Java ArrayList源代码学习笔记
来源：互联网 发布：南京行知基地住宿条件 编辑：程序博客网 时间：2024/06/08 09:49
<span style="font-size:18px;"> private static final int MIN_CAPACITY_INCREMENT = 12;</span>
Object[] newArray = new Object[s + (s < (MIN_CAPACITY_INCREMENT / 2) ? MIN_CAPACITY_INCREMENT : s >> 1)];
如上，是增量的计算方法。
构造方法：
<span style="font-size:18px;">public ArrayList(int capacity) { if (capacity < 0) { throw new IllegalArgumentException("capacity < 0: " + capacity); } array = (capacity == 0 ? EmptyArray.OBJECT : new Object[capacity]); }</span>根据capacity确定大小，若小于0则抛出异常。否则，如果为0，则初始化空数据；大于0，则根据capacity的大小初始化数组。
注意：如果只有两种情况，就不要用if ,else,可以用（..? ..：...）
public ArrayList(Collection<? extends E> collection) { if (collection == null) { throw new NullPointerException("collection == null"); } Object[] a = collection.toArray(); if (a.getClass() != Object[].class) { Object[] newArray = new Object[a.length]; System.arraycopy(a, 0, newArray, 0, a.length); a = newArray; } array = a; size = a.length; } 数组的快速复制，可以使用：System.arraycopy(a, 0, newArray, 0, a.length);贴下ArrayList的源码：
@Override public boolean add(E object) { Object[] a = array; int s = size; if (s == a.length) { Object[] newArray = new Object[s + (s < (MIN_CAPACITY_INCREMENT / 2) ? MIN_CAPACITY_INCREMENT : s >> 1)]; System.arraycopy(a, 0, newArray, 0, s); array = a = newArray; } a[s] = object; size = s + 1; modCount++; return true; } /** * Inserts the specified object into this {@code ArrayList} at the specified * location. The object is inserted before any previous element at the * specified location. If the location is equal to the size of this * {@code ArrayList}, the object is added at the end. * * @param index * the index at which to insert the object. * @param object * the object to add. * @throws IndexOutOfBoundsException * when {@code location < 0 || location > size()} */ @Override public void add(int index, E object) { Object[] a = array; int s = size; if (index > s || index < 0) { throwIndexOutOfBoundsException(index, s); } if (s < a.length) { System.arraycopy(a, index, a, index + 1, s - index); } else { // assert s == a.length; Object[] newArray = new Object[newCapacity(s)]; System.arraycopy(a, 0, newArray, 0, index); System.arraycopy(a, index, newArray, index + 1, s - index); array = a = newArray; } a[index] = object; size = s + 1; modCount++; } /** * This method controls the growth of ArrayList capacities. It represents * a time-space tradeoff: we don't want to grow lists too frequently * (which wastes time and fragments storage), but we don't want to waste * too much space in unused excess capacity. * * NOTE: This method is inlined into {@link #add(Object)} for performance. * If you change the method, change it there too! */ private static int newCapacity(int currentCapacity) { int increment = (currentCapacity < (MIN_CAPACITY_INCREMENT / 2) ? MIN_CAPACITY_INCREMENT : currentCapacity >> 1); return currentCapacity + increment; } /** * Adds the objects in the specified collection to this {@code ArrayList}. * * @param collection * the collection of objects. * @return {@code true} if this {@code ArrayList} is modified, {@code false} * otherwise. */ @Override public boolean addAll(Collection<? extends E> collection) { Object[] newPart = collection.toArray(); int newPartSize = newPart.length; if (newPartSize == 0) { return false; } Object[] a = array; int s = size; int newSize = s + newPartSize; // If add overflows, arraycopy will fail if (newSize > a.length) { int newCapacity = newCapacity(newSize - 1); // ~33% growth room Object[] newArray = new Object[newCapacity]; System.arraycopy(a, 0, newArray, 0, s); array = a = newArray; } System.arraycopy(newPart, 0, a, s, newPartSize); size = newSize; modCount++; return true; } /** * Inserts the objects in the specified collection at the specified location * in this List. The objects are added in the order they are returned from * the collection's iterator. * * @param index * the index at which to insert. * @param collection * the collection of objects. * @return {@code true} if this {@code ArrayList} is modified, {@code false} * otherwise. * @throws IndexOutOfBoundsException * when {@code location < 0 || location > size()} */ @Override public boolean addAll(int index, Collection<? extends E> collection) { int s = size; if (index > s || index < 0) { throwIndexOutOfBoundsException(index, s); } Object[] newPart = collection.toArray(); int newPartSize = newPart.length; if (newPartSize == 0) { return false; } Object[] a = array; int newSize = s + newPartSize; // If add overflows, arraycopy will fail if (newSize <= a.length) { System.arraycopy(a, index, a, index + newPartSize, s - index); } else { int newCapacity = newCapacity(newSize - 1); // ~33% growth room Object[] newArray = new Object[newCapacity]; System.arraycopy(a, 0, newArray, 0, index); System.arraycopy(a, index, newArray, index + newPartSize, s-index); array = a = newArray; } System.arraycopy(newPart, 0, a, index, newPartSize); size = newSize; modCount++; return true; } /** * This method was extracted to encourage VM to inline callers. * TODO: when we have a VM that can actually inline, move the test in here too! */ static IndexOutOfBoundsException throwIndexOutOfBoundsException(int index, int size) { throw new IndexOutOfBoundsException("Invalid index " + index + ", size is " + size); } /** * Removes all elements from this {@code ArrayList}, leaving it empty. * * @see #isEmpty * @see #size */ @Override public void clear() { if (size != 0) { Arrays.fill(array, 0, size, null); size = 0; modCount++; } } /** * Returns a new {@code ArrayList} with the same elements, the same size and * the same capacity as this {@code ArrayList}. * * @return a shallow copy of this {@code ArrayList} * @see java.lang.Cloneable */ @Override public Object clone() { try { ArrayList<?> result = (ArrayList<?>) super.clone(); result.array = array.clone(); return result; } catch (CloneNotSupportedException e) { throw new AssertionError(); } } /** * Ensures that after this operation the {@code ArrayList} can hold the * specified number of elements without further growing. * * @param minimumCapacity * the minimum capacity asked for. */ public void ensureCapacity(int minimumCapacity) { Object[] a = array; if (a.length < minimumCapacity) { Object[] newArray = new Object[minimumCapacity]; System.arraycopy(a, 0, newArray, 0, size); array = newArray; modCount++; } } @SuppressWarnings("unchecked") @Override public E get(int index) { if (index >= size) { throwIndexOutOfBoundsException(index, size); } return (E) array[index]; } /** * Returns the number of elements in this {@code ArrayList}. * * @return the number of elements in this {@code ArrayList}. */ @Override public int size() { return size; } @Override public boolean isEmpty() { return size == 0; } /** * Searches this {@code ArrayList} for the specified object. * * @param object * the object to search for. * @return {@code true} if {@code object} is an element of this * {@code ArrayList}, {@code false} otherwise */ @Override public boolean contains(Object object) { Object[] a = array; int s = size; if (object != null) { for (int i = 0; i < s; i++) { if (object.equals(a[i])) { return true; } } } else { for (int i = 0; i < s; i++) { if (a[i] == null) { return true; } } } return false; } @Override public int indexOf(Object object) { Object[] a = array; int s = size; if (object != null) { for (int i = 0; i < s; i++) { if (object.equals(a[i])) { return i; } } } else { for (int i = 0; i < s; i++) { if (a[i] == null) { return i; } } } return -1; } @Override public int lastIndexOf(Object object) { Object[] a = array; if (object != null) { for (int i = size - 1; i >= 0; i--) { if (object.equals(a[i])) { return i; } } } else { for (int i = size - 1; i >= 0; i--) { if (a[i] == null) { return i; } } } return -1; } /** * Removes the object at the specified location from this list. * * @param index * the index of the object to remove. * @return the removed object. * @throws IndexOutOfBoundsException * when {@code location < 0 || location >= size()} */ @Override public E remove(int index) { Object[] a = array; int s = size; if (index >= s) { throwIndexOutOfBoundsException(index, s); } @SuppressWarnings("unchecked") E result = (E) a[index]; System.arraycopy(a, index + 1, a, index, --s - index); a[s] = null; // Prevent memory leak size = s; modCount++; return result; } @Override public boolean remove(Object object) { Object[] a = array; int s = size; if (object != null) { for (int i = 0; i < s; i++) { if (object.equals(a[i])) { System.arraycopy(a, i + 1, a, i, --s - i); a[s] = null; // Prevent memory leak size = s; modCount++; return true; } } } else { for (int i = 0; i < s; i++) { if (a[i] == null) { System.arraycopy(a, i + 1, a, i, --s - i); a[s] = null; // Prevent memory leak size = s; modCount++; return true; } } } return false; } @Override protected void removeRange(int fromIndex, int toIndex) { if (fromIndex == toIndex) { return; } Object[] a = array; int s = size; if (fromIndex >= s) { throw new IndexOutOfBoundsException("fromIndex " + fromIndex + " >= size " + size); } if (toIndex > s) { throw new IndexOutOfBoundsException("toIndex " + toIndex + " > size " + size); } if (fromIndex > toIndex) { throw new IndexOutOfBoundsException("fromIndex " + fromIndex + " > toIndex " + toIndex); } System.arraycopy(a, toIndex, a, fromIndex, s - toIndex); int rangeSize = toIndex - fromIndex; Arrays.fill(a, s - rangeSize, s, null); size = s - rangeSize; modCount++; } /** * Replaces the element at the specified location in this {@code ArrayList} * with the specified object. * * @param index * the index at which to put the specified object. * @param object * the object to add. * @return the previous element at the index. * @throws IndexOutOfBoundsException * when {@code location < 0 || location >= size()} */ @Override public E set(int index, E object) { Object[] a = array; if (index >= size) { throwIndexOutOfBoundsException(index, size); } @SuppressWarnings("unchecked") E result = (E) a[index]; a[index] = object; return result; } /** * Returns a new array containing all elements contained in this * {@code ArrayList}. * * @return an array of the elements from this {@code ArrayList} */ @Override public Object[] toArray() { int s = size; Object[] result = new Object[s]; System.arraycopy(array, 0, result, 0, s); return result; } /** * Returns an array containing all elements contained in this * {@code ArrayList}. If the specified array is large enough to hold the * elements, the specified array is used, otherwise an array of the same * type is created. If the specified array is used and is larger than this * {@code ArrayList}, the array element following the collection elements * is set to null. * * @param contents * the array. * @return an array of the elements from this {@code ArrayList}. * @throws ArrayStoreException * when the type of an element in this {@code ArrayList} cannot * be stored in the type of the specified array. */ @Override public <T> T[] toArray(T[] contents) { int s = size; if (contents.length < s) { @SuppressWarnings("unchecked") T[] newArray = (T[]) Array.newInstance(contents.getClass().getComponentType(), s); contents = newArray; } System.arraycopy(this.array, 0, contents, 0, s); if (contents.length > s) { contents[s] = null; } return contents; } /** * Sets the capacity of this {@code ArrayList} to be the same as the current * size. * * @see #size */ public void trimToSize() { int s = size; if (s == array.length) { return; } if (s == 0) { array = EmptyArray.OBJECT; } else { Object[] newArray = new Object[s]; System.arraycopy(array, 0, newArray, 0, s); array = newArray; } modCount++; } @Override public Iterator<E> iterator() { return new ArrayListIterator(); } private class ArrayListIterator implements Iterator<E> { /** Number of elements remaining in this iteration */ private int remaining = size; /** Index of element that remove() would remove, or -1 if no such elt */ private int removalIndex = -1; /** The expected modCount value */ private int expectedModCount = modCount; public boolean hasNext() { return remaining != 0; } @SuppressWarnings("unchecked") public E next() { ArrayList<E> ourList = ArrayList.this; int rem = remaining; if (ourList.modCount != expectedModCount) { throw new ConcurrentModificationException(); } if (rem == 0) { throw new NoSuchElementException(); } remaining = rem - 1; return (E) ourList.array[removalIndex = ourList.size - rem]; } public void remove() { Object[] a = array; int removalIdx = removalIndex; if (modCount != expectedModCount) { throw new ConcurrentModificationException(); } if (removalIdx < 0) { throw new IllegalStateException(); } System.arraycopy(a, removalIdx + 1, a, removalIdx, remaining); a[--size] = null; // Prevent memory leak removalIndex = -1; expectedModCount = ++modCount; } } @Override public int hashCode() { Object[] a = array; int hashCode = 1; for (int i = 0, s = size; i < s; i++) { Object e = a[i]; hashCode = 31 * hashCode + (e == null ? 0 : e.hashCode()); } return hashCode; } @Override public boolean equals(Object o) { if (o == this) { return true; } if (!(o instanceof List)) { return false; } List<?> that = (List<?>) o; int s = size; if (that.size() != s) { return false; } Object[] a = array; if (that instanceof RandomAccess) { for (int i = 0; i < s; i++) { Object eThis = a[i]; Object ethat = that.get(i); if (eThis == null ? ethat != null : !eThis.equals(ethat)) { return false; } } } else { // Argument list is not random access; use its iterator Iterator<?> it = that.iterator(); for (int i = 0; i < s; i++) { Object eThis = a[i]; Object eThat = it.next(); if (eThis == null ? eThat != null : !eThis.equals(eThat)) { return false; } } } return true; } private static final long serialVersionUID = 8683452581122892189L; private void writeObject(ObjectOutputStream stream) throws IOException { stream.defaultWriteObject(); stream.writeInt(array.length); for (int i = 0; i < size; i++) { stream.writeObject(array[i]); } } private void readObject(ObjectInputStream stream) throws IOException, ClassNotFoundException { stream.defaultReadObject(); int cap = stream.readInt(); if (cap < size) { throw new InvalidObjectException( "Capacity: " + cap + " < size: " + size); } array = (cap == 0 ? EmptyArray.OBJECT : new Object[cap]); for (int i = 0; i < size; i++) { array[i] = stream.readObject(); } } } 0 0
- Java ArrayList源代码学习笔记
- Java ArrayList学习笔记
- 【Java学习笔记】ArrayList泛型
- java集合-ArrayList学习笔记
- ArrayList 源代码笔记
- Java源代码走读--ArrayList
- 【源代码】java.util.ArrayList
- java ArrayList源代码实现
- java ArrayList 源代码分析
- 【预习笔记】读几个Java集合类源代码—ArrayList
- 共同学习Java源代码--数据结构--ArrayList类(一)
- 共同学习Java源代码--数据结构--ArrayList类(二)
- 共同学习Java源代码--数据结构--ArrayList类(三)
- 共同学习Java源代码--数据结构--ArrayList类(四)
- 共同学习Java源代码--数据结构--ArrayList类(五)
- 共同学习Java源代码--数据结构--ArrayList类(六)
- 共同学习Java源代码--数据结构--ArrayList类(七)
- 共同学习Java源代码--数据结构--ArrayList类(八)
- 字典使用
- linux内核启动时，第一次创建页表
- jQuery炫酷3D旋转幻灯片特效插件
- 1.3 C++中的并行和多线程
- Redis 集群方案
- Java ArrayList源代码学习笔记
- C++小知识（不断更新）
- 不水好好学——Kali Linux初识
- eclipse link方式安装插件安装不上
- 权威披露2014微信十大最火谣言 | 调查称女性最爱传谣，你服不服？
- JSp文件修改不生效的解决办法
- Spring事务配置的五种方式
- 女人眼里，啥样男人最强悍?
- 很舒服的几句话，心静，人就不会累了
