Java集合框架-List(四)

Vector现在基本已经被ArrayList取代。但是vector中有一个elements()方法，返回的是枚举类型 Enumeration<E>。

package com.test.list;import java.util.Enumeration;import java.util.Vector;public class VectorDemo{public static void main(String[] args){Vector<String> list = new Vector<String>();list.add("Kevin");list.add("John");list.add("Clare");list.add("Gary");//使用elements()方法，返回的是枚举类型 Enumeration<E>//枚举是Vector特有的取出方式for(Enumeration<String> en = list.elements(); en.hasMoreElements();){System.out.println(en.nextElement());}}}

LinkedList底层是双向循环链表实现的。所以插入和删除效率较高，但查询较慢。

简单看看链表的形式。

双向链表

//模拟单向链表package com.test.list;public class NoteTest{public static void main(String[] args){Note note1 = new Note("note1");Note note2 = new Note("note2");Note note3 = new Note("note3");note1.next = note2;note2.next = note3;//显示note3的数据System.out.println(note1.next.next.data);// 新生成一个note4，将其插入到note1和note2的中间Note note4 = new Note("note4");note1.next = note4;note4.next = note2;//显示note3的数据System.out.println(note1.next.next.next.data);//将note4删除note1.next = note2;note4.next = null;//显示note3的数据System.out.println(note1.next.next.data);}}class Note{String data; //存放节点数据本身Note next;   //存放指向下一个节点的引用public Note(String data){this.data = data;}}

//模拟双向循环链表package com.test.list;public class NoteTest2{public static void main(String[] args){DoubleNote note1= new DoubleNote("note1");DoubleNote note2= new DoubleNote("note2");DoubleNote note3= new DoubleNote("note3");note1.next = note2;note2.previous = note1;note2.next = note3;note3.previous = note2;note3.next = note1;note1.previous = note3;//添加note4，并将其插在note1和note2之间DoubleNote note4 = new DoubleNote("note4");note1.next = note4;note4.previous = note1;note4.next = note2;note2.previous = note4;//将note4删除note1.next = note2;note2.previous = note1;note4.next = null;note4.previous = null;//显示note1的数据System.out.println(note1.next.next.next.data);}}class DoubleNote{DoubleNote previous;//前趋节点String data; //数据本省DoubleNote next; //后继节点public DoubleNote(String data){this.data = data;}}

LikedList的一些特有方法，例如addFirst(), removeFirst()等。

 

//使用LinkedList的方法模拟队列。package com.test.list;import java.util.LinkedList;public class LinkedListDemo1{public static void main(String[] args){MyQueue queue = new MyQueue();queue.put("First");queue.put("Second");queue.put("Third");//返回FirstSystem.out.println(queue.get()); //返回SecondSystem.out.println(queue.get()); //返回falseSystem.out.println(queue.isEmpty());}}class MyQueue{private LinkedList list = new LinkedList();public void put(Object obj){list.addLast(obj);}public Object get(){return list.removeFirst();}public boolean isEmpty(){return list.isEmpty();}}

//使用LinkedList的方法模拟栈package com.test.list;import java.util.LinkedList;import java.util.List;public class LinkedListDemo2{public static void main(String[] args){MyStack stack = new MyStack();stack.push("One");stack.push("Two");stack.push("Three");stack.push("four");for(int i = 0; i < 4 ;i++){System.out.println(stack.size());System.out.println(stack.pop());}}}class MyStack{private LinkedList list = new LinkedList();public void push(Object obj){//入栈list.addFirst(obj);}public Object pop(){// 出栈,指从栈顶删除该元素并返回return list.removeFirst();}public Object peek(){// 查看栈顶元素return list.getFirst();}public int size(){return list.size();}}