List（接口） 顺序是List最重要的特性；它可保证元素按照规定的顺序排列。List为Collection添加了大量方法，以便我们在List中部插入和删除元素（只推荐对LinkedList这样做）。List也会生成一个ListIterator（列表反复器），利用它可在一个列表里朝两个方向遍历，同时插入和删除位于列表中部的元素（同样地，只建议对LinkedList这样做）
ArrayList＊ 由一个数组后推得到的List。作为一个常规用途的对象容器使用，用于替换原先的Vector。答应我们快速访问元素，但在从列表中部插入和删除元素时，速度却嫌稍慢。一般只应该用ListIterator对一个ArrayList进行向前和向后遍历，不要用它删除和插入元素；与LinkedList相比，它的效率要低许多
LinkedList 提供优化的顺序访问性能，同时可以高效率地在列表中部进行插入和删除操作。但在进行随机访问时，速度却相当慢，此时应换用ArrayList。也提供了addFirst()，addLast()，getFirst()，getLast()，removeFirst()以及removeLast()（未在任何接口或基础类中定义），以便将其作为一个规格、队列以及一个双向队列使用
下面这个例子中的方法每个都覆盖了一组不同的行为：每个列表都能做的事情（basicTest()），通过一个反复器遍历（iterMotion()）、用一个反复器改变某些东西（iterManipulation()）、体验列表处理的效果（testVisual()）以及只有LinkedList才能做的事情等：
//: List1.java
// Things you can do with Lists
package c08.newcollections;
import java.util.*;
public class List1 {
// Wrap Collection1.fill() for convenience:
public static List fill(List a) {
return (List)Collection1.fill(a);
}
// You can use an Iterator, just as with a
// Collection, but you can also use random
// access with get():
public static void PRint(List a) {
for(int i = 0; i System.out.print(a.get(i) + " ");System.out.println();}static boolean b;static Object o;static int i;static Iterator it;static ListIterator lit;public static void basicTest(List a) {a.add(1, "x"); // Add at location 1a.add("x"); // Add at end// Add a collection:a.addAll(fill(new ArrayList()));// Add a collection starting at location 3:a.addAll(3, fill(new ArrayList()));b = a.contains("1"); // Is it in there?// Is the entire collection in there?b = a.containsAll(fill(new ArrayList()));// Lists allow random access, which is cheap// for ArrayList, eXPensive for LinkedList:o = a.get(1); // Get object at location 1i = a.indexOf("1"); // Tell index of object// indexOf, starting search at location 2:i = a.indexOf("1", 2);b = a.isEmpty(); // Any elements inside?it = a.iterator(); // Ordinary Iteratorlit = a.listIterator(); // ListIteratorlit = a.listIterator(3); // Start at loc 3i = a.lastIndexOf("1"); // Last matchi = a.lastIndexOf("1", 2); // ...after loc 2a.remove(1); // Remove location 1a.remove("3"); // Remove this objecta.set(1, "y"); // Set location 1 to "y"// Keep everything that's in the argument// (the intersection of the two sets):a.retainAll(fill(new ArrayList()));// Remove elements in this range:a.removeRange(0, 2);// Remove everything that's in the argument:a.removeAll(fill(new ArrayList()));i = a.size(); // How big is it?a.clear(); // Remove all elements}public static void iterMotion(List a) {ListIterator it = a.listIterator();b = it.hasNext();b = it.hasprevious();
o = it.next();
i = it.nextIndex();
o = it.previous();
i = it.previousIndex();
}
public static void iterManipulation(List a) {
ListIterator it = a.listIterator();
it.add("47");
// Must move to an element after add():
it.next();
// Remove the element that was just prodUCed:
it.remove();
// Must move to an element after remove():
it.next();
// Change the element that was just produced:
it.set("47");
}
public static void testVisual(List a) {
print(a);
List b = new ArrayList();
fill(b);
System.out.print("b = ");
print(b);
a.addAll(b);
a.addAll(fill(new ArrayList()));
print(a);
// Shrink the list by removing all the
// elements beyond the first 1/2 of the list
System.out.println(a.size());
System.out.println(a.size()/2);
a.removeRange(a.size()/2, a.size()/2 + 2);
print(a);
// Insert, remove, and replace elements
// using a ListIterator:
ListIterator x = a.listIterator(a.size()/2);
x.add("one");
print(a);
System.out.println(x.next());
x.remove();
System.out.println(x.next());
x.set("47");
print(a);
// Traverse the list backwards:
x = a.listIterator(a.size());
while(x.hasPrevious())
System.out.print(x.previous() + " ");
System.out.println();
System.out.println("testVisual finished");
}
// There are some things that only
// LinkedLists can do:
public static void testLinkedList() {
LinkedList ll = new LinkedList();
Collection1.fill(ll, 5);
print(ll);
// Treat it like a stack, pushing:
ll.addFirst("one");
ll.addFirst("two");
print(ll);
// Like "peeking" at the top of a stack:
System.out.println(ll.getFirst());
// Like popping a stack:
System.out.println(ll.removeFirst());
System.out.println(ll.removeFirst());
// Treat it like a queue, pulling elements
// off the tail end:
System.out.println(ll.removeLast());
// With the above Operations, it's a dequeue!
print(ll);
}
public static void main(String args[]) {
// Make and fill a new list each time:
basicTest(fill(new LinkedList()));
basicTest(fill(new ArrayList()));
iterMotion(fill(new LinkedList()));
iterMotion(fill(new ArrayList()));
iterManipulation(fill(new LinkedList()));
iterManipulation(fill(new ArrayList()));
testVisual(fill(new LinkedList()));
testLinkedList();
}
} ///:~
在basicTest()和iterMotiion()中，只是简单地发出调用，以便揭示出正确的语法。而且尽管捕捉了返回值，但是并未使用它。在某些情况下，之所以不捕捉返回值，是由于它们没有什么非凡的用处。在正式使用它们前，应仔细研究一下自己的联机文档，把握这些方法完整、正确的用法。
