List介紹

List 實現了collection接口

ArrayList

1. 以數組實現的列表，不支持同步
2. 利用索引位置可以快速定位訪問
3. 不適合指定位置的插入、刪除操作
4. 適合變動不大的，主要用於查詢的數據
5. 和java數組相比，其容量是可以動態調整的
6. ArrayList在元素填滿容器的時會自動擴充容器大小的50% 

import java.util.ArrayList;
import java.util.Iterator;

public class ArrayList_test {

	public static void main(String[] args) {

		ArrayList<Integer> al=new ArrayList<Integer>();
		al.add(3);
		al.add(2);
		al.add(1);
		al.add(4);
		al.add(5);
		al.add(6);
		al.add(new Integer(6));
		
		System.out.println("This third element is ");
		System.out.println(al.get(3));
		al.remove(3);
		al.add(3,9);
		System.out.println("==================遍歷方法=================");
		
		ArrayList<Integer>  al2=new ArrayList<Integer>(100000);
		for(int i=0;i<100000;i++){
			al2.add(i);
		}
		
		traverByIterator(al2); 
		traverByIndex(al2);
		traverByFor(al2);
		
	}
	public static void traverByIterator(ArrayList<Integer> al){
		System.out.println("迭代器遍歷---------------");
		long startTime = System.nanoTime();	
		Iterator iter=al.iterator();	
		while(iter.hasNext()){
			iter.next();
		}
		long endTime =System.nanoTime();
		long duration=endTime-startTime;
		System.out.println(duration+"納秒");
	}
	
	public static void traverByIndex(ArrayList<Integer> al){
		System.out.println("索引位置遍歷---------------");

		long startTime = System.nanoTime();	
		for(int i=0;i<al.size();i++){
			al.get(i);
		} 
		
		long endTime =System.nanoTime();
		long duration=endTime-startTime;
		System.out.println(duration+"納秒");
	}
	public static void traverByFor(ArrayList<Integer> al){
		System.out.println("索引位置遍歷---------------");

		long startTime = System.nanoTime();	
		 
		for(Integer item:al){
			;
		}
		
		long endTime =System.nanoTime();
		long duration=endTime-startTime;
		System.out.println(duration+"納秒");
	}
}

ArrayLIist在使用迭代器遍歷的時候速度最慢

———————————————————————————————————————————————————

LinkedList

1. 以雙向鏈表實現的列表，不支持同步
2. 可被當作堆棧、隊列和雙端隊列進行操作
3. 順序訪問高效，隨機訪問較差，中間插入和刪除高效
4. 適用於經常變化的數據

import java.util.*;
import java.util.Iterator;

public class LinkedList_test {

	public static void main(String[] args) {

		LinkedList<Integer> al=new LinkedList<Integer>();
		al.add(3);
		al.add(2);
		al.add(1);
		al.add(4);
		al.add(5);
		al.add(6);
		
 		System.out.println(al.size());
 		al.addFirst(9);
		al.add(3,9);
		al.remove(3);

		System.out.println("==================遍歷方法=================");
		
		LinkedList<Integer>  al2=new LinkedList<Integer>();
		for(int i=0;i<100000;i++){
			al2.add(i);
		}
		
		traverByIterator(al2); 
		traverByIndex(al2);
		traverByFor(al2);
		
	}
	public static void traverByIterator(LinkedList<Integer> al){
		System.out.println("迭代器遍歷---------------");
		long startTime = System.nanoTime();	
		Iterator iter=al.iterator();	
		while(iter.hasNext()){
			iter.next();
		}
		long endTime =System.nanoTime();
		long duration=endTime-startTime;
		System.out.println(duration+"納秒");
	}
	
	public static void traverByIndex(LinkedList<Integer> al){
		System.out.println("索引位置遍歷---------------");

		long startTime = System.nanoTime();	
		for(int i=0;i<al.size();i++){
			al.get(i);
		} 
		
		long endTime =System.nanoTime();
		long duration=endTime-startTime;
		System.out.println(duration+"納秒");
	}
	public static void traverByFor(LinkedList<Integer> al){
		System.out.println("索引位置遍歷---------------");

		long startTime = System.nanoTime();	
		 
		for(Integer item:al){
			;
		}
		
		long endTime =System.nanoTime();
		long duration=endTime-startTime;
		System.out.println(duration+"納秒");
	}
}

LinkedList在隨機索引值遍歷最慢

——————————————————————————————————————————————————

Vector(同步)

1. 和ArrayList類似，可變數組實現的列表
2. Vector同步，適合在多線程下使用
3. 原先不屬於JCF框架，屬於java最早的數據結構，性能較差
4. 從JDK1.2開始，Vector被重寫，並納入JCF

import java.util.Vector;
import java.util.Enumeration;
import java.util.Iterator;

public class Vector_test {
	public static void main(String[] args) {
		
		Vector<Integer> al=new Vector<Integer>();
		al.add(3);
		al.add(2);
		al.add(1);
		al.add(4);
		al.add(5);
		al.add(6);
		al.add(new Integer(6));
		
		System.out.println("This third element is ");
		System.out.println(al.get(3));
		al.remove(3);
		al.add(3,9);
		System.out.println("==================遍歷方法=================");
		
		Vector<Integer>  al2=new Vector<Integer>(100000);
		for(int i=0;i<100000;i++){
			al2.add(i);
		}
		
		traverByIterator(al2); 
		traverByIndex(al2);
		traverByFor(al2);
		traverByEnumeration(al2);
		
	}
	public static void traverByIterator(Vector<Integer> al){
		System.out.println("迭代器遍歷---------------");
		long startTime = System.nanoTime();	
		Iterator iter=al.iterator();	
		while(iter.hasNext()){
			iter.next();
		}
		long endTime =System.nanoTime();
		long duration=endTime-startTime;
		System.out.println(duration+"納秒");
	}
	
	public static void traverByIndex(Vector<Integer> al){
		System.out.println("索引位置遍歷---------------");

		long startTime = System.nanoTime();	
		for(int i=0;i<al.size();i++){
			al.get(i);
		} 
		
		long endTime =System.nanoTime();
		long duration=endTime-startTime;
		System.out.println(duration+"納秒");
	}
	public static void traverByFor(Vector<Integer> al){
		System.out.println("索引位置遍歷---------------");

		long startTime = System.nanoTime();	
		 
		for(Integer item:al){
			;
		}
		
		long endTime =System.nanoTime();
		long duration=endTime-startTime;
		System.out.println(duration+"納秒");
	}
	public static void traverByEnumeration(Vector<Integer> al){
		System.out.println("Enumeration遍歷---------------");

		long startTime = System.nanoTime();	
		for(Enumeration<Integer> enu=al.elements();enu.hasMoreElements();){
			enu.nextElement();
		}
		 
		
		long endTime =System.nanoTime();
		long duration=endTime-startTime;
		System.out.println(duration+"納秒");
	}
}