标签：com arraylist odi imp 迭代 ted ati efault 包含
ArrayList是一个容量可动态增长的“数组”。 有下面ArrayList实现的源码可以看到，它继承了AbstractList抽象类，实现了List、RandomAccess、Cloneable、java.io.Serializable四个接口
public class ArrayList<E> extends AbstractList<E>
implements List<E>, RandomAccess, Cloneable, java.io.Serializable{}
ArrayList()
// transient Object[] elementData;
// private static final Object[] DEFAULTCAPACITY_EMPTY_ELEMENTDATA = {}
public ArrayList() {
this.elementData = DEFAULTCAPACITY_EMPTY_ELEMENTDATA;
}
ArrayList(int initialCapacity)
看下面的源码，如果初始容量大于0，则正常传入一个数组；等于0，则空；小于0，则返回异常。
public ArrayList(int initialCapacity) {
if (initialCapacity > 0) {
this.elementData = new Object[initialCapacity];
} else if (initialCapacity == 0) {
this.elementData = EMPTY_ELEMENTDATA;
} else {
throw new IllegalArgumentException("Illegal Capacity: "+
initialCapacity);
}
}
ArrayList(Collection<? extends E> c)
传入一个列表作为初始化参数
public ArrayList(Collection<? extends E> c) {
elementData = c.toArray();
if ((size = elementData.length) != 0) {
// c.toArray might (incorrectly) not return Object[] (see 6260652)
if (elementData.getClass() != Object[].class)
elementData = Arrays.copyOf(elementData, size, Object[].class);
} else {
// replace with empty array.
this.elementData = EMPTY_ELEMENTDATA;
}
}
add(E e) 添加一个元素到列表的末尾， 先长度加1，然后元素加入末尾。返回值为boolean
public boolean add(E e) {
ensureCapacityInternal(size + 1); // Increments modCount!!
elementData[size++] = e;
return true;
}
add(int index, E element) 在指定的index位置加入元素，返回值为boolean
public void add(int index, E element) {
rangeCheckForAdd(index);
ensureCapacityInternal(size + 1); // Increments modCount!!
System.arraycopy(elementData, index, elementData, index + 1,
size - index);
elementData[index] = element;
size++;
}
addAll(Collection<? extends E> c) 添加一个指定的集合到元素的末尾，返回值为boolean
public boolean addAll(Collection<? extends E> c) {
Object[] a = c.toArray();
int numNew = a.length;
ensureCapacityInternal(size + numNew); // Increments modCount
System.arraycopy(a, 0, elementData, size, numNew);
size += numNew;
return numNew != 0;
}
remove(Object o) 删除列表中第一个出现的o元素。返回值boolean
public boolean remove(Object o) {
if (o == null) {
for (int index = 0; index < size; index++)
if (elementData[index] == null) {
fastRemove(index);
return true;
}
} else {
for (int index = 0; index < size; index++)
if (o.equals(elementData[index])) {
fastRemove(index);
return true;
}
}
return false;
}
remove(int index) 删除指定index索引位置处的元素,返回值为删除的元素
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; // clear to let GC do its work
return oldValue;
}
removeAll(Collection<?> c) 从arraylist中删除c中包含的所有元素，返回值为boolean
public boolean removeAll(Collection<?> c) {
Objects.requireNonNull(c);
return batchRemove(c, false);
}
removeRange(int fromIndex, int toIndex) 删除从fromIndex到toIndex位置出的所有元素
protected void removeRange(int fromIndex, int toIndex) {
modCount++;
int numMoved = size - toIndex;
System.arraycopy(elementData, toIndex, elementData, fromIndex,
numMoved);
// clear to let GC do its work
int newSize = size - (toIndex-fromIndex);
for (int i = newSize; i < size; i++) {
elementData[i] = null;
}
size = newSize;
}
clear() 删除所有元素
public void clear() {
modCount++;
// clear to let GC do its work
for (int i = 0; i < size; i++)
elementData[i] = null;
size = 0;
}
set(int index, E element) 用element替换index位置上的元素
public E set(int index, E element) {
rangeCheck(index);
E oldValue = elementData(index);
elementData[index] = element;
return oldValue;
}
sort(Comparator<? super E> c) 按照指定的规则进行排序 [排序再更新]
public void sort(Comparator<? super E> c) {
final int expectedModCount = modCount;
Arrays.sort((E[]) elementData, 0, size, c);
if (modCount != expectedModCount) {
throw new ConcurrentModificationException();
}
modCount++;
}
retainAll(Collection<?> c) 保留列表中出现过的元素，返回boolean
public boolean retainAll(Collection<?> c) {
Objects.requireNonNull(c);
return batchRemove(c, true);
}
isEmpty() 判断列表是否为空，如果为空返回true，否则false
public boolean isEmpty() {
return size == 0;
}
iterator() 返回列表迭代器
public Iterator<E> iterator() {
return new Itr();
}
size() 返回元素个数,int类型
public int size() {
return size;
}
contains(Object o) 如果队列中有o元素，则返回true，否则false
public boolean contains(Object o) {
return indexOf(o) >= 0;
}
get(int index) 返回index位置处的元素
public E get(int index) {
rangeCheck(index);
return elementData(index);
}
indexOf(Object o) 返回元素o第一次出现所在的索引位置信息，如果不存在，返回-1
public int indexOf(Object o) {
if (o == null) {
for (int i = 0; i < size; i++)
if (elementData[i]==null)
return i;
} else {
for (int i = 0; i < size; i++)
if (o.equals(elementData[i]))
return i;
}
return -1;
}
lastIndexOf(Object o) 返回元素o最后一次出现所在的索引位置信息，如果不存在，返回-1
public int lastIndexOf(Object o) {
if (o == null) {
for (int i = size-1; i >= 0; i--)
if (elementData[i]==null)
return i;
} else {
for (int i = size-1; i >= 0; i--)
if (o.equals(elementData[i]))
return i;
}
return -1;
}
subList(int fromIndex, int toIndex) 返回从fromIndex 到 toIndex的元素，返回值List
public List<E> subList(int fromIndex, int toIndex) {
subListRangeCheck(fromIndex, toIndex, size);
return new SubList(this, 0, fromIndex, toIndex);
}
toArray() 返回一个包含arrayList中所有元素的数组，返回值为Object[] 并不改变原先的arrayList
public Object[] toArray() {
return Arrays.copyOf(elementData, size);
}
标签：com arraylist odi imp 迭代 ted ati efault 包含
原文地址：https://www.cnblogs.com/Sinkinghost/p/12818447.html
