知识大全 使用Lists
Posted 元素
篇首语:愿君学长松,慎勿作桃李。本文由小常识网(cha138.com)小编为大家整理,主要介绍了知识大全 使用Lists相关的知识,希望对你有一定的参考价值。
使用Lists 以下文字资料是由(全榜网网www.cha138.com)小编为大家搜集整理后发布的内容,让我们赶快一起来看一下吧!
> 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 允许我们快速访问元素 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蓋了一组不同的行为 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 //: List java // Things you can do with Lists package c newcollections; import java util *; public class List // Wrap Collection fill() for convenience: public static List fill(List a) return (List)Collection 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 = ; i < a.size(); 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 1 a.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 = ntains("1"); // Is it in there? // Is the entire collection in there? b = ntainsAll(fill(new ArrayList())); // Lists allow random access, which is cheap // for ArrayList, expensive for LinkedList: o = a.get(1); // Get object at location 1 i = 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 = erator(); // Ordinary Iterator lit = a.listIterator(); // ListIterator lit = a.listIterator(3); // Start at loc 3 i = a.lastIndexOf("1"); // Last match i = a.lastIndexOf("1", 2); // ...after loc 2 a.remove(1); // Remove location 1 a.remove("3"); // Remove this object a.set(1, "y"); // Set location 1 to "y" // Keep everything that\'s in the argument // (the intersection of the o 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("o"); 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。Tw.wiNGwit而且尽管捕获了返回值,但是并未使用它。在某些情况下,之所以不捕获返回值,是由于它们没有什么特别的用处。在正式使用它们前,应仔细研究一下自己的联机文档,掌握这些方法完整、正确的用法。 cha138/Article/program/Java/JSP/201311/19717相关参考