目錄
- @SuppressWarnings
- Spliterator
- Fail-Fast
- 序列化
- Consumer
- Vector刨析
- ArrayList刨析
- Stack刨析
總結：Java的Stack嚴格意義來說并不能說是Stack，因為它通過直接繼承Vector類，繼承了Vector所有的公有方法，它是一個擁有所有Vector容器方法的堆疊！
@SuppressWarnings
該批注的作用是給編譯器一條指令，告訴它對被批注的代碼元素內部的某些警告保持靜默，
| all | 抑制所有警告 |
|---|---|
| boxing | 抑制裝箱、拆箱操作時候的警告 |
| cast | 抑制映射相關的警告 |
| dep-ann | 抑制啟用注釋的警告 |
| deprecation | 抑制過期方法警告 |
| fallthrough | 抑制確在switch中缺失breaks的警告 |
| finally | 抑制finally模塊沒有回傳的警告 |
| hiding | to suppress warnings relative to locals that hide variable |
| incomplete-switch | 忽略沒有完整的switch陳述句的警告 |
| nls | 忽略非nls格式的字符的警告 |
| null | 忽略對null的操作的警告 |
| rawtypes | 使用generics時忽略沒有指定相應的型別的警告 |
| restriction | restriction to suppress warnings relative to usage of discouraged or forbidden references |
| serial | 忽略在serializable類中沒有宣告serialVersionUID變數的警告 |
| static-access | 抑制不正確的靜態訪問方式警告 |
| synthetic-access | 抑制子類沒有按最優方法訪問內部類的警告 |
| unchecked | 抑制沒有進行型別檢查操作的警告 |
| unqualified-field-access | 抑制沒有權限訪問的域的警告 |
| unused | 抑制沒被使用過的代碼的警告 |
Spliterator
Spliterator是Java 8中加入的一個新介面；這個名字代表“可拆分迭代器”（splitable iterator），和Iterator一樣，Spliterator也用于遍歷資料源中的元素，但它是為了并行執行而設計的，Java 8已經為集合框架中包含的所有資料結構提供了一個默認的Spliterator實作，
Fail-Fast
fail-fast 機制，即快速失敗機制，是java集合(Collection)中的一種錯誤檢測機制，當在迭代集合的程序中該集合在結構上發生改變的時候，就有可能會發生fail-fast，即拋出 ConcurrentModificationException例外，fail-fast機制并不保證在不同步的修改下一定會拋出例外，它只是盡最大努力去拋出，所以這種機制一般僅用于檢測bug，
在Vector中依賴modCount實作，一旦modCount發生變化，那么就觸發例外，
序列化
Java 提供了一種物件序列化的機制，該機制中，一個物件可以被表示為一個位元組序列，該位元組序列包括該物件的資料、有關物件的型別的資訊和存盤在物件中資料的型別，
將序列化物件寫入檔案之后，可以從檔案中讀取出來，并且對它進行反序列化，也就是說，物件的型別資訊、物件的資料，還有物件中的資料型別可以用來在記憶體中新建物件，
Consumer
函式式編程介面
@FunctionalInterface
public interface Consumer<T> {
/**
* Performs this operation on the given argument.
*
* @param t the input argument
*/
void accept(T t);
/**
* Returns a composed {@code Consumer} that performs, in sequence, this
* operation followed by the {@code after} operation. If performing either
* operation throws an exception, it is relayed to the caller of the
* composed operation. If performing this operation throws an exception,
* the {@code after} operation will not be performed.
*
* @param after the operation to perform after this operation
* @return a composed {@code Consumer} that performs in sequence this
* operation followed by the {@code after} operation
* @throws NullPointerException if {@code after} is null
*/
default Consumer<T> andThen(Consumer<? super T> after) {
Objects.requireNonNull(after);
return (T t) -> { accept(t); after.accept(t); };
}
}
Vector刨析
public class Vector<E>
extends AbstractList<E>
implements List<E>, RandomAccess, Cloneable, java.io.Serializable
{
//一個確保足夠大的陣列緩沖區
@SuppressWarnings("serial") // Conditionally serializable
protected Object[] elementData;
//記錄陣列緩沖區中實際存入的元素數量
protected int elementCount;
//vector容器建議自增的大小
protected int capacityIncrement;
/** use serialVersionUID from JDK 1.0.2 for interoperability */
@java.io.Serial
private static final long serialVersionUID = -2767605614048989439L;
public Vector(int initialCapacity, int capacityIncrement) {
super();
if (initialCapacity < 0)
throw new IllegalArgumentException("Illegal Capacity: "+
initialCapacity);
//首次Vector初始化
this.elementData = https://www.cnblogs.com/angelMask/p/new Object[initialCapacity];
//設定下次Vector容量的增加數量
this.capacityIncrement = capacityIncrement;
}
public Vector(int initialCapacity) {
//若capacityIncrement為空，則默認設定為0，即不會擴大容量
this(initialCapacity, 0);
}
public Vector() {
//默認Vector僅能存盤十個元素,且不會容量不會擴大!
this(10);
}
//Collection物件賦值給Vector的兩種情況
public Vector(Collection<? extends E> c) {
Object[] a = c.toArray();
elementCount = a.length;
//如果c的類物件是ArrayList的話，那么就可以直接賦值
if (c.getClass() == ArrayList.class) {
elementData = a;
} else {
//elementDate賦值為Object[]
elementData = Arrays.copyOf(a, elementCount, Object[].class);
}
}
/*
arraycopy(src, srcPos, dest, destPos, length)
1. src: 源陣列
2. srcPos: 源陣列的起點下標
3. dest: 目標陣列
4. destPos: 目標陣列的起點下標
5. length: 復制源陣列的元素個數
*/
//拷貝vector
public synchronized void copyInto(Object[] anArray) {
System.arraycopy(elementData, 0, anArray, 0, elementCount);
}
//修剪vector
public synchronized void trimToSize() {
modCount++;
int oldCapacity = elementData.length;
//如果陣列的大小大于陣列中元素的個數，則將陣列容量縮小為元素個數的容量
if (elementCount < oldCapacity) {
elementData = Arrays.copyOf(elementData, elementCount);
}
}
/**
* modCount定義在AbstractList中，用于記錄當前集合嘗試改變容量的次數
* 設定容器的最小容量
*/
public synchronized void ensureCapacity(int minCapacity) {
if (minCapacity > 0) {
modCount++;
if (minCapacity > elementData.length)
grow(minCapacity);
}
}
/**
* ArraysSupport.newLength(oldLength, minGrowth, prefGrowth)
* newLength函式中定義了取oldLength + max(minGrowth, prefGrowth)
* 即grow函式最小也會增長minGrowth, 最大則增加prefGrowth
* 也就是說一旦呼叫了grow()函式，那么增加的容量并不是設定的minCapacity而是經過的 * 計算的容量
*/
private Object[] grow(int minCapacity) {
int oldCapacity = elementData.length;
int newCapacity = ArraysSupport.newLength(oldCapacity,
minCapacity - oldCapacity, //minGrow
capacityIncrement > 0 ? capacityIncrement : oldCapacity//preGrow
);
return elementData = Arrays.copyOf(elementData, newCapacity);
}
//默認自增1
private Object[] grow() {
return grow(elementCount + 1);
}
//設定vector大小
//第一種情況，若vector的元素數量小于newSize那么直接擴大容量
//第二種情況，若vector的元素數量大于newSize那么就將多余的部分置為null，但是不修 //改vector本身的容量
public synchronized void setSize(int newSize) {
modCount++;
if (newSize > elementData.length)
grow(newSize);
final Object[] es = elementData;
for (int to = elementCount, i = newSize; i < to; i++)
es[i] = null;
elementCount = newSize;
}
//定義容量=容器大小
public synchronized int capacity() {
return elementData.length;
}
//定義大小=元素數量
public synchronized int size() {
return elementCount;
}
//判空
public synchronized boolean isEmpty() {
return elementCount == 0;
}
//獲取列舉物件
public Enumeration elements() {
return new Enumeration() {
//自定義列舉介面
int count = 0;
//提供給外部回圈使用的
public boolean hasMoreElements() {
return count < elementCount;
}
//拿到當前元素的值，并將列舉指向下一個
public E nextElement() {
synchronized (Vector.this) {
if (count < elementCount) {
return elementData(count++);
}
}
throw new NoSuchElementException("Vector Enumeration");
}
};
}
//indexOf(Object, x)找到Object則回傳下標，反之，回傳-1
public boolean contains(Object o) {
return indexOf(o, 0) >= 0;
}
//從零開始找目標Object
public int indexOf(Object o) {
return indexOf(o, 0);
}
//應該很好理解，為什么需要將NULL物件和Object物件區分？為什么需要使用equals()?
//equals()中的物件不能為null, ==判別的是地址是否相同而非大小
public synchronized int indexOf(Object o, int index) {
if (o == null) {
for (int i = index ; i < elementCount ; i++)
if (elementData[i]==null)
return i;
} else {
for (int i = index ; i < elementCount ; i++)
if (o.equals(elementData[i]))
return i;
}
return -1;
}
//Object最后一次出現的下標
public synchronized int lastIndexOf(Object o) {
return lastIndexOf(o, elementCount-1);
}
public synchronized int lastIndexOf(Object o, int index) {
if (index >= elementCount)
throw new IndexOutOfBoundsException(index + " >= "+ elementCount);
if (o == null) {
for (int i = index; i >= 0; i--)
if (elementData[i]==null)
return i;
} else {
for (int i = index; i >= 0; i--)
if (o.equals(elementData[i]))
return i;
}
return -1;
}
//獲取下標元素
public synchronized E elementAt(int index) {
if (index >= elementCount) {
throw new ArrayIndexOutOfBoundsException(index + " >= " + elementCount);
}
return elementData(index);
}
//獲取首位元素
public synchronized E firstElement() {
if (elementCount == 0) {
throw new NoSuchElementException();
}
return elementData(0);
}
//獲取最后一位元素
public synchronized E lastElement() {
if (elementCount == 0) {
throw new NoSuchElementException();
}
return elementData(elementCount - 1);
}
//為特定下標設定元素
public synchronized void setElementAt(E obj, int index) {
if (index >= elementCount) {
throw new ArrayIndexOutOfBoundsException(index + " >= " +
elementCount);
}
elementData[index] = obj;
}
//移除特定下標的元素
public synchronized void removeElementAt(int index) {
if (index >= elementCount) {
throw new ArrayIndexOutOfBoundsException(index + " >= " +
elementCount);
}
else if (index < 0) {
throw new ArrayIndexOutOfBoundsException(index);
}
int j = elementCount - index - 1;
//拷貝elementData的index+1處往后的元素至elementData的index處往后的元素
if (j > 0) {
System.arraycopy(elementData, index + 1, elementData, index, j);
}
modCount++;
elementCount--;
elementData[elementCount] = null; /* 為了讓GC回收null元素 */
}
//在特定下標插入元素
public synchronized void insertElementAt(E obj, int index) {
if (index > elementCount) {
throw new ArrayIndexOutOfBoundsException(index
+ " > " + elementCount);
}
modCount++;
final int s = elementCount;
Object[] elementData = https://www.cnblogs.com/angelMask/p/this.elementData;
//如果容量和元素數量相等，就擴容1
if (s == elementData.length)
elementData = grow();
//拷貝elementData的index往后的元素至elementData的index+1往后的元素
System.arraycopy(elementData, index,
elementData, index + 1,
s - index);
elementData[index] = obj;
elementCount = s + 1;
}
//在vector尾部增加元素
public synchronized void addElement(E obj) {
modCount++;
add(obj, elementData, elementCount);
}
//洗掉特定的元素->先找下標位置->洗掉特定下標的元素
public synchronized boolean removeElement(Object obj) {
modCount++;
int i = indexOf(obj);
if (i >= 0) {
removeElementAt(i);
return true;
}
return false;
}
//i=elementCount=0 elementCount=0 -> i=0
//將所有元素置空，但并未修改容量大小
public synchronized void removeAllElements() {
final Object[] es = elementData;
for (int to = elementCount, i = elementCount = 0; i < to; i++)
es[i] = null;
modCount++;
}
//手把手教你寫深拷貝
public synchronized Object clone() {
try {
@SuppressWarnings("unchecked")
Vector<E> v = (Vector<E>) super.clone();
v.elementData = https://www.cnblogs.com/angelMask/p/Arrays.copyOf(elementData, elementCount);
v.modCount = 0;
return v;
} catch (CloneNotSupportedException e) {
// this shouldn't happen, since we are Cloneable
throw new InternalError(e);
}
}
//也算是深拷貝吧?
public synchronized Object[] toArray() {
return Arrays.copyOf(elementData, elementCount);
}
//轉換成T[]實際上也是
@SuppressWarnings("unchecked")
public synchronized <T> T[] toArray(T[] a) {
//這里會出問題，因為傳入的陣列太小而無法接收，因此JDK被迫回傳了一個新的陣列
//那么傳進來的a的所有資料就會為空！
if (a.length < elementCount)
return (T[]) Arrays.copyOf(elementData, elementCount, a.getClass());
System.arraycopy(elementData, 0, a, 0, elementCount);
//意義是什么？應該和JVM的GC回收有關系，
if (a.length > elementCount)
a[elementCount] = null;
return a;
}
@SuppressWarnings("unchecked")
E elementData(int index) {
return (E) elementData[index];
}
@SuppressWarnings("unchecked")
static <E> E elementAt(Object[] es, int index) {
return (E) es[index];
}
public synchronized E get(int index) {
if (index >= elementCount)
throw new ArrayIndexOutOfBoundsException(index);
return elementData(index);
}
//回傳值是原來的資料
public synchronized E set(int index, E element) {
if (index >= elementCount)
throw new ArrayIndexOutOfBoundsException(index);
E oldValue = https://www.cnblogs.com/angelMask/p/elementData(index);
elementData[index] = element;
return oldValue;
}
//最尾增加元素，容量不夠就擴1
private void add(E e, Object[] elementData, int s) {
if (s == elementData.length)
elementData = grow();
elementData[s] = e;
elementCount = s + 1;
}
//丟，你沒有回傳false的情況設個boolean？難蚌
public synchronized boolean add(E e) {
modCount++;
add(e, elementData, elementCount);
return true;
}
//就換個名字?
public boolean remove(Object o) {
return removeElement(o);
}
//就引數調轉一下...
public void add(int index, E element) {
insertElementAt(element, index);
}
//換了名字又重寫了一遍...和removeElementAt相比加了個回傳值，回傳值是原來的元素
public synchronized E remove(int index) {
modCount++;
if (index >= elementCount)
throw new ArrayIndexOutOfBoundsException(index);
E oldValue = elementData(index);
int numMoved = elementCount - index - 1;
if (numMoved > 0)
System.arraycopy(elementData, index+1, elementData, index,
numMoved);
elementData[--elementCount] = null; // Let gc do its work
return oldValue;
}
//換了個名字
public void clear() {
removeAllElements();
}
//是否包含集合c的所有元素
public synchronized boolean containsAll(Collection<?> c) {
return super.containsAll(c);
}
//在vector最后增加c的所有元素
public boolean addAll(Collection<? extends E> c) {
Object[] a = c.toArray();
modCount++;
int numNew = a.length;
if (numNew == 0)
return false;
synchronized (this) {
Object[] elementData = this.elementData;
final int s = elementCount;
//確保又足夠的容量
if (numNew > elementData.length - s)
elementData = grow(s + numNew);
//將a從0開始的所有元素拷貝到..., 長度是numNew
System.arraycopy(a, 0, elementData, s, numNew);
elementCount = s + numNew;
return true;
}
}
//先看下面的bulkRemove()
public boolean removeAll(Collection<?> c) {
Objects.requireNonNull(c);
return bulkRemove(e -> c.contains(e));
}
//下面
public boolean retainAll(Collection<?> c) {
Objects.requireNonNull(c);
return bulkRemove(e -> !c.contains(e));
}
//下面
@Override
public boolean removeIf(Predicate<? super E> filter) {
Objects.requireNonNull(filter);
return bulkRemove(filter);
}
// A tiny bit set implementation
private static long[] nBits(int n) {
return new long[((n - 1) >> 6) + 1];
}
private static void setBit(long[] bits, int i) {
bits[i >> 6] |= 1L << i;
}
private static boolean isClear(long[] bits, int i) {
return (bits[i >> 6] & (1L << i)) == 0;
}
//不會
private synchronized boolean bulkRemove(Predicate<? super E> filter) {
int expectedModCount = modCount;
final Object[] es = elementData;
final int end = elementCount;
int i;
// Optimize for initial run of survivors
for (i = 0; i < end && !filter.test(elementAt(es, i)); i++)
;
// Tolerate predicates that reentrantly access the collection for
// read (but writers still get CME), so traverse once to find
// elements to delete, a second pass to physically expunge.
if (i < end) {
final int beg = i;
final long[] deathRow = nBits(end - beg);
deathRow[0] = 1L; // set bit 0
for (i = beg + 1; i < end; i++)
if (filter.test(elementAt(es, i)))
setBit(deathRow, i - beg);
if (modCount != expectedModCount)
throw new ConcurrentModificationException();
modCount++;
int w = beg;
for (i = beg; i < end; i++)
if (isClear(deathRow, i - beg))
es[w++] = es[i];
for (i = elementCount = w; i < end; i++)
es[i] = null;
return true;
} else {
if (modCount != expectedModCount)
throw new ConcurrentModificationException();
return false;
}
}
//在特定下標處插入所有集合中的元素
public synchronized boolean addAll(int index, Collection<? extends E> c) {
if (index < 0 || index > elementCount)
throw new ArrayIndexOutOfBoundsException(index);
Object[] a = c.toArray();
modCount++;
int numNew = a.length;
if (numNew == 0)
return false;
Object[] elementData = this.elementData;
final int s = elementCount;
if (numNew > elementData.length - s)
elementData = grow(s + numNew);
int numMoved = s - index;//計算原陣列中index后剩余元素的數量
if (numMoved > 0)
System.arraycopy(elementData, index,
elementData, index + numNew,
numMoved);//轉移index后的元素
System.arraycopy(a, 0, elementData, index, numNew);//將c賦入elementData
elementCount = s + numNew;
return true;
}
public synchronized boolean equals(Object o) {
return super.equals(o);
}
public synchronized int hashCode() {
return super.hashCode();
}
public synchronized String toString() {
return super.toString();
}
//切割陣列，其中原始碼中List分為是否實作了RandomAccess(隨機讀取)介面兩種
//vector是實作了隨機讀取介面的容器，擁有更高的讀寫效率
//JDK建議實作了隨機讀取的類使用fori遍歷而非iterator
public synchronized List subList(int fromIndex, int toIndex) {
return Collections.synchronizedList(super.subList(fromIndex, toIndex),
this);
}
//移除范圍中的元素,fromIndex是起始下標，toIndex末尾下標
protected synchronized void removeRange(int fromIndex, int toIndex) {
modCount++;
shiftTailOverGap(elementData, fromIndex, toIndex);
}
//lo是fromIndex, hi是toIndex
private void shiftTailOverGap(Object[] es, int lo, int hi) {
//將es toIndex后所有的元素拷貝到fromIndex后所有的元素的位置上
System.arraycopy(es, hi, es, lo, elementCount - hi);
//將elementCount-(toIndex-fromIndex)后的所有元素置空
for (int to = elementCount, i = (elementCount -= hi - lo); i < to; i++)
es[i] = null;
}
//序列化介面
@java.io.Serial
private void readObject(ObjectInputStream in)
throws IOException, ClassNotFoundException {
ObjectInputStream.GetField gfields = in.readFields();
int count = gfields.get("elementCount", 0);
Object[] data = https://www.cnblogs.com/angelMask/p/(Object[])gfields.get("elementData", null);
if (data =https://www.cnblogs.com/angelMask/p/= null && !gfields.defaulted("elementData") && count > 0) {
// If elementData is null due to 8276665 throwing this exception will not
// overwrite the original ClassNotFoundException exception.
// That exception has been recorded and will be thrown from OIS.readObject.
throw new ClassNotFoundException("elementData is null");
}
if (count < 0 || data =https://www.cnblogs.com/angelMask/p/= null || count > data.length) {
throw new StreamCorruptedException("Inconsistent vector internals");
}
elementCount = count;
elementData = https://www.cnblogs.com/angelMask/p/data.clone();
}
//序列化介面
@java.io.Serial
private void writeObject(java.io.ObjectOutputStream s)
throws java.io.IOException {
final java.io.ObjectOutputStream.PutField fields = s.putFields();
final Object[] data;
synchronized (this) {
fields.put("capacityIncrement", capacityIncrement);
fields.put("elementCount", elementCount);
data = https://www.cnblogs.com/angelMask/p/elementData.clone();
}
fields.put("elementData", data);
s.writeFields();
}
public synchronized ListIterator<E> listIterator(int index) {
if (index < 0 || index > elementCount)
throw new IndexOutOfBoundsException("Index: "+index);
return new ListItr(index);
}
public synchronized ListIterator<E> listIterator() {
return new ListItr(0);//一個繼承Itr并實作了ListIterator的內部類
}
public synchronized Iterator<E> iterator() {
return new Itr();//一個實作了iterator介面的內部類
}
private class Itr implements Iterator<E> {
int cursor; // 記錄著下一個元素的索引，起點是0，終點是elementCount
int lastRet = -1; // 記錄著當前元素的索引，lastRet=cursor-1
int expectedModCount = modCount;//快速失敗機制
public boolean hasNext() {
return cursor != elementCount;
}
//沒啥好看的
public E next() {
synchronized (Vector.this) {
checkForComodification();
int i = cursor;
if (i >= elementCount)
throw new NoSuchElementException();
cursor = i + 1;
return elementData(lastRet = i);
}
}
//當前的元素被移除，那么lastRet就要指向-1，而cursor就要指向當前元素（因為 remove()函式是使用arraycopy()實作的）
public void remove() {
if (lastRet == -1)
throw new IllegalStateException();
synchronized (Vector.this) {
checkForComodification();
Vector.this.remove(lastRet);//這里增加了modCount
expectedModCount = modCount;
}
cursor = lastRet;
lastRet = -1;
}
//函式式編程介面Consumer(lambda運算式和方法參考等等)
@Override
public void forEachRemaining(Consumer<? super E> action) {
Objects.requireNonNull(action);
synchronized (Vector.this) {
final int size = elementCount;
int i = cursor;
if (i >= size) {
return;
}
final Object[] es = elementData;
if (i >= es.length)
throw new ConcurrentModificationException();
while (i < size && modCount == expectedModCount)
action.accept(elementAt(es, i++));//這個將引數傳入你寫的lambda 運算式或者方法參考
// modCount==expectedModCount實作了快速失敗
cursor = i;
lastRet = i - 1;
checkForComodification();
}
}
final void checkForComodification() {
if (modCount != expectedModCount)
throw new ConcurrentModificationException();
}
}
//和上一個區別不大，也就調了些函式
final class ListItr extends Itr implements ListIterator<E> {
ListItr(int index) {
super();
cursor = index;
}
public boolean hasPrevious() {
return cursor != 0;
}
public int nextIndex() {
return cursor;
}
public int previousIndex() {
return cursor - 1;
}
public E previous() {
synchronized (Vector.this) {
checkForComodification();
int i = cursor - 1;
if (i < 0)
throw new NoSuchElementException();
cursor = i;
return elementData(lastRet = i);
}
}
public void set(E e) {
if (lastRet == -1)
throw new IllegalStateException();
synchronized (Vector.this) {
checkForComodification();
Vector.this.set(lastRet, e);
}
}
public void add(E e) {
int i = cursor;
synchronized (Vector.this) {
checkForComodification();
Vector.this.add(i, e);
expectedModCount = modCount;
}
cursor = i + 1;
lastRet = -1;
}
}
/**
* @throws NullPointerException {@inheritDoc}
*/
@Override
public synchronized void forEach(Consumer<? super E> action) {
Objects.requireNonNull(action);
final int expectedModCount = modCount;
final Object[] es = elementData;
final int size = elementCount;
for (int i = 0; modCount == expectedModCount && i < size; i++)
action.accept(elementAt(es, i));
if (modCount != expectedModCount)
throw new ConcurrentModificationException();
}
/**
* @throws NullPointerException {@inheritDoc}
*/
@Override
public synchronized void replaceAll(UnaryOperator<E> operator) {
Objects.requireNonNull(operator);
final int expectedModCount = modCount;
final Object[] es = elementData;
final int size = elementCount;
for (int i = 0; modCount == expectedModCount && i < size; i++)
es[i] = operator.apply(elementAt(es, i));
if (modCount != expectedModCount)
throw new ConcurrentModificationException();
// TODO(8203662): remove increment of modCount from ...
modCount++;
}
@SuppressWarnings("unchecked")
@Override
public synchronized void sort(Comparator<? super E> c) {
final int expectedModCount = modCount;
Arrays.sort((E[]) elementData, 0, elementCount, c);
if (modCount != expectedModCount)
throw new ConcurrentModificationException();
modCount++;
}
/**
* Creates a <em><a href="https://www.cnblogs.com/angelMask/p/Spliterator.html#binding">late-binding</a></em>
* and <em>fail-fast</em> {@link Spliterator} over the elements in this
* list.
*
* <p>The {@code Spliterator} reports {@link Spliterator#SIZED},
* {@link Spliterator#SUBSIZED}, and {@link Spliterator#ORDERED}.
* Overriding implementations should document the reporting of additional
* characteristic values.
*
* @return a {@code Spliterator} over the elements in this list
* @since 1.8
*/
@Override
public Spliterator<E> spliterator() {
return new VectorSpliterator(null, 0, -1, 0);
}
//行百里者半九十，我已經開擺了，
/** Similar to ArrayList Spliterator */
final class VectorSpliterator implements Spliterator<E> {
private Object[] array;
private int index; // current index, modified on advance/split
private int fence; // -1 until used; then one past last index
private int expectedModCount; // initialized when fence set
/** Creates new spliterator covering the given range. */
VectorSpliterator(Object[] array, int origin, int fence,
int expectedModCount) {
this.array = array;
this.index = origin;
this.fence = fence;
this.expectedModCount = expectedModCount;
}
private int getFence() { // initialize on first use
int hi;
if ((hi = fence) < 0) {
synchronized (Vector.this) {
array = elementData;
expectedModCount = modCount;
hi = fence = elementCount;
}
}
return hi;
}
public Spliterator<E> trySplit() {
int hi = getFence(), lo = index, mid = (lo + hi) >>> 1;
return (lo >= mid) ? null :
new VectorSpliterator(array, lo, index = mid, expectedModCount);
}
@SuppressWarnings("unchecked")
public boolean tryAdvance(Consumer<? super E> action) {
Objects.requireNonNull(action);
int i;
if (getFence() > (i = index)) {
index = i + 1;
action.accept((E)array[i]);
if (modCount != expectedModCount)
throw new ConcurrentModificationException();
return true;
}
return false;
}
@SuppressWarnings("unchecked")
public void forEachRemaining(Consumer<? super E> action) {
Objects.requireNonNull(action);
final int hi = getFence();
final Object[] a = array;
int i;
for (i = index, index = hi; i < hi; i++)
action.accept((E) a[i]);
if (modCount != expectedModCount)
throw new ConcurrentModificationException();
}
public long estimateSize() {
return getFence() - index;
}
public int characteristics() {
return Spliterator.ORDERED | Spliterator.SIZED | Spliterator.SUBSIZED;
}
}
void checkInvariants() {
// assert elementCount >= 0;
// assert elementCount == elementData.length || elementData[elementCount] == null;
}
}
ArrayList刨析
因為和Vector一樣都是實作了抽象類AbstractList
所以本質上是一樣的，不同的是，Vector的實作因為考慮了多執行緒的因素，原始碼應該會比ArrayList更高級，相應的，因為Vector考慮了多執行緒所以也會降低方法執行的速度和效率，
Stack刨析
public class Stack<E> extends Vector<E> {
public Stack() {
}
//在Vector陣列尾部壓入資料
public E push(E item) {
addElement(item);
return item;
}
//回傳并移除資料尾部元素
public synchronized E pop() {
E obj;
int len = size();
obj = peek();
removeElementAt(len - 1);
return obj;
}
//回傳陣列尾部元素
public synchronized E peek() {
int len = size();
if (len == 0)
throw new EmptyStackException();
return elementAt(len - 1);
}
//判空
public boolean empty() {
return size() == 0;
}
//從尾部開始找到最找出現o的下標
public synchronized int search(Object o) {
int i = lastIndexOf(o);
if (i >= 0) {
return size() - i;
}
return -1;
}
//序列化
@java.io.Serial
private static final long serialVersionUID = 1224463164541339165L;
}
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標籤：Java