Java集合的总结

transient Object[] elementData; // non-private to simplify nested class accessCopy to clipboardErrorCopied

private void readObject(java.io.ObjectInputStream s)
    throws java.io.IOException, ClassNotFoundException {
    elementData = EMPTY_ELEMENTDATA;

    // Read in size, and any hidden stuff
    s.defaultReadObject();

    // Read in capacity
    s.readInt(); // ignored

    if (size > 0) {
        // be like clone(), allocate array based upon size not capacity
        ensureCapacityInternal(size);

        Object[] a = elementData;
        // Read in all elements in the proper order.
        for (int i=0; i<size; i++) {
            a[i] = s.readObject();
        }
    }
}

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 size as capacity for behavioural compatibility with clone()
    s.writeInt(size);

    // 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();
    }
}Copy to clipboardErrorCopied

ArrayList list = new ArrayList();
ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream(file));
oos.writeObject(list);

public synchronized boolean add(E e) {
    modCount++;
    ensureCapacityHelper(elementCount + 1);
    elementData[elementCount++] = e;
    return true;
}

public synchronized E get(int index) {
    if (index >= elementCount)
        throw new ArrayIndexOutOfBoundsException(index);

    return elementData(index);
}Copy to clipboardErrorCopied

List<String> list = new ArrayList<>();
List<String> synList = Collections.synchronizedList(list);Copy to clipboardErrorCopied

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

final transient ReentrantLock lock = new ReentrantLock();

public void add(int index, E element) {
    final ReentrantLock lock = this.lock;
    lock.lock();
    try {
        Object[] elements = getArray();
        int len = elements.length;
        if (index > len || index < 0)
            throw new IndexOutOfBoundsException("Index: "+index+
                                                ", Size: "+len);
        Object[] newElements;
        int numMoved = len - index;
        if (numMoved == 0)
            newElements = Arrays.copyOf(elements, len + 1);
        else {
            newElements = new Object[len + 1];
            System.arraycopy(elements, 0, newElements, 0, index);
            System.arraycopy(elements, index, newElements, index + 1,
                             numMoved);
        }
        newElements[index] = element;
        setArray(newElements);
    } finally {
        lock.unlock();
    }
}

int hash = hash(key);
int i = indexFor(hash, table.length);

static final class HashEntry<K,V> {
    final int hash;
    final K key;
    volatile V value;
    volatile HashEntry<K,V> next;
}Copy to clipboardErrorCopied

static final class Segment<K,V> extends ReentrantLock implements Serializable {

    private static final long serialVersionUID = 2249069246763182397L;

    static final int MAX_SCAN_RETRIES =
        Runtime.getRuntime().availableProcessors() > 1 ? 64 : 1;

    transient volatile HashEntry<K,V>[] table;

    transient int count;

    transient int modCount;

    transient int threshold;

    final float loadFactor;
}Copy to clipboardErrorCopied

final Segment<K,V>[] segments;Copy to clipboardErrorCopied

static final int DEFAULT_CONCURRENCY_LEVEL = 16;Copy to clipboardErrorCopied

/**
 * The number of elements. Accessed only either within locks
 * or among other volatile reads that maintain visibility.
 */
transient int count;Copy to clipboardErrorCopied

/**
 * Number of unsynchronized retries in size and containsValue
 * methods before resorting to locking. This is used to avoid
 * unbounded retries if tables undergo continuous modification
 * which would make it impossible to obtain an accurate result.
 */
static final int RETRIES_BEFORE_LOCK = 2;

public int size() {
    // Try a few times to get accurate count. On failure due to
    // continuous async changes in table, resort to locking.
    final Segment<K,V>[] segments = this.segments;
    int size;
    boolean overflow; // true if size overflows 32 bits
    long sum;         // sum of modCounts
    long last = 0L;   // previous sum
    int retries = -1; // first iteration isn't retry
    try {
        for (;;) {
            // 超过尝试次数，则对每个 Segment 加锁
            if (retries++ == RETRIES_BEFORE_LOCK) {
                for (int j = 0; j < segments.length; ++j)
                    ensureSegment(j).lock(); // force creation
            }
            sum = 0L;
            size = 0;
            overflow = false;
            for (int j = 0; j < segments.length; ++j) {
                Segment<K,V> seg = segmentAt(segments, j);
                if (seg != null) {
                    sum += seg.modCount;
                    int c = seg.count;
                    if (c < 0 || (size += c) < 0)
                        overflow = true;
                }
            }
            // 连续两次得到的结果一致，则认为这个结果是正确的
            if (sum == last)
                break;
            last = sum;
        }
    } finally {
        if (retries > RETRIES_BEFORE_LOCK) {
            for (int j = 0; j < segments.length; ++j)
                segmentAt(segments, j).unlock();
        }
    }
    return overflow ? Integer.MAX_VALUE : size;
}

public class LinkedHashMap<K,V> extends HashMap<K,V> implements Map<K,V>Copy to clipboardErrorCopied

/**
 * The head (eldest) of the doubly linked list.
 */
transient LinkedHashMap.Entry<K,V> head;

/**
 * The tail (youngest) of the doubly linked list.
 */
transient LinkedHashMap.Entry<K,V> tail;Copy to clipboardErrorCopied

final boolean accessOrder;Copy to clipboardErrorCopied

void afterNodeAccess(Node<K,V> p) { }
void afterNodeInsertion(boolean evict) { }

void afterNodeAccess(Node<K,V> e) { // move node to last
    LinkedHashMap.Entry<K,V> last;
    if (accessOrder && (last = tail) != e) {
        LinkedHashMap.Entry<K,V> p =
            (LinkedHashMap.Entry<K,V>)e, b = p.before, a = p.after;
        p.after = null;
        if (b == null)
            head = a;
        else
            b.after = a;
        if (a != null)
            a.before = b;
        else
            last = b;
        if (last == null)
            head = p;
        else {
            p.before = last;
            last.after = p;
        }
        tail = p;
        ++modCount;
    }
}Copy to clipboardErrorCopied

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);
    }
}Copy to clipboardErrorCopied

protected boolean removeEldestEntry(Map.Entry<K,V> eldest) {
    return false;
}

package handlers;

import com.sun.org.apache.bcel.internal.generic.LUSHR;

import java.util.LinkedHashMap;
import java.util.Map;


class LRU<K,V> extends LinkedHashMap<K,V>{
    public final int max_entires;

    public LRU(int i){
        max_entires = i;
    }

    @Override
    protected boolean removeEldestEntry(Map.Entry<K, V> eldest) {
        return size() > max_entires;
    }



    public static void main(String[] args) {
        LRU lruCache = new LRU(5);
        lruCache.put(1,3);
        lruCache.put(2,5);
        lruCache.put(3,5);
        lruCache.put(4,77);
        lruCache.put(5,7);
        lruCache.put(6,5);
        lruCache.put(7,7);
        lruCache.put(8,5);
        lruCache.put(4,77);

        System.out.println(lruCache.get(7));
        System.out.println(lruCache.get(6));
        System.out.println(lruCache.get(4));
        System.out.println(lruCache.get(3));
    }

    }

private static class Entry<K,V> extends WeakReference<Object> implements Map.Entry<K,V>Copy to clipboardErrorCopied

public final class ConcurrentCache<K, V> {

    private final int size;

    private final Map<K, V> eden;

    private final Map<K, V> longterm;

    public ConcurrentCache(int size) {
        this.size = size;
        this.eden = new ConcurrentHashMap<>(size);
        this.longterm = new WeakHashMap<>(size);
    }

    public V get(K k) {
        V v = this.eden.get(k);
        if (v == null) {
            v = this.longterm.get(k);
            if (v != null)
                this.eden.put(k, v);
        }
        return v;
    }

    public void put(K k, V v) {
        if (this.eden.size() >= size) {
            this.longterm.putAll(this.eden);
            this.eden.clear();
        }
        this.eden.put(k, v);
    }
}