HashMap中的例如putVal方法，这个方法只是在改完值之后调用一下
final V putVal(int hash, K key, V value, boolean onlyIfAbsent, boolean evict) { ... if (e != null) { // existing mapping for key V oldValue = e.value; if (!onlyIfAbsent || oldValue == null) e.value = value; afterNodeAccess(e); //⭐️⭐️⭐️⭐️ return oldValue; } } ++modCount; if (++size > threshold) resize(); afterNodeInsertion(evict); return null; }
2).afterNodeAccess的真正作用是把刚刚访问过的节点放到双向链的末尾，一旦执行这个方法那就会打乱我们由插入顺序形成的链表，这个逻辑执不执行由accessOrder变量控制
/** * 此方法的作用是将刚刚访问的节点e放到链表的尾端 */ void afterNodeAccess(Node<K,V> e) { LinkedHashMap.Entry<K,V> last; // accessOrder = true 时 访问节点后才需要置于尾端 // 如果e本身就在尾端，那就不需要操作 if (accessOrder && (last = tail) != e) { // 记录节点e、e的前驱、e的后继 LinkedHashMap.Entry<K,V> p = (LinkedHashMap.Entry<K,V>)e, b = p.before, a = p.after; // 第一步：现将p.after置空 p.after = null; // 第二步：将e的前驱.after 连接上e的后继 if (b == null) // b记录e的前驱，前驱为null，则e在表头，head置为e的后继 head = a; else // 否则 e的前驱.after = e的后继 b.after = a; // 第三步：将e的后继.before 连接上e的前驱 if (a != null) // e的后继 != null，将e后继.before = e的前驱 a.before = b; else // 否则e的后继 == null，即在e表尾（这里有点多余，前面已经判断在表尾不操作。。。） last = b; // 第四步：将节点e接入到链表的尾端 if (last == null) // last == null,链表为空，head = p head = p; else { // p.before 指向last（链表尾端）,尾端.after = p p.before = last; last.after = p; } // 第四步：更新链表新尾端tail tail = p; // 链表结构性调整，修改次数自增 ++modCount; } }
注意，到底会不会执行这个方法，是由accessOrder变量控制,而这个变量只有在构造方法中指定才会为ture，其他的构造方法默认都是false不执行这段逻辑:
public LinkedHashMap(int initialCapacity, float loadFactor) { super(initialCapacity, loadFactor); accessOrder = false; } /** * Constructs an empty insertion-ordered <tt>LinkedHashMap</tt> instance * with the specified initial capacity and a default load factor (0.75). * * @param initialCapacity the initial capacity * @throws IllegalArgumentException if the initial capacity is negative */ public LinkedHashMap(int initialCapacity) { super(initialCapacity); accessOrder = false; } /** * Constructs an empty insertion-ordered <tt>LinkedHashMap</tt> instance * with the default initial capacity (16) and load factor (0.75). */ public LinkedHashMap() { super(); accessOrder = false; } /** * Constructs an insertion-ordered <tt>LinkedHashMap</tt> instance with * the same mappings as the specified map. The <tt>LinkedHashMap</tt> * instance is created with a default load factor (0.75) and an initial * capacity sufficient to hold the mappings in the specified map. * * @param m the map whose mappings are to be placed in this map * @throws NullPointerException if the specified map is null */ public LinkedHashMap(Map<? extends K, ? extends V> m) { super(); accessOrder = false; putMapEntries(m, false); } /** * Constructs an empty <tt>LinkedHashMap</tt> instance with the * specified initial capacity, load factor and ordering mode. * * @param initialCapacity the initial capacity * @param loadFactor the load factor * @param accessOrder the ordering mode - <tt>true</tt> for * access-order, <tt>false</tt> for insertion-order * @throws IllegalArgumentException if the initial capacity is negative * or the load factor is nonpositive */ public LinkedHashMap(int initialCapacity, float loadFactor, boolean accessOrder) { super(initialCapacity, loadFactor); this.accessOrder = accessOrder; }
(4).查
public V get(Object key) { Node<K,V> e; if ((e = getNode(hash(key), key)) == null) return null; if (accessOrder) afterNodeAccess(e); return e.value; } /** * {@inheritDoc} */ public V getOrDefault(Object key, V defaultValue) { Node<K,V> e; if ((e = getNode(hash(key), key)) == null) return defaultValue; if (accessOrder) afterNodeAccess(e); return e.value; }
没啥好说的，都是调用的HashMap的代码。
3.遍历
遍历 和hashMap一样，只不过重写了一些方法，重写是为了按插入顺序遍历
public Set<K> keySet() { Set<K> ks = keySet; if (ks == null) { ks = new LinkedKeySet(); keySet = ks; } return ks; } final class LinkedKeySet extends AbstractSet<K> { public final int size() { return size; } public final void clear() { LinkedHashMap.this.clear(); } public final Iterator<K> iterator() { return new LinkedKeyIterator(); } public final boolean contains(Object o) { return containsKey(o); } public final boolean remove(Object key) { return removeNode(hash(key), key, null, false, true) != null; } public final Spliterator<K> spliterator() { return Spliterators.spliterator(this, Spliterator.SIZED | Spliterator.ORDERED | Spliterator.DISTINCT); } public final void forEach(Consumer<? super K> action) { if (action == null) throw new NullPointerException(); int mc = modCount; for (LinkedHashMap.Entry<K,V> e = head; e != null; e = e.after) action.accept(e.key); if (modCount != mc) throw new ConcurrentModificationException(); } } public Collection<V> values() { Collection<V> vs = values; if (vs == null) { vs = new LinkedValues(); values = vs; } return vs; } final class LinkedValues extends AbstractCollection<V> { public final int size() { return size; } public final void clear() { LinkedHashMap.this.clear(); } public final Iterator<V> iterator() { return new LinkedValueIterator(); } public final boolean contains(Object o) { return containsValue(o); } public final Spliterator<V> spliterator() { return Spliterators.spliterator(this, Spliterator.SIZED | Spliterator.ORDERED); } public final void forEach(Consumer<? super V> action) { if (action == null) throw new NullPointerException(); int mc = modCount; for (LinkedHashMap.Entry<K,V> e = head; e != null; e = e.after) action.accept(e.value); if (modCount != mc) throw new ConcurrentModificationException(); } } /** * Returns a {@link Set} view of the mappings contained in this map. * The set is backed by the map, so changes to the map are * reflected in the set, and vice-versa. If the map is modified * while an iteration over the set is in progress (except through * the iterator's own <tt>remove</tt> operation, or through the * <tt>setValue</tt> operation on a map entry returned by the * iterator) the results of the iteration are undefined. The set * supports element removal, which removes the corresponding * mapping from the map, via the <tt>Iterator.remove</tt>, * <tt>Set.remove</tt>, <tt>removeAll</tt>, <tt>retainAll</tt> and * <tt>clear</tt> operations. It does not support the * <tt>add</tt> or <tt>addAll</tt> operations. * Its {@link Spliterator} typically provides faster sequential * performance but much poorer parallel performance than that of * {@code HashMap}. * * @return a set view of the mappings contained in this map */ public Set<Map.Entry<K,V>> entrySet() { Set<Map.Entry<K,V>> es; return (es = entrySet) == null ? (entrySet = new LinkedEntrySet()) : es; } final class LinkedEntrySet extends AbstractSet<Map.Entry<K,V>> { public final int size() { return size; } public final void clear() { LinkedHashMap.this.clear(); } public final Iterator<Map.Entry<K,V>> iterator() { return new LinkedEntryIterator(); } public final boolean contains(Object o) { if (!(o instanceof Map.Entry)) return false; Map.Entry<?,?> e = (Map.Entry<?,?>) o; Object key = e.getKey(); Node<K,V> candidate = getNode(hash(key), key); return candidate != null && candidate.equals(e); } public final boolean remove(Object o) { if (o instanceof Map.Entry) { Map.Entry<?,?> e = (Map.Entry<?,?>) o; Object key = e.getKey(); Object value = e.getValue(); return removeNode(hash(key), key, value, true, true) != null; } return false; } public final Spliterator<Map.Entry<K,V>> spliterator() { return Spliterators.spliterator(this, Spliterator.SIZED | Spliterator.ORDERED | Spliterator.DISTINCT); } public final void forEach(Consumer<? super Map.Entry<K,V>> action) { if (action == null) throw new NullPointerException(); int mc = modCount; for (LinkedHashMap.Entry<K,V> e = head; e != null; e = e.after) action.accept(e); if (modCount != mc) throw new ConcurrentModificationException(); } } // Map overrides public void forEach(BiConsumer<? super K, ? super V> action) { if (action == null) throw new NullPointerException(); int mc = modCount; for (LinkedHashMap.Entry<K,V> e = head; e != null; e = e.after) action.accept(e.key, e.value); if (modCount != mc) throw new ConcurrentModificationException(); } public void replaceAll(BiFunction<? super K, ? super V, ? extends V> function) { if (function == null) throw new NullPointerException(); int mc = modCount; for (LinkedHashMap.Entry<K,V> e = head; e != null; e = e.after) e.value = function.apply(e.key, e.value); if (modCount != mc) throw new ConcurrentModificationException(); }
简单测试一下，是不是按顺序遍历:
public class LinkedHashMapTestMain { public static void main(String[] args) { LinkedHashMap<String,String> linkedHashMap = new LinkedHashMap<>(); for (int i = 0; i < 100; i++) { linkedHashMap.put(i + "", i + ""); } //第一种entrySet Set<Map.Entry<String, String>> entrySet = linkedHashMap.entrySet(); Iterator<Map.Entry<String, String>> iterator = entrySet.iterator(); while (iterator.hasNext()) { Map.Entry<String, String> entry = iterator.next(); System.out.println("entrySet: " + "key: " + entry.getKey() + "--- value: " + entry.getValue()); } for (Map.Entry<String, String> entry : entrySet){ System.out.println("entrySet forEach循环: " + "key: " + entry.getKey() + "--- value: " + entry.getValue()); } //第二种keySet Set<String> keySet = linkedHashMap.keySet(); Iterator<String> keySetIterator = keySet.iterator(); while (keySetIterator.hasNext()){ String key = keySetIterator.next(); System.out.println("keySet: " + "key: " + key + "--- value: " + linkedHashMap.get(key)); } for (String key : keySet){ System.out.println("keySet forEach循环: " + "key: " + key + "--- value: " + linkedHashMap.get(key)); } } }
执行结果:
entrySet: key: 0--- value: 0
entrySet: key: 1--- value: 1
entrySet: key: 2--- value: 2
entrySet: key: 3--- value: 3
entrySet: key: 4--- value: 4
entrySet: key: 5--- value: 5
entrySet: key: 6--- value: 6
entrySet: key: 7--- value: 7
entrySet: key: 8--- value: 8
entrySet: key: 9--- value: 9
entrySet: key: 10--- value: 10
entrySet: key: 11--- value: 11
entrySet: key: 12--- value: 12
entrySet: key: 13--- value: 13
entrySet: key: 14--- value: 14
entrySet: key: 15--- value: 15
entrySet: key: 16--- value: 16
entrySet: key: 17--- value: 17
entrySet: key: 18--- value: 18
entrySet: key: 19--- value: 19
entrySet: key: 20--- value: 20
entrySet: key: 21--- value: 21
entrySet: key: 22--- value: 22
entrySet: key: 23--- value: 23
entrySet: key: 24--- value: 24
entrySet: key: 25--- value: 25
entrySet: key: 26--- value: 26
entrySet: key: 27--- value: 27
entrySet: key: 28--- value: 28
entrySet: key: 29--- value: 29
entrySet: key: 30--- value: 30
entrySet: key: 31--- value: 31
entrySet: key: 32--- value: 32
entrySet: key: 33--- value: 33
entrySet: key: 34--- value: 34
entrySet: key: 35--- value: 35
entrySet: key: 36--- value: 36
entrySet: key: 37--- value: 37
entrySet: key: 38--- value: 38
entrySet: key: 39--- value: 39
entrySet: key: 40--- value: 40
entrySet: key: 41--- value: 41
entrySet: key: 42--- value: 42
entrySet: key: 43--- value: 43
entrySet: key: 44--- value: 44
entrySet: key: 45--- value: 45
entrySet: key: 46--- value: 46
entrySet: key: 47--- value: 47
entrySet: key: 48--- value: 48
entrySet: key: 49--- value: 49
entrySet: key: 50--- value: 50
entrySet: key: 51--- value: 51
entrySet: key: 52--- value: 52
entrySet: key: 53--- value: 53
entrySet: key: 54--- value: 54
entrySet: key: 55--- value: 55
entrySet: key: 56--- value: 56
entrySet: key: 57--- value: 57
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entrySet: key: 60--- value: 60
entrySet: key: 61--- value: 61
entrySet: key: 62--- value: 62
entrySet: key: 63--- value: 63
entrySet: key: 64--- value: 64
entrySet: key: 65--- value: 65
entrySet: key: 66--- value: 66
entrySet: key: 67--- value: 67
entrySet: key: 68--- value: 68
entrySet: key: 69--- value: 69
entrySet: key: 70--- value: 70
entrySet: key: 71--- value: 71
entrySet: key: 72--- value: 72
entrySet: key: 73--- value: 73
entrySet: key: 74--- value: 74
entrySet: key: 75--- value: 75
entrySet: key: 76--- value: 76
entrySet: key: 77--- value: 77
entrySet: key: 78--- value: 78
entrySet: key: 79--- value: 79
entrySet: key: 80--- value: 80
entrySet: key: 81--- value: 81
entrySet: key: 82--- value: 82
entrySet: key: 83--- value: 83
entrySet: key: 84--- value: 84
entrySet: key: 85--- value: 85
entrySet: key: 86--- value: 86
entrySet: key: 87--- value: 87
entrySet: key: 88--- value: 88
entrySet: key: 89--- value: 89
entrySet: key: 90--- value: 90
entrySet: key: 91--- value: 91
entrySet: key: 92--- value: 92
entrySet: key: 93--- value: 93
entrySet: key: 94--- value: 94
entrySet: key: 95--- value: 95
entrySet: key: 96--- value: 96
entrySet: key: 97--- value: 97
entrySet: key: 98--- value: 98
entrySet: key: 99--- value: 99
entrySet forEach循环: key: 0--- value: 0
entrySet forEach循环: key: 1--- value: 1
entrySet forEach循环: key: 2--- value: 2
entrySet forEach循环: key: 3--- value: 3
entrySet forEach循环: key: 4--- value: 4
entrySet forEach循环: key: 5--- value: 5
entrySet forEach循环: key: 6--- value: 6
entrySet forEach循环: key: 7--- value: 7
entrySet forEach循环: key: 8--- value: 8
entrySet forEach循环: key: 9--- value: 9
entrySet forEach循环: key: 10--- value: 10
entrySet forEach循环: key: 11--- value: 11
entrySet forEach循环: key: 12--- value: 12
entrySet forEach循环: key: 13--- value: 13
entrySet forEach循环: key: 14--- value: 14
entrySet forEach循环: key: 15--- value: 15
entrySet forEach循环: key: 16--- value: 16
entrySet forEach循环: key: 17--- value: 17
entrySet forEach循环: key: 18--- value: 18
entrySet forEach循环: key: 19--- value: 19
entrySet forEach循环: key: 20--- value: 20
entrySet forEach循环: key: 21--- value: 21
entrySet forEach循环: key: 22--- value: 22
entrySet forEach循环: key: 23--- value: 23
entrySet forEach循环: key: 24--- value: 24
entrySet forEach循环: key: 25--- value: 25
entrySet forEach循环: key: 26--- value: 26
entrySet forEach循环: key: 27--- value: 27
entrySet forEach循环: key: 28--- value: 28
entrySet forEach循环: key: 29--- value: 29
entrySet forEach循环: key: 30--- value: 30
entrySet forEach循环: key: 31--- value: 31
entrySet forEach循环: key: 32--- value: 32
entrySet forEach循环: key: 33--- value: 33
entrySet forEach循环: key: 34--- value: 34
entrySet forEach循环: key: 35--- value: 35
entrySet forEach循环: key: 36--- value: 36
entrySet forEach循环: key: 37--- value: 37
entrySet forEach循环: key: 38--- value: 38
entrySet forEach循环: key: 39--- value: 39
entrySet forEach循环: key: 40--- value: 40
entrySet forEach循环: key: 41--- value: 41
entrySet forEach循环: key: 42--- value: 42
entrySet forEach循环: key: 43--- value: 43
entrySet forEach循环: key: 44--- value: 44
entrySet forEach循环: key: 45--- value: 45
entrySet forEach循环: key: 46--- value: 46
entrySet forEach循环: key: 47--- value: 47
entrySet forEach循环: key: 48--- value: 48
entrySet forEach循环: key: 49--- value: 49
entrySet forEach循环: key: 50--- value: 50
entrySet forEach循环: key: 51--- value: 51
entrySet forEach循环: key: 52--- value: 52
entrySet forEach循环: key: 53--- value: 53
entrySet forEach循环: key: 54--- value: 54
entrySet forEach循环: key: 55--- value: 55
entrySet forEach循环: key: 56--- value: 56
entrySet forEach循环: key: 57--- value: 57
entrySet forEach循环: key: 58--- value: 58
entrySet forEach循环: key: 59--- value: 59
entrySet forEach循环: key: 60--- value: 60
entrySet forEach循环: key: 61--- value: 61
entrySet forEach循环: key: 62--- value: 62
entrySet forEach循环: key: 63--- value: 63
entrySet forEach循环: key: 64--- value: 64
entrySet forEach循环: key: 65--- value: 65
entrySet forEach循环: key: 66--- value: 66
entrySet forEach循环: key: 67--- value: 67
entrySet forEach循环: key: 68--- value: 68
entrySet forEach循环: key: 69--- value: 69
entrySet forEach循环: key: 70--- value: 70
entrySet forEach循环: key: 71--- value: 71
entrySet forEach循环: key: 72--- value: 72
entrySet forEach循环: key: 73--- value: 73
entrySet forEach循环: key: 74--- value: 74
entrySet forEach循环: key: 75--- value: 75
entrySet forEach循环: key: 76--- value: 76
entrySet forEach循环: key: 77--- value: 77
entrySet forEach循环: key: 78--- value: 78
entrySet forEach循环: key: 79--- value: 79
entrySet forEach循环: key: 80--- value: 80
entrySet forEach循环: key: 81--- value: 81
entrySet forEach循环: key: 82--- value: 82
entrySet forEach循环: key: 83--- value: 83
entrySet forEach循环: key: 84--- value: 84
entrySet forEach循环: key: 85--- value: 85
entrySet forEach循环: key: 86--- value: 86
entrySet forEach循环: key: 87--- value: 87
entrySet forEach循环: key: 88--- value: 88
entrySet forEach循环: key: 89--- value: 89
entrySet forEach循环: key: 90--- value: 90
entrySet forEach循环: key: 91--- value: 91
entrySet forEach循环: key: 92--- value: 92
entrySet forEach循环: key: 93--- value: 93
entrySet forEach循环: key: 94--- value: 94
entrySet forEach循环: key: 95--- value: 95
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keySet forEach循环: key: 0--- value: 0
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本文共计5616个文字，预计阅读时间需要23分钟。
目录
一、LinkedHashMap的继承关系
二、源码分析
1.自我对LinkedHashMap的理解
2.如何实现双向链表的增删改查
（1）增 （2）删 （3）改 （4）查3.遍历
目录
- 一、LinkedHashMap的类继承关系
- 二、源码分析
- 1.自己对LinkedHashMap的理解
- 2.如何做到双向链的增删改查
- (1).增
- (2).删
- (3).改
- (4).查
- 3.遍历
一、LinkedHashMap的类继承关系
二、源码分析
1.自己对LinkedHashMap的理解
从继承关系上，我们看到LinkedHashMap继承了HashMap，它里面的增删改差遍历的逻辑都是使用的HashMap中的，但是LinkedHashMap比HashMap多了一个双向链，这个双向链是从第一个插入的元素开始按照插入顺序，连接起来，所以可以说LinkedHashMap是可以保证插入顺序的。
看图：这里就简单的给大家看一下这个链是啥样的，不画红黑树了
2.如何做到双向链的增删改查
(1).增
1).是在创建新节点的时候，把双向链连接起来，注意有两种节点一个是TreeNode一个普通Node
源码:
Node<K,V> newNode(int hash, K key, V value, Node<K,V> e) { LinkedHashMap.Entry<K,V> p = new LinkedHashMap.Entry<K,V>(hash, key, value, e); linkNodeLast(p); return p; } TreeNode<K,V> newTreeNode(int hash, K key, V value, Node<K,V> next) { TreeNode<K,V> p = new TreeNode<K,V>(hash, key, value, next); linkNodeLast(p); return p; } private void linkNodeLast(LinkedHashMap.Entry<K,V> p) { LinkedHashMap.Entry<K,V> last = tail; tail = p; if (last == null) head = p; else { p.before = last; last.after = p; } } static class Entry<K,V> extends HashMap.Node<K,V> { Entry<K,V> before, after; Entry(int hash, K key, V value, Node<K,V> next) { super(hash, key, value, next); } }
代码太简单了，这里简单描述一下，就是添加新节点会创建Node，有两种Node：TreeNode和普通Node(注意这里多态的使用普通Node和LinedHashMap.Entry和TreeNode的关系看一下就明白了)，在创建之后放到双向链最后面。
2).有好多人说了还有一个afterNodeInsertion方法，这个方法的名字就显示是在插入之后调用的，是不是在这个方法中也有修改链表的逻辑，我们来看这个方法
void afterNodeInsertion(boolean evict) { // possibly remove eldest LinkedHashMap.Entry<K,V> first; if (evict && (first = head) != null && removeEldestEntry(first)) { K key = first.key; removeNode(hash(key), key, null, false, true); } } protected boolean removeEldestEntry(Map.Entry<K,V> eldest) { return false; }
看这个判断，有一个永远是false，也就是说如果我们不重写这个removeEldestEntry方法，那这个afterNodeInsertion方法里的逻辑永远不会执行，那这个玩意儿是干啥的呢，看逻辑是用来移除最早的头节点的，不知道为啥写着么一段，默认不会执行!!!
(2).删
void afterNodeRemoval(Node<K,V> e) { // unlink LinkedHashMap.Entry<K,V> p = (LinkedHashMap.Entry<K,V>)e, b = p.before, a = p.after; // b是当前节点的前一个节点，a是后一个节点 p.before = p.after = null; //先断开当前节点，把当前节点对上一个和下一个节点的引用置为空 if (b == null) //当前节点的前一个节点是null，说明当前节点是头节点，那去掉当前节点之后，当前节点的后一个节点成为了链第一个， // 也就是头节点，当然有可能a也是null，那整个链就是空链，这种写法兼容了a也是null的情况 head = a; else b.after = a; //如果当前节点不是头节点，直接去掉当前节点，当前节点的前一个和后一个连起来 if (a == null) //如果当前节点的后一个节点是null，说明当前节点是尾节点，那把当前节点去掉后，当前节点的前一个节点成为了链的最后一个节点尾节点。 tail = b; else a.before = b;//如果当前节点不是尾节点，直接去掉当前节点，当前节点的前一个和后一个连起来 }
这个删除我们看一下在哪里调用的:
final Node<K,V> removeNode(int hash, Object key, Object value, boolean matchValue, boolean movable) { ... if (node != null && (!matchValue || (v = node.value) == value || (value != null && value.equals(v)))) { if (node instanceof TreeNode) ((TreeNode<K,V>)node).removeTreeNode(this, tab, movable); else if (node == p) tab[index] = node.next; else p.next = node.next; ++modCount; --size; afterNodeRemoval(node); //⭐️⭐️⭐️ return node; } } return null; }
在HashMap的removeNode方法里,当时学习HashMap的时候还是有疑惑的这个方法干啥使的，还是一个没有方法体的空实现方法，现在明白了，就是在给子类重写呢，所以说LinkedHashMap增删改查基本上全是HashMap的逻辑。
(3).改
有几点要注意
1).首先声明一点afterNodeAccess这个方法虽然在HashMap中改变键值对value值的时候都会调用，但是它和改变值没啥关系，真正的改值的逻辑是HashMap中的例如putVal方法，这个方法只是在改完值之后调用一下
final V putVal(int hash, K key, V value, boolean onlyIfAbsent, boolean evict) { ... if (e != null) { // existing mapping for key V oldValue = e.value; if (!onlyIfAbsent || oldValue == null) e.value = value; afterNodeAccess(e); //⭐️⭐️⭐️⭐️ return oldValue; } } ++modCount; if (++size > threshold) resize(); afterNodeInsertion(evict); return null; }
2).afterNodeAccess的真正作用是把刚刚访问过的节点放到双向链的末尾，一旦执行这个方法那就会打乱我们由插入顺序形成的链表，这个逻辑执不执行由accessOrder变量控制
/** * 此方法的作用是将刚刚访问的节点e放到链表的尾端 */ void afterNodeAccess(Node<K,V> e) { LinkedHashMap.Entry<K,V> last; // accessOrder = true 时 访问节点后才需要置于尾端 // 如果e本身就在尾端，那就不需要操作 if (accessOrder && (last = tail) != e) { // 记录节点e、e的前驱、e的后继 LinkedHashMap.Entry<K,V> p = (LinkedHashMap.Entry<K,V>)e, b = p.before, a = p.after; // 第一步：现将p.after置空 p.after = null; // 第二步：将e的前驱.after 连接上e的后继 if (b == null) // b记录e的前驱，前驱为null，则e在表头，head置为e的后继 head = a; else // 否则 e的前驱.after = e的后继 b.after = a; // 第三步：将e的后继.before 连接上e的前驱 if (a != null) // e的后继 != null，将e后继.before = e的前驱 a.before = b; else // 否则e的后继 == null，即在e表尾（这里有点多余，前面已经判断在表尾不操作。。。） last = b; // 第四步：将节点e接入到链表的尾端 if (last == null) // last == null,链表为空，head = p head = p; else { // p.before 指向last（链表尾端）,尾端.after = p p.before = last; last.after = p; } // 第四步：更新链表新尾端tail tail = p; // 链表结构性调整，修改次数自增 ++modCount; } }
注意，到底会不会执行这个方法，是由accessOrder变量控制,而这个变量只有在构造方法中指定才会为ture，其他的构造方法默认都是false不执行这段逻辑:
public LinkedHashMap(int initialCapacity, float loadFactor) { super(initialCapacity, loadFactor); accessOrder = false; } /** * Constructs an empty insertion-ordered <tt>LinkedHashMap</tt> instance * with the specified initial capacity and a default load factor (0.75). * * @param initialCapacity the initial capacity * @throws IllegalArgumentException if the initial capacity is negative */ public LinkedHashMap(int initialCapacity) { super(initialCapacity); accessOrder = false; } /** * Constructs an empty insertion-ordered <tt>LinkedHashMap</tt> instance * with the default initial capacity (16) and load factor (0.75). */ public LinkedHashMap() { super(); accessOrder = false; } /** * Constructs an insertion-ordered <tt>LinkedHashMap</tt> instance with * the same mappings as the specified map. The <tt>LinkedHashMap</tt> * instance is created with a default load factor (0.75) and an initial * capacity sufficient to hold the mappings in the specified map. * * @param m the map whose mappings are to be placed in this map * @throws NullPointerException if the specified map is null */ public LinkedHashMap(Map<? extends K, ? extends V> m) { super(); accessOrder = false; putMapEntries(m, false); } /** * Constructs an empty <tt>LinkedHashMap</tt> instance with the * specified initial capacity, load factor and ordering mode. * * @param initialCapacity the initial capacity * @param loadFactor the load factor * @param accessOrder the ordering mode - <tt>true</tt> for * access-order, <tt>false</tt> for insertion-order * @throws IllegalArgumentException if the initial capacity is negative * or the load factor is nonpositive */ public LinkedHashMap(int initialCapacity, float loadFactor, boolean accessOrder) { super(initialCapacity, loadFactor); this.accessOrder = accessOrder; }
(4).查
public V get(Object key) { Node<K,V> e; if ((e = getNode(hash(key), key)) == null) return null; if (accessOrder) afterNodeAccess(e); return e.value; } /** * {@inheritDoc} */ public V getOrDefault(Object key, V defaultValue) { Node<K,V> e; if ((e = getNode(hash(key), key)) == null) return defaultValue; if (accessOrder) afterNodeAccess(e); return e.value; }
没啥好说的，都是调用的HashMap的代码。
3.遍历
遍历 和hashMap一样，只不过重写了一些方法，重写是为了按插入顺序遍历
public Set<K> keySet() { Set<K> ks = keySet; if (ks == null) { ks = new LinkedKeySet(); keySet = ks; } return ks; } final class LinkedKeySet extends AbstractSet<K> { public final int size() { return size; } public final void clear() { LinkedHashMap.this.clear(); } public final Iterator<K> iterator() { return new LinkedKeyIterator(); } public final boolean contains(Object o) { return containsKey(o); } public final boolean remove(Object key) { return removeNode(hash(key), key, null, false, true) != null; } public final Spliterator<K> spliterator() { return Spliterators.spliterator(this, Spliterator.SIZED | Spliterator.ORDERED | Spliterator.DISTINCT); } public final void forEach(Consumer<? super K> action) { if (action == null) throw new NullPointerException(); int mc = modCount; for (LinkedHashMap.Entry<K,V> e = head; e != null; e = e.after) action.accept(e.key); if (modCount != mc) throw new ConcurrentModificationException(); } } public Collection<V> values() { Collection<V> vs = values; if (vs == null) { vs = new LinkedValues(); values = vs; } return vs; } final class LinkedValues extends AbstractCollection<V> { public final int size() { return size; } public final void clear() { LinkedHashMap.this.clear(); } public final Iterator<V> iterator() { return new LinkedValueIterator(); } public final boolean contains(Object o) { return containsValue(o); } public final Spliterator<V> spliterator() { return Spliterators.spliterator(this, Spliterator.SIZED | Spliterator.ORDERED); } public final void forEach(Consumer<? super V> action) { if (action == null) throw new NullPointerException(); int mc = modCount; for (LinkedHashMap.Entry<K,V> e = head; e != null; e = e.after) action.accept(e.value); if (modCount != mc) throw new ConcurrentModificationException(); } } /** * Returns a {@link Set} view of the mappings contained in this map. * The set is backed by the map, so changes to the map are * reflected in the set, and vice-versa. If the map is modified * while an iteration over the set is in progress (except through * the iterator's own <tt>remove</tt> operation, or through the * <tt>setValue</tt> operation on a map entry returned by the * iterator) the results of the iteration are undefined. The set * supports element removal, which removes the corresponding * mapping from the map, via the <tt>Iterator.remove</tt>, * <tt>Set.remove</tt>, <tt>removeAll</tt>, <tt>retainAll</tt> and * <tt>clear</tt> operations. It does not support the * <tt>add</tt> or <tt>addAll</tt> operations. * Its {@link Spliterator} typically provides faster sequential * performance but much poorer parallel performance than that of * {@code HashMap}. * * @return a set view of the mappings contained in this map */ public Set<Map.Entry<K,V>> entrySet() { Set<Map.Entry<K,V>> es; return (es = entrySet) == null ? (entrySet = new LinkedEntrySet()) : es; } final class LinkedEntrySet extends AbstractSet<Map.Entry<K,V>> { public final int size() { return size; } public final void clear() { LinkedHashMap.this.clear(); } public final Iterator<Map.Entry<K,V>> iterator() { return new LinkedEntryIterator(); } public final boolean contains(Object o) { if (!(o instanceof Map.Entry)) return false; Map.Entry<?,?> e = (Map.Entry<?,?>) o; Object key = e.getKey(); Node<K,V> candidate = getNode(hash(key), key); return candidate != null && candidate.equals(e); } public final boolean remove(Object o) { if (o instanceof Map.Entry) { Map.Entry<?,?> e = (Map.Entry<?,?>) o; Object key = e.getKey(); Object value = e.getValue(); return removeNode(hash(key), key, value, true, true) != null; } return false; } public final Spliterator<Map.Entry<K,V>> spliterator() { return Spliterators.spliterator(this, Spliterator.SIZED | Spliterator.ORDERED | Spliterator.DISTINCT); } public final void forEach(Consumer<? super Map.Entry<K,V>> action) { if (action == null) throw new NullPointerException(); int mc = modCount; for (LinkedHashMap.Entry<K,V> e = head; e != null; e = e.after) action.accept(e); if (modCount != mc) throw new ConcurrentModificationException(); } } // Map overrides public void forEach(BiConsumer<? super K, ? super V> action) { if (action == null) throw new NullPointerException(); int mc = modCount; for (LinkedHashMap.Entry<K,V> e = head; e != null; e = e.after) action.accept(e.key, e.value); if (modCount != mc) throw new ConcurrentModificationException(); } public void replaceAll(BiFunction<? super K, ? super V, ? extends V> function) { if (function == null) throw new NullPointerException(); int mc = modCount; for (LinkedHashMap.Entry<K,V> e = head; e != null; e = e.after) e.value = function.apply(e.key, e.value); if (modCount != mc) throw new ConcurrentModificationException(); }
简单测试一下，是不是按顺序遍历:
public class LinkedHashMapTestMain { public static void main(String[] args) { LinkedHashMap<String,String> linkedHashMap = new LinkedHashMap<>(); for (int i = 0; i < 100; i++) { linkedHashMap.put(i + "", i + ""); } //第一种entrySet Set<Map.Entry<String, String>> entrySet = linkedHashMap.entrySet(); Iterator<Map.Entry<String, String>> iterator = entrySet.iterator(); while (iterator.hasNext()) { Map.Entry<String, String> entry = iterator.next(); System.out.println("entrySet: " + "key: " + entry.getKey() + "--- value: " + entry.getValue()); } for (Map.Entry<String, String> entry : entrySet){ System.out.println("entrySet forEach循环: " + "key: " + entry.getKey() + "--- value: " + entry.getValue()); } //第二种keySet Set<String> keySet = linkedHashMap.keySet(); Iterator<String> keySetIterator = keySet.iterator(); while (keySetIterator.hasNext()){ String key = keySetIterator.next(); System.out.println("keySet: " + "key: " + key + "--- value: " + linkedHashMap.get(key)); } for (String key : keySet){ System.out.println("keySet forEach循环: " + "key: " + key + "--- value: " + linkedHashMap.get(key)); } } }
执行结果:
entrySet: key: 0--- value: 0
entrySet: key: 1--- value: 1
entrySet: key: 2--- value: 2
entrySet: key: 3--- value: 3
entrySet: key: 4--- value: 4
entrySet: key: 5--- value: 5
entrySet: key: 6--- value: 6
entrySet: key: 7--- value: 7
entrySet: key: 8--- value: 8
entrySet: key: 9--- value: 9
entrySet: key: 10--- value: 10
entrySet: key: 11--- value: 11
entrySet: key: 12--- value: 12
entrySet: key: 13--- value: 13
entrySet: key: 14--- value: 14
entrySet: key: 15--- value: 15
entrySet: key: 16--- value: 16
entrySet: key: 17--- value: 17
entrySet: key: 18--- value: 18
entrySet: key: 19--- value: 19
entrySet: key: 20--- value: 20
entrySet: key: 21--- value: 21
entrySet: key: 22--- value: 22
entrySet: key: 23--- value: 23
entrySet: key: 24--- value: 24
entrySet: key: 25--- value: 25
entrySet: key: 26--- value: 26
entrySet: key: 27--- value: 27
entrySet: key: 28--- value: 28
entrySet: key: 29--- value: 29
entrySet: key: 30--- value: 30
entrySet: key: 31--- value: 31
entrySet: key: 32--- value: 32
entrySet: key: 33--- value: 33
entrySet: key: 34--- value: 34
entrySet: key: 35--- value: 35
entrySet: key: 36--- value: 36
entrySet: key: 37--- value: 37
entrySet: key: 38--- value: 38
entrySet: key: 39--- value: 39
entrySet: key: 40--- value: 40
entrySet: key: 41--- value: 41
entrySet: key: 42--- value: 42
entrySet: key: 43--- value: 43
entrySet: key: 44--- value: 44
entrySet: key: 45--- value: 45
entrySet: key: 46--- value: 46
entrySet: key: 47--- value: 47
entrySet: key: 48--- value: 48
entrySet: key: 49--- value: 49
entrySet: key: 50--- value: 50
entrySet: key: 51--- value: 51
entrySet: key: 52--- value: 52
entrySet: key: 53--- value: 53
entrySet: key: 54--- value: 54
entrySet: key: 55--- value: 55
entrySet: key: 56--- value: 56
entrySet: key: 57--- value: 57
entrySet: key: 58--- value: 58
entrySet: key: 59--- value: 59
entrySet: key: 60--- value: 60
entrySet: key: 61--- value: 61
entrySet: key: 62--- value: 62
entrySet: key: 63--- value: 63
entrySet: key: 64--- value: 64
entrySet: key: 65--- value: 65
entrySet: key: 66--- value: 66
entrySet: key: 67--- value: 67
entrySet: key: 68--- value: 68
entrySet: key: 69--- value: 69
entrySet: key: 70--- value: 70
entrySet: key: 71--- value: 71
entrySet: key: 72--- value: 72
entrySet: key: 73--- value: 73
entrySet: key: 74--- value: 74
entrySet: key: 75--- value: 75
entrySet: key: 76--- value: 76
entrySet: key: 77--- value: 77
entrySet: key: 78--- value: 78
entrySet: key: 79--- value: 79
entrySet: key: 80--- value: 80
entrySet: key: 81--- value: 81
entrySet: key: 82--- value: 82
entrySet: key: 83--- value: 83
entrySet: key: 84--- value: 84
entrySet: key: 85--- value: 85
entrySet: key: 86--- value: 86
entrySet: key: 87--- value: 87
entrySet: key: 88--- value: 88
entrySet: key: 89--- value: 89
entrySet: key: 90--- value: 90
entrySet: key: 91--- value: 91
entrySet: key: 92--- value: 92
entrySet: key: 93--- value: 93
entrySet: key: 94--- value: 94
entrySet: key: 95--- value: 95
entrySet: key: 96--- value: 96
entrySet: key: 97--- value: 97
entrySet: key: 98--- value: 98
entrySet: key: 99--- value: 99
entrySet forEach循环: key: 0--- value: 0
entrySet forEach循环: key: 1--- value: 1
entrySet forEach循环: key: 2--- value: 2
entrySet forEach循环: key: 3--- value: 3
entrySet forEach循环: key: 4--- value: 4
entrySet forEach循环: key: 5--- value: 5
entrySet forEach循环: key: 6--- value: 6
entrySet forEach循环: key: 7--- value: 7
entrySet forEach循环: key: 8--- value: 8
entrySet forEach循环: key: 9--- value: 9
entrySet forEach循环: key: 10--- value: 10
entrySet forEach循环: key: 11--- value: 11
entrySet forEach循环: key: 12--- value: 12
entrySet forEach循环: key: 13--- value: 13
entrySet forEach循环: key: 14--- value: 14
entrySet forEach循环: key: 15--- value: 15
entrySet forEach循环: key: 16--- value: 16
entrySet forEach循环: key: 17--- value: 17
entrySet forEach循环: key: 18--- value: 18
entrySet forEach循环: key: 19--- value: 19
entrySet forEach循环: key: 20--- value: 20
entrySet forEach循环: key: 21--- value: 21
entrySet forEach循环: key: 22--- value: 22
entrySet forEach循环: key: 23--- value: 23
entrySet forEach循环: key: 24--- value: 24
entrySet forEach循环: key: 25--- value: 25
entrySet forEach循环: key: 26--- value: 26
entrySet forEach循环: key: 27--- value: 27
entrySet forEach循环: key: 28--- value: 28
entrySet forEach循环: key: 29--- value: 29
entrySet forEach循环: key: 30--- value: 30
entrySet forEach循环: key: 31--- value: 31
entrySet forEach循环: key: 32--- value: 32
entrySet forEach循环: key: 33--- value: 33
entrySet forEach循环: key: 34--- value: 34
entrySet forEach循环: key: 35--- value: 35
entrySet forEach循环: key: 36--- value: 36
entrySet forEach循环: key: 37--- value: 37
entrySet forEach循环: key: 38--- value: 38
entrySet forEach循环: key: 39--- value: 39
entrySet forEach循环: key: 40--- value: 40
entrySet forEach循环: key: 41--- value: 41
entrySet forEach循环: key: 42--- value: 42
entrySet forEach循环: key: 43--- value: 43
entrySet forEach循环: key: 44--- value: 44
entrySet forEach循环: key: 45--- value: 45
entrySet forEach循环: key: 46--- value: 46
entrySet forEach循环: key: 47--- value: 47
entrySet forEach循环: key: 48--- value: 48
entrySet forEach循环: key: 49--- value: 49
entrySet forEach循环: key: 50--- value: 50
entrySet forEach循环: key: 51--- value: 51
entrySet forEach循环: key: 52--- value: 52
entrySet forEach循环: key: 53--- value: 53
entrySet forEach循环: key: 54--- value: 54
entrySet forEach循环: key: 55--- value: 55
entrySet forEach循环: key: 56--- value: 56
entrySet forEach循环: key: 57--- value: 57
entrySet forEach循环: key: 58--- value: 58
entrySet forEach循环: key: 59--- value: 59
entrySet forEach循环: key: 60--- value: 60
entrySet forEach循环: key: 61--- value: 61
entrySet forEach循环: key: 62--- value: 62
entrySet forEach循环: key: 63--- value: 63
entrySet forEach循环: key: 64--- value: 64
entrySet forEach循环: key: 65--- value: 65
entrySet forEach循环: key: 66--- value: 66
entrySet forEach循环: key: 67--- value: 67
entrySet forEach循环: key: 68--- value: 68
entrySet forEach循环: key: 69--- value: 69
entrySet forEach循环: key: 70--- value: 70
entrySet forEach循环: key: 71--- value: 71
entrySet forEach循环: key: 72--- value: 72
entrySet forEach循环: key: 73--- value: 73
entrySet forEach循环: key: 74--- value: 74
entrySet forEach循环: key: 75--- value: 75
entrySet forEach循环: key: 76--- value: 76
entrySet forEach循环: key: 77--- value: 77
entrySet forEach循环: key: 78--- value: 78
entrySet forEach循环: key: 79--- value: 79
entrySet forEach循环: key: 80--- value: 80
entrySet forEach循环: key: 81--- value: 81
entrySet forEach循环: key: 82--- value: 82
entrySet forEach循环: key: 83--- value: 83
entrySet forEach循环: key: 84--- value: 84
entrySet forEach循环: key: 85--- value: 85
entrySet forEach循环: key: 86--- value: 86
entrySet forEach循环: key: 87--- value: 87
entrySet forEach循环: key: 88--- value: 88
entrySet forEach循环: key: 89--- value: 89
entrySet forEach循环: key: 90--- value: 90
entrySet forEach循环: key: 91--- value: 91
entrySet forEach循环: key: 92--- value: 92
entrySet forEach循环: key: 93--- value: 93
entrySet forEach循环: key: 94--- value: 94
entrySet forEach循环: key: 95--- value: 95
entrySet forEach循环: key: 96--- value: 96
entrySet forEach循环: key: 97--- value: 97
entrySet forEach循环: key: 98--- value: 98
entrySet forEach循环: key: 99--- value: 99
keySet: key: 0--- value: 0
keySet: key: 1--- value: 1
keySet: key: 2--- value: 2
keySet: key: 3--- value: 3
keySet: key: 4--- value: 4
keySet: key: 5--- value: 5
keySet: key: 6--- value: 6
keySet: key: 7--- value: 7
keySet: key: 8--- value: 8
keySet: key: 9--- value: 9
keySet: key: 10--- value: 10
keySet: key: 11--- value: 11
keySet: key: 12--- value: 12
keySet: key: 13--- value: 13
keySet: key: 14--- value: 14
keySet: key: 15--- value: 15
keySet: key: 16--- value: 16
keySet: key: 17--- value: 17
keySet: key: 18--- value: 18
keySet: key: 19--- value: 19
keySet: key: 20--- value: 20
keySet: key: 21--- value: 21
keySet: key: 22--- value: 22
keySet: key: 23--- value: 23
keySet: key: 24--- value: 24
keySet: key: 25--- value: 25
keySet: key: 26--- value: 26
keySet: key: 27--- value: 27
keySet: key: 28--- value: 28
keySet: key: 29--- value: 29
keySet: key: 30--- value: 30
keySet: key: 31--- value: 31
keySet: key: 32--- value: 32
keySet: key: 33--- value: 33
keySet: key: 34--- value: 34
keySet: key: 35--- value: 35
keySet: key: 36--- value: 36
keySet: key: 37--- value: 37
keySet: key: 38--- value: 38
keySet: key: 39--- value: 39
keySet: key: 40--- value: 40
keySet: key: 41--- value: 41
keySet: key: 42--- value: 42
keySet: key: 43--- value: 43
keySet: key: 44--- value: 44
keySet: key: 45--- value: 45
keySet: key: 46--- value: 46
keySet: key: 47--- value: 47
keySet: key: 48--- value: 48
keySet: key: 49--- value: 49
keySet: key: 50--- value: 50
keySet: key: 51--- value: 51
keySet: key: 52--- value: 52
keySet: key: 53--- value: 53
keySet: key: 54--- value: 54
keySet: key: 55--- value: 55
keySet: key: 56--- value: 56
keySet: key: 57--- value: 57
keySet: key: 58--- value: 58
keySet: key: 59--- value: 59
keySet: key: 60--- value: 60
keySet: key: 61--- value: 61
keySet: key: 62--- value: 62
keySet: key: 63--- value: 63
keySet: key: 64--- value: 64
keySet: key: 65--- value: 65
keySet: key: 66--- value: 66
keySet: key: 67--- value: 67
keySet: key: 68--- value: 68
keySet: key: 69--- value: 69
keySet: key: 70--- value: 70
keySet: key: 71--- value: 71
keySet: key: 72--- value: 72
keySet: key: 73--- value: 73
keySet: key: 74--- value: 74
keySet: key: 75--- value: 75
keySet: key: 76--- value: 76
keySet: key: 77--- value: 77
keySet: key: 78--- value: 78
keySet: key: 79--- value: 79
keySet: key: 80--- value: 80
keySet: key: 81--- value: 81
keySet: key: 82--- value: 82
keySet: key: 83--- value: 83
keySet: key: 84--- value: 84
keySet: key: 85--- value: 85
keySet: key: 86--- value: 86
keySet: key: 87--- value: 87
keySet: key: 88--- value: 88
keySet: key: 89--- value: 89
keySet: key: 90--- value: 90
keySet: key: 91--- value: 91
keySet: key: 92--- value: 92
keySet: key: 93--- value: 93
keySet: key: 94--- value: 94
keySet: key: 95--- value: 95
keySet: key: 96--- value: 96
keySet: key: 97--- value: 97
keySet: key: 98--- value: 98
keySet: key: 99--- value: 99
keySet forEach循环: key: 0--- value: 0
keySet forEach循环: key: 1--- value: 1
keySet forEach循环: key: 2--- value: 2
keySet forEach循环: key: 3--- value: 3
keySet forEach循环: key: 4--- value: 4
keySet forEach循环: key: 5--- value: 5
keySet forEach循环: key: 6--- value: 6
keySet forEach循环: key: 7--- value: 7
keySet forEach循环: key: 8--- value: 8
keySet forEach循环: key: 9--- value: 9
keySet forEach循环: key: 10--- value: 10
keySet forEach循环: key: 11--- value: 11
keySet forEach循环: key: 12--- value: 12
keySet forEach循环: key: 13--- value: 13
keySet forEach循环: key: 14--- value: 14
keySet forEach循环: key: 15--- value: 15
keySet forEach循环: key: 16--- value: 16
keySet forEach循环: key: 17--- value: 17
keySet forEach循环: key: 18--- value: 18
keySet forEach循环: key: 19--- value: 19
keySet forEach循环: key: 20--- value: 20
keySet forEach循环: key: 21--- value: 21
keySet forEach循环: key: 22--- value: 22
keySet forEach循环: key: 23--- value: 23
keySet forEach循环: key: 24--- value: 24
keySet forEach循环: key: 25--- value: 25
keySet forEach循环: key: 26--- value: 26
keySet forEach循环: key: 27--- value: 27
keySet forEach循环: key: 28--- value: 28
keySet forEach循环: key: 29--- value: 29
keySet forEach循环: key: 30--- value: 30
keySet forEach循环: key: 31--- value: 31
keySet forEach循环: key: 32--- value: 32
keySet forEach循环: key: 33--- value: 33
keySet forEach循环: key: 34--- value: 34
keySet forEach循环: key: 35--- value: 35
keySet forEach循环: key: 36--- value: 36
keySet forEach循环: key: 37--- value: 37
keySet forEach循环: key: 38--- value: 38
keySet forEach循环: key: 39--- value: 39
keySet forEach循环: key: 40--- value: 40
keySet forEach循环: key: 41--- value: 41
keySet forEach循环: key: 42--- value: 42
keySet forEach循环: key: 43--- value: 43
keySet forEach循环: key: 44--- value: 44
keySet forEach循环: key: 45--- value: 45
keySet forEach循环: key: 46--- value: 46
keySet forEach循环: key: 47--- value: 47
keySet forEach循环: key: 48--- value: 48
keySet forEach循环: key: 49--- value: 49
keySet forEach循环: key: 50--- value: 50
keySet forEach循环: key: 51--- value: 51
keySet forEach循环: key: 52--- value: 52
keySet forEach循环: key: 53--- value: 53
keySet forEach循环: key: 54--- value: 54
keySet forEach循环: key: 55--- value: 55
keySet forEach循环: key: 56--- value: 56
keySet forEach循环: key: 57--- value: 57
keySet forEach循环: key: 58--- value: 58
keySet forEach循环: key: 59--- value: 59
keySet forEach循环: key: 60--- value: 60
keySet forEach循环: key: 61--- value: 61
keySet forEach循环: key: 62--- value: 62
keySet forEach循环: key: 63--- value: 63
keySet forEach循环: key: 64--- value: 64
keySet forEach循环: key: 65--- value: 65
keySet forEach循环: key: 66--- value: 66
keySet forEach循环: key: 67--- value: 67
keySet forEach循环: key: 68--- value: 68
keySet forEach循环: key: 69--- value: 69
keySet forEach循环: key: 70--- value: 70
keySet forEach循环: key: 71--- value: 71
keySet forEach循环: key: 72--- value: 72
keySet forEach循环: key: 73--- value: 73
keySet forEach循环: key: 74--- value: 74
keySet forEach循环: key: 75--- value: 75
keySet forEach循环: key: 76--- value: 76
keySet forEach循环: key: 77--- value: 77
keySet forEach循环: key: 78--- value: 78
keySet forEach循环: key: 79--- value: 79
keySet forEach循环: key: 80--- value: 80
keySet forEach循环: key: 81--- value: 81
keySet forEach循环: key: 82--- value: 82
keySet forEach循环: key: 83--- value: 83
keySet forEach循环: key: 84--- value: 84
keySet forEach循环: key: 85--- value: 85
keySet forEach循环: key: 86--- value: 86
keySet forEach循环: key: 87--- value: 87
keySet forEach循环: key: 88--- value: 88
keySet forEach循环: key: 89--- value: 89
keySet forEach循环: key: 90--- value: 90
keySet forEach循环: key: 91--- value: 91
keySet forEach循环: key: 92--- value: 92
keySet forEach循环: key: 93--- value: 93
keySet forEach循环: key: 94--- value: 94
keySet forEach循环: key: 95--- value: 95
keySet forEach循环: key: 96--- value: 96
keySet forEach循环: key: 97--- value: 97
keySet forEach循环: key: 98--- value: 98
keySet forEach循环: key: 99--- value: 99
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