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1，继承结构图：/*** The root interface in the <i>collection hierarchy</i>. A collection* represents a group of objects, known as its <i>elements</i>. Some* collections allow duplicate elements and others do not. Some are ordered* and others unordered.
package java.lang;import java.util.Iterator;/** Implementing this interface allows an object to be the target of* the "foreach" statement.* @since 1.5*/public interface Iterable<T> {/*** Returns an iterator over a set of elements of type T.** @return an Iterator.*/Iterator<T> iterator();}
public interface Iterator<E> {boolean hasNext();E next();void remove();}
* <p>This interface is a member of the* <a href="{@docRoot}/../technotes/guides/collections/index.html">* Java Collections Framework</a>.** @author Josh Bloch* @author Neal Gafter* @version 1.55, 04/21/06* @see Set* @see List* @see Map* @see SortedSet* @see SortedMap* @see HashSet* @see TreeSet* @see ArrayList* @see LinkedList* @see Vector* @see Collections* @see Arrays* @see AbstractCollection* @since 1.2*/
public abstract class AbstractCollection<E> implements Collection<E>
/*** {@inheritDoc}** <p>This implementation returns <tt>size() == 0</tt>.*/public boolean isEmpty() {return size() == 0;}
public boolean contains(Object o) {Iterator<E> e = iterator();if (o==null) {while (e.hasNext())if (e.next()==null)return true;} else {while (e.hasNext())if (o.equals(e.next()))return true;}return false;}
public boolean remove(Object o) {Iterator<E> e = iterator();if (o==null) {while (e.hasNext()) {if (e.next()==null) {e.remove();return true;}}} else {while (e.hasNext()) {if (o.equals(e.next())) {e.remove();return true;}}}return false;}
public boolean addAll(Collection<? extends E> c) {boolean modified = false;Iterator<? extends E> e = c.iterator();while (e.hasNext()) {if (add(e.next()))modified = true;}return modified;}
An ordered collection (also known as a <i>sequence</i>).
Unlike sets, lists typically allow duplicate elements.
The <tt>List</tt> interface provides a special iterator, called a* <tt>ListIterator</tt>, that allows element insertion and replacement, and* bidirectional access in addition to the normal operations that the* <tt>Iterator</tt> interface provides.
List list = Collections.synchronizedList(new ArrayList(...));
public class TestAdd {public static void main(String[] args) {long startTime = System.currentTimeMillis();List<Integer> lists = new ArrayList<Integer>();//测试add方法for(int i = 0 ; i < 1000000; i++){lists.add(1);}long endTime = System.currentTimeMillis();System.out.println("add添加1000000元素，用时： " + (endTime - startTime));//输出32//add 一个元素的时间startTime = System.currentTimeMillis();lists.add(2);endTime = System.currentTimeMillis();System.out.println("add添加1元素，用时： " + (endTime - startTime));//输出0//get 一个元素startTime = System.currentTimeMillis();lists.get(2);endTime = System.currentTimeMillis();System.out.println("get元素，用时： " + (endTime - startTime));//输出0}}
long startTime = System.currentTimeMillis();List<Integer> lists = new ArrayList<Integer>(1000000);//测试add方法for(int i = 0 ; i < 1000000; i++){lists.add(1);}long endTime = System.currentTimeMillis();System.out.println("add添加1000000元素，用时： " + (endTime - startTime));//输出12
startTime = System.currentTimeMillis();Iterator<Integer> iter = lists.iterator();int a ;while(iter.hasNext()){a = iter.next();}endTime = System.currentTimeMillis();System.out.println("迭代器元素，用时： " + (endTime - startTime));//输出33
private transient Object[] elementData;
public ArrayList(int initialCapacity) {super();if (initialCapacity < 0)throw new IllegalArgumentException("Illegal Capacity: "+initialCapacity);this.elementData = new Object[initialCapacity];}
public ArrayList() {this(10);}
public ArrayList(Collection<? extends E> c) {elementData = c.toArray();size = elementData.length;// c.toArray might (incorrectly) not return Object[] (see 6260652)if (elementData.getClass() != Object[].class)elementData = Arrays.copyOf(elementData, size, Object[].class);}
public static <T,U> T[] copyOf(U[] original, int newLength, Class<? extends T[]> newType) {T[] copy = ((Object)newType == (Object)Object[].class)? (T[]) new Object[newLength]: (T[]) Array.newInstance(newType.getComponentType(), newLength);System.arraycopy(original, 0, copy, 0,Math.min(original.length, newLength));return copy;}
public static native void arraycopy(Object src, int srcPos,Object dest, int destPos,int length);
public boolean add(E e) {ensureCapacity(size + 1); // Increments modCount!!elementData[size++] = e;return true;}
public void ensureCapacity(int minCapacity) {modCount++;int oldCapacity = elementData.length;if (minCapacity > oldCapacity) {Object oldData[] = elementData;int newCapacity = (oldCapacity * 3)/2 + 1;if (newCapacity < minCapacity)newCapacity = minCapacity;// minCapacity is usually close to size, so this is a win:elementData = Arrays.copyOf(elementData, newCapacity);}}
public E remove(int index) {RangeCheck(index);//确保索引位置未超出最大size，超出则抛出异常。modCount++;//记录表结构修改计数器E oldValue = (E) elementData[index];int numMoved = size - index - 1;if (numMoved > 0)System.arraycopy(elementData, index+1, elementData, index,numMoved);//将后续元素均向前移动一位elementData[--size] = null; // Let gc do its workreturn oldValue;}
public E get(int index) {RangeCheck(index);return (E) elementData[index];}
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原文地址：http://blog.csdn.net/mergades/article/details/42917301
