362 lines
9.7 KiB
Markdown
362 lines
9.7 KiB
Markdown
<!-- GFM-TOC -->
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* [????](#????)
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* [1. List](#1-list)
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* [2. Set](#2-set)
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* [3. Queue](#3-queue)
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* [4. Map](#4-map)
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* [5. Java 1.0/1.1 ????](#5-java-1011-????)
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* [?????§Ö??????](#?????§Ö??????)
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* [1. ????????](#1-????????)
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* [2. ????????](#2-????????)
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* [???](#???)
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* [??????](#??????)
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* [1. ArraList](#1-arralist)
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* [2. Vector ?? Stack](#2-vector-??-stack)
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* [3. LinkedList](#3-linkedlist)
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* [4. TreeMap](#4-treemap)
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* [5. HashMap](#5-hashmap)
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* [6. LinkedHashMap](#6-linkedhashmap)
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* [7. ConcurrentHashMap](#7-concurrenthashmap)
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* [?¦Ï?????](#?¦Ï?????)
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<!-- GFM-TOC -->
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# ????
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??????????? Collection ?? Map ?????Collection ??????? List??Set ??? Queue??
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## 1. List
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- ArrayList???????????????????????????
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- LinkedList????????????????????????????????????????????????§Þ????????????????????LinkedList ????????????????§Ü??????§³?
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## 2. Set
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- HashSet?????? Hash ???????????????????????????
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- TreeSet????????????????????????????§¹????? HashSet??
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- LinkedListHashSet?????? HashSet ?????§¹?????????????????????????????????????????
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## 3. Queue
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???????????LinkedList ?? PriorityQueue?????? LinkedList ????????§µ?PriorityQueue ???????????
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## 4. Map
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- HashMap?????? Hash ???
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- LinkedHashMap??????????????????????????????????????????????LRU?????
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- TreeMap?????????????
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- ConcurrentHashMap??????? Map?????<3F>p?????? HashTable ?????????
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## 5. Java 1.0/1.1 ????
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??????????????????????????????????????????????
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- Vector???? ArrayList ??????????????????
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- HashTable???? HashMap ??????????????????
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# ?????§Ö??????
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## 1. ????????
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????????????????????????????? Iterator ??????????????????????????????????§Ö?????
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[Java ?§Ö???????? ](https://github.com/CyC2018/InterviewNotes/blob/master/notes/%E8%AE%BE%E8%AE%A1%E6%A8%A1%E5%BC%8F.md#92-java-%E5%86%85%E7%BD%AE%E7%9A%84%E8%BF%AD%E4%BB%A3%E5%99%A8)
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## 2. ????????
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java.util.Arrays#asList() ????????????????? List ?????
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```java
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List list = Arrays.asList(1, 2, 3);
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int[] arr = {1, 2, 3};
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list = Arrays.asList(arr);
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```
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# ???
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??? hasCode() ??????????????????????????
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?? equals() ???????§Ø??????????????????????????????????????????????????????????????????????
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??????????????????????
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1. ?????
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2. ?????
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3. ??????
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4. ????????¦Å??? x.equals(y)?????????
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5. ???¦Ê¦Â??? null ????? x ???? x.equals(nul) ?????? false
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# ??????
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????????? [ ?? - ???? ](https://github.com/CyC2018/InterviewNotes/blob/master/notes/%E7%AE%97%E6%B3%95.md#%E7%AC%AC%E4%B8%89%E7%AB%A0-%E6%9F%A5%E6%89%BE) ????????????????????§Ü???????
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????????[OpenJDK 1.7](http://download.java.net/openjdk/jdk7)
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## 1. ArraList
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[ArraList.java](https://github.com/CyC2018/InterviewNotes/blob/master/notes/src/ArrayList.java)
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????? RandomAccess ??????????????????????????????????? ArrayList ??????????????
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```java
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public class ArrayList<E> extends AbstractList<E>
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implements List<E>, RandomAccess, Cloneable, java.io.Serializable
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```
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??????????????????????????? transient ???¦²?????????????öö???????¦Ë????????????????????????????????§Ý????????§Õ writeObject() ?? readObject()??
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```java
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private transient Object[] elementData;
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```
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?????????§³? 10
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```java
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public ArrayList(int initialCapacity) {
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super();
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if (initialCapacity < 0)
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throw new IllegalArgumentException("Illegal Capacity: "+ initialCapacity);
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this.elementData = new Object[initialCapacity];
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}
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public ArrayList() {
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this(10);
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}
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```
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??????????? System.arraycopy() ???????§Ú?????????????????????????????????????????????§³????????????????§Õ?????
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```java
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public E remove(int index) {
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rangeCheck(index);
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modCount++;
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E oldValue = elementData(index);
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int numMoved = size - index - 1;
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if (numMoved > 0)
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System.arraycopy(elementData, index+1, elementData, index, numMoved);
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elementData[--size] = null; // Let gc do its work
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return oldValue;
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}
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```
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?????????? ensureCapacity() ????????????????????????????????????????????????????????? 1.5 ????
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modCount ??????? ArrayList ?????<3F>£?????????????????? add() ?? addAll() ?????????? ensureCapacity()?????????? ensureCapacity() ?§Ø? modCount ????????
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```java
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public void ensureCapacity(int minCapacity) {
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if (minCapacity > 0)
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ensureCapacityInternal(minCapacity);
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}
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private void ensureCapacityInternal(int minCapacity) {
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modCount++;
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// overflow-conscious code
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if (minCapacity - elementData.length > 0)
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grow(minCapacity);
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}
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private static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8;
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private void grow(int minCapacity) {
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// overflow-conscious code
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int oldCapacity = elementData.length;
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int newCapacity = oldCapacity + (oldCapacity >> 1);
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if (newCapacity - minCapacity < 0)
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newCapacity = minCapacity;
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if (newCapacity - MAX_ARRAY_SIZE > 0)
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newCapacity = hugeCapacity(minCapacity);
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// minCapacity is usually close to size, so this is a win:
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elementData = Arrays.copyOf(elementData, newCapacity);
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}
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private static int hugeCapacity(int minCapacity) {
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if (minCapacity < 0) // overflow
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throw new OutOfMemoryError();
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return (minCapacity > MAX_ARRAY_SIZE) ?
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Integer.MAX_VALUE :
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MAX_ARRAY_SIZE;
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}
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```
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????????§Ý???????????????????????????? modCount ??????????????????? ConcurrentModificationException??
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```java
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private void writeObject(java.io.ObjectOutputStream s)
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throws java.io.IOException{
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// Write out element count, and any hidden stuff
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int expectedModCount = modCount;
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s.defaultWriteObject();
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// Write out array length
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s.writeInt(elementData.length);
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// Write out all elements in the proper order.
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for (int i=0; i<size; i++)
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s.writeObject(elementData[i]);
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if (modCount != expectedModCount) {
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throw new ConcurrentModificationException();
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}
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}
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```
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**?? Vector ??????**
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1. Vector ?? ArrayList ???????????????¦·??????????? Vector ????????????????? ArrayList ????????????????? ArrayList ?????? Vector???????????????????????????????
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2. Vector ??????????????§³?? 2 ??????? ArrayList ?? 1.5 ????
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????????????? ArrayList????????? Collections.synchronizedList(new ArrayList<>()); ?????????????? ArrayList?????????? concurrent ????????? CopyOnWriteArrayList ??
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**?? LinkedList ??????**
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1. ArrayList ??????????????LinkedList ??????????????????
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2. ArrayList ???????????LinkedList ??????
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3. LinkedList ??????¦Ë??????????????
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## 2. Vector ?? Stack
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[Vector.java](https://github.com/CyC2018/InterviewNotes/blob/master/notes/src/Vector.java)
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## 3. LinkedList
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[LinkedList.java](https://github.com/CyC2018/InterviewNotes/blob/master/notes/src/LinkedList.java)
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## 4. TreeMap
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[TreeMap.java](https://github.com/CyC2018/InterviewNotes/blob/master/notes/src/TreeMap.java)
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## 5. HashMap
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[HashMap.java](https://github.com/CyC2018/InterviewNotes/blob/master/notes/src/HashMap.java)
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???????????????????
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??????? capacity ? 16????????????????????? 2 ??¦Ç??????????? Entry[] table ?????????size ?????????????????
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threshold ?ÕÇ????? size ????????size ????§³?? threshold??????????????????????????????
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threshold = capacity * load_factor?????? load_factor ? table ????????????????load_factor ????????????????????????????§¹????????????
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```java
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static final int DEFAULT_INITIAL_CAPACITY = 16;
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static final int MAXIMUM_CAPACITY = 1 << 30;
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static final float DEFAULT_LOAD_FACTOR = 0.75f;
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transient Entry[] table;
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transient int size;
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int threshold;
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final float loadFactor;
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transient int modCount;
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```
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?????????????????§á?????????????????????? capacity ????????????
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```java
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void addEntry(int hash, K key, V value, int bucketIndex) {
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Entry<K,V> e = table[bucketIndex];
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table[bucketIndex] = new Entry<>(hash, key, value, e);
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if (size++ >= threshold)
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resize(2 * table.length);
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}
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```
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Entry ??????????????????????§Ö? next ????????§Ý??????¨¢?
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```java
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static class Entry<K,V> implements Map.Entry<K,V> {
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final K key;
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V value;
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Entry<K,V> next;
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final int hash;
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}
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```
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get() ???????????????????key ? null ?? ??? null?????§á?????? HashMap ??????? null ???????
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```java
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public V get(Object key) {
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if (key == null)
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return getForNullKey();
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int hash = hash(key.hashCode());
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for (Entry<K,V> e = table[indexFor(hash, table.length)]; e != null; e = e.next) {
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Object k;
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if (e.hash == hash && ((k = e.key) == key || key.equals(k)))
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return e.value;
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}
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return null;
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}
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```
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put() ???????????? key ???? null ????????????????????????????? key ? null ??????????????? key ? null ???????????????????? 0 ¦Ë?????????? null ??????? hash ??????????????¡Â?????????????
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```java
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public V put(K key, V value) {
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if (key == null)
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return putForNullKey(value);
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int hash = hash(key.hashCode());
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int i = indexFor(hash, table.length);
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for (Entry<K,V> e = table[i]; e != null; e = e.next) {
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Object k;
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if (e.hash == hash && ((k = e.key) == key || key.equals(k))) {
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V oldValue = e.value;
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e.value = value;
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e.recordAccess(this);
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return oldValue;
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}
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}
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modCount++;
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addEntry(hash, key, value, i);
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return null;
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}
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```
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```java
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private V putForNullKey(V value) {
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for (Entry<K,V> e = table[0]; e != null; e = e.next) {
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if (e.key == null) {
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V oldValue = e.value;
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e.value = value;
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e.recordAccess(this);
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return oldValue;
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}
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}
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modCount++;
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addEntry(0, null, value, 0);
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return null;
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}
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```
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## 6. LinkedHashMap
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[LinkedHashMap.java](https://github.com/CyC2018/InterviewNotes/blob/master/notes/src/HashMap.java)
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## 7. ConcurrentHashMap
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[ConcurrentHashMap.java](https://github.com/CyC2018/InterviewNotes/blob/master/notes/src/HashMap.java)
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[ ??? ConcurrentHashMap ?????????????? ](https://www.ibm.com/developerworks/cn/java/java-lo-concurrenthashmap/)
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# ?¦Ï?????
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- Java ??????
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