CS-Notes/notes/Java 容器.md

<!-- GFM-TOC -->
* [????](#????)
    * [1. List](#1-list)
    * [2. Set](#2-set)
    * [3. Queue](#3-queue)
    * [4. Map](#4-map)
    * [5. Java 1.0/1.1 ????](#5-java-1011-????)
* [?????<3F><>??????](#?????<3F><>??????)
    * [1. ????????](#1-????????)
    * [2. ????????](#2-????????)
* [???](#???)
* [??????](#??????)
    * [1. ArraList](#1-arralist)
    * [2. Vector ?? Stack](#2-vector-??-stack)
    * [3. LinkedList](#3-linkedlist)
    * [4. TreeMap](#4-treemap)
    * [5. HashMap](#5-hashmap)
    * [6. LinkedHashMap](#6-linkedhashmap)
    * [7. ConcurrentHashMap](#7-concurrenthashmap)
* [?<3F><>?????](#?<3F><>?????)
<!-- GFM-TOC -->

# ????

![](https://github.com/CyC2018/InterviewNotes/blob/master/pics/ebf03f56-f957-4435-9f8f-0f605661484d.jpg)

??????????? Collection ?? Map ?????Collection ??????? List??Set ??? Queue??

## 1. List

- ArrayList???????????????????????????

- LinkedList????????????????????????????????????????????????<3F><>????????????????????LinkedList ????????????????<3F><>??????<3F><>?

## 2. Set

- HashSet?????? Hash ???????????????????????????

- TreeSet????????????????????????????<3F><>????? HashSet??

- LinkedListHashSet?????? HashSet ?????<3F><>?????????????????????????????????????????

## 3. Queue

???????????LinkedList ?? PriorityQueue?????? LinkedList ????????<3F><>?PriorityQueue ???????????

## 4. Map

- HashMap?????? Hash ???

- LinkedHashMap??????????????????????????????????????????????LRU?????

- TreeMap?????????????

- ConcurrentHashMap??????? Map?????<3F>p?????? HashTable ?????????

## 5. Java 1.0/1.1 ????

??????????????????????????????????????????????

- Vector???? ArrayList ??????????????????

- HashTable???? HashMap ??????????????????

# ?????<3F><>??????

## 1. ????????

????????????????????????????? Iterator ??????????????????????????????????<3F><>?????

[Java ?<3F><>???????? ](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)

## 2. ????????

java.util.Arrays#asList() ????????????????? List ?????

```java
 List list = Arrays.asList(1, 2, 3);
 int[] arr = {1, 2, 3};
 list = Arrays.asList(arr);
```

# ???

??? hasCode() ??????????????????????????

?? equals() ???????<3F><>??????????????????????????????????????????????????????????????????????

??????????????????????

1. ?????
2. ?????
3. ??????
4. ????????<3F><>??? x.equals(y)?????????
5. ???<3F>ʦ<EFBFBD>??? null ????? x ???? x.equals(nul) ?????? false

# ??????

????????? [ ?? - ???? ](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) ????????????????????<3F><>???????

????????[OpenJDK 1.7](http://download.java.net/openjdk/jdk7)

## 1. ArraList

[ArraList.java](https://github.com/CyC2018/InterviewNotes/blob/master/notes/src/ArrayList.java)

????? RandomAccess ??????????????????????????????????? ArrayList ??????????????

```java
public class ArrayList<E> extends AbstractList<E>
    implements List<E>, RandomAccess, Cloneable, java.io.Serializable
```

??????????????????????????? transient ???<3F><>?????????????<3F><>???????<3F><>????????????????????????????????<3F><>????????<3F><> writeObject() ?? readObject()??

```java
private transient Object[] elementData;
```

?????????<3F><>? 10

```java
public ArrayList(int initialCapacity) {
    super();
    if (initialCapacity < 0)
        throw new IllegalArgumentException("Illegal Capacity: "+ initialCapacity);
    this.elementData = new Object[initialCapacity];
}

public ArrayList() {
    this(10);
}
```

??????????? System.arraycopy() ???????<3F><>?????????????????????????????????????????????<3F><>????????????????<3F><>?????

```java
public E remove(int index) {
    rangeCheck(index);

    modCount++;
    E oldValue = elementData(index);

    int numMoved = size - index - 1;
    if (numMoved > 0)
        System.arraycopy(elementData, index+1, elementData, index, numMoved);
    elementData[--size] = null; // Let gc do its work

    return oldValue;
}
```

?????????? ensureCapacity() ????????????????????????????????????????????????????????? 1.5 ????

modCount ??????? ArrayList ?????<3F><>?????????????????? add() ?? addAll() ?????????? ensureCapacity()?????????? ensureCapacity() ?<3F><>? modCount ????????

```java
public void ensureCapacity(int minCapacity) {
    if (minCapacity > 0)
        ensureCapacityInternal(minCapacity);
}

private void ensureCapacityInternal(int minCapacity) {
    modCount++;
    // overflow-conscious code
    if (minCapacity - elementData.length > 0)
        grow(minCapacity);
}

private static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8;

private void grow(int minCapacity) {
    // overflow-conscious code
    int oldCapacity = elementData.length;
    int newCapacity = oldCapacity + (oldCapacity >> 1);
    if (newCapacity - minCapacity < 0)
        newCapacity = minCapacity;
    if (newCapacity - MAX_ARRAY_SIZE > 0)
        newCapacity = hugeCapacity(minCapacity);
    // minCapacity is usually close to size, so this is a win:
    elementData = Arrays.copyOf(elementData, newCapacity);
}

private static int hugeCapacity(int minCapacity) {
    if (minCapacity < 0) // overflow
        throw new OutOfMemoryError();
    return (minCapacity > MAX_ARRAY_SIZE) ?
        Integer.MAX_VALUE :
        MAX_ARRAY_SIZE;
}
```

????????<3F><>???????????????????????????? modCount ??????????????????? ConcurrentModificationException??

```java
private void writeObject(java.io.ObjectOutputStream s)
    throws java.io.IOException{
    // Write out element count, and any hidden stuff
    int expectedModCount = modCount;
    s.defaultWriteObject();

    // Write out array length
    s.writeInt(elementData.length);

    // Write out all elements in the proper order.
    for (int i=0; i<size; i++)
        s.writeObject(elementData[i]);

    if (modCount != expectedModCount) {
        throw new ConcurrentModificationException();
    }

}
```

**?? Vector ??????**

1.  Vector ?? ArrayList ???????????????<3F><>??????????? Vector ????????????????? ArrayList ????????????????? ArrayList ?????? Vector???????????????????????????????
2.  Vector ??????????????<3F><>?? 2 ??????? ArrayList ?? 1.5 ????

????????????? ArrayList????????? Collections.synchronizedList(new ArrayList<>()); ?????????????? ArrayList?????????? concurrent ????????? CopyOnWriteArrayList ??

**?? LinkedList ??????**

1.  ArrayList ??????????????LinkedList ??????????????????
2. ArrayList ???????????LinkedList ??????
3. LinkedList ??????<3F><>??????????????

## 2. Vector ?? Stack

[Vector.java](https://github.com/CyC2018/InterviewNotes/blob/master/notes/src/Vector.java)

## 3. LinkedList

[LinkedList.java](https://github.com/CyC2018/InterviewNotes/blob/master/notes/src/LinkedList.java)

## 4. TreeMap

[TreeMap.java](https://github.com/CyC2018/InterviewNotes/blob/master/notes/src/TreeMap.java)

## 5. HashMap

[HashMap.java](https://github.com/CyC2018/InterviewNotes/blob/master/notes/src/HashMap.java)

???????????????????

??????? capacity ? 16????????????????????? 2 ??<3F><>??????????? Entry[] table ?????????size ?????????????????

threshold ?<3F><>????? size ????????size ????<3F><>?? threshold??????????????????????????????

threshold = capacity * load_factor?????? load_factor ? table ????????????????load_factor ????????????????????????????<3F><>????????????

```java
static final int DEFAULT_INITIAL_CAPACITY = 16;

static final int MAXIMUM_CAPACITY = 1 << 30;

static final float DEFAULT_LOAD_FACTOR = 0.75f;

transient Entry[] table;

transient int size;

int threshold;

final float loadFactor;

transient int modCount;
```

?????????????????<3F><>?????????????????????? capacity ????????????

```java
void addEntry(int hash, K key, V value, int bucketIndex) {
    Entry<K,V> e = table[bucketIndex];
    table[bucketIndex] = new Entry<>(hash, key, value, e);
    if (size++ >= threshold)
        resize(2 * table.length);
}
```

Entry ??????????????????????<3F><>? next ????????<3F><>??????<3F><>?

```java
static class Entry<K,V> implements Map.Entry<K,V> {
    final K key;
    V value;
    Entry<K,V> next;
    final int hash;
}
```

get() ???????????????????key ? null ?? ??? null?????<3F><>?????? HashMap ??????? null ???????

```java
public V get(Object key) {
    if (key == null)
        return getForNullKey();
    int hash = hash(key.hashCode());
    for (Entry<K,V> e = table[indexFor(hash, table.length)]; e != null; e = e.next) {
        Object k;
        if (e.hash == hash && ((k = e.key) == key || key.equals(k)))
            return e.value;
    }
    return null;
}
```

put() ???????????? key ???? null ????????????????????????????? key ? null ??????????????? key ? null ???????????????????? 0 <20><>?????????? null ??????? hash ??????????????<3F><>?????????????

```java
public V put(K key, V value) {
    if (key == null)
        return putForNullKey(value);
    int hash = hash(key.hashCode());
    int i = indexFor(hash, table.length);
    for (Entry<K,V> e = table[i]; e != null; e = e.next) {
        Object k;
        if (e.hash == hash && ((k = e.key) == key || key.equals(k))) {
            V oldValue = e.value;
            e.value = value;
            e.recordAccess(this);
            return oldValue;
        }
    }

    modCount++;
    addEntry(hash, key, value, i);
    return null;
}
```

```java
private V putForNullKey(V value) {
    for (Entry<K,V> e = table[0]; e != null; e = e.next) {
        if (e.key == null) {
            V oldValue = e.value;
            e.value = value;
            e.recordAccess(this);
            return oldValue;
        }
    }
    modCount++;
    addEntry(0, null, value, 0);
    return null;
}
```

## 6. LinkedHashMap

[LinkedHashMap.java](https://github.com/CyC2018/InterviewNotes/blob/master/notes/src/HashMap.java)

## 7. ConcurrentHashMap

[ConcurrentHashMap.java](https://github.com/CyC2018/InterviewNotes/blob/master/notes/src/HashMap.java)

[ ??? ConcurrentHashMap ?????????????? ](https://www.ibm.com/developerworks/cn/java/java-lo-concurrenthashmap/)

# ?<3F><>?????

- Java ??????