CS-Notes/notes/Java 容器.md

• ????
  • 1. List
  • 2. Set
  • 3. Queue
  • 4. Map
  • 5. Java 1.0/1.1 ????
• ?????§Ö??????
  • 1. ????????
  • 2. ????????
• ???
• ??????
  • 1. ArraList
  • 2. Vector ?? Stack
  • 3. LinkedList
  • 4. TreeMap
  • 5. HashMap
  • 6. LinkedHashMap
  • 7. ConcurrentHashMap
• ?¦Ï?????

????

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

1. List

• ArrayList???????????????????????????

• LinkedList????????????????????????????????????????????????§Þ????????????????????LinkedList ????????????????§Ü??????§³?

2. Set

• HashSet?????? Hash ???????????????????????????

• TreeSet????????????????????????????§¹????? HashSet??

• LinkedListHashSet?????? HashSet ?????§¹?????????????????????????????????????????

3. Queue

???????????LinkedList ?? PriorityQueue?????? LinkedList ????????§µ?PriorityQueue ???????????

4. Map

• HashMap?????? Hash ???

• LinkedHashMap??????????????????????????????????????????????LRU?????

• TreeMap?????????????

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

5. Java 1.0/1.1 ????

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

• Vector???? ArrayList ??????????????????

• HashTable???? HashMap ??????????????????

?????§Ö??????

1. ????????

????????????????????????????? Iterator ??????????????????????????????????§Ö?????

Java ?§Ö????????

2. ????????

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

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

???

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

?? equals() ???????§Ø??????????????????????????????????????????????????????????????????????

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

1. ?????
2. ?????
3. ??????
4. ????????¦Å??? x.equals(y)?????????
5. ???¦Ê¦Â??? null ????? x ???? x.equals(nul) ?????? false

??????

????????? ?? - ???? ????????????????????§Ü???????

????????OpenJDK 1.7

1. ArraList

ArraList.java

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

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

??????????????????????????? transient ???¦²?????????????öö???????¦Ë????????????????????????????????§Ý????????§Õ writeObject() ?? readObject()??

private transient Object[] elementData;

?????????§³? 10

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() ???????§Ú?????????????????????????????????????????????§³????????????????§Õ?????

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() ?§Ø? modCount ????????

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;
}

????????§Ý???????????????????????????? modCount ??????????????????? ConcurrentModificationException??

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 ???????????????¦·??????????? Vector ????????????????? ArrayList ????????????????? ArrayList ?????? Vector???????????????????????????????
2. Vector ??????????????§³?? 2 ??????? ArrayList ?? 1.5 ????

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

?? LinkedList ??????

1. ArrayList ??????????????LinkedList ??????????????????
2. ArrayList ???????????LinkedList ??????
3. LinkedList ??????¦Ë??????????????

2. Vector ?? Stack

Vector.java

3. LinkedList

LinkedList.java

4. TreeMap

TreeMap.java

5. HashMap

HashMap.java

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

??????? capacity ? 16????????????????????? 2 ??¦Ç??????????? Entry[] table ?????????size ?????????????????

threshold ?ÕÇ????? size ????????size ????§³?? threshold??????????????????????????????

threshold = capacity * load_factor?????? load_factor ? table ????????????????load_factor ????????????????????????????§¹????????????

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;

?????????????????§á?????????????????????? capacity ????????????

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 ??????????????????????§Ö? next ????????§Ý??????¨¢?

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?????§á?????? HashMap ??????? null ???????

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 ¦Ë?????????? null ??????? hash ??????????????¡Â?????????????

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;
}

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

7. ConcurrentHashMap

ConcurrentHashMap.java

??? ConcurrentHashMap ??????????????

?¦Ï?????

• Java ??????