Java中LinkedList与ArrayList遍历速度比较，

Java中LinkedList与ArrayList遍历速度比较，

import java.util.LinkedList;  
import java.util.ArrayList;  
import java.util.Random;

public class testList {
  private static Random random = new Random();  
  public static void main(String[] args){  
    ArrayList<String> arraylist = new ArrayList<String>();  
    LinkedList<String> linkedlist = new LinkedList<String>();  
    for(int i=0;i<50000;i++){  
      String r = randomString();  
      arraylist.add(r);  
      linkedlist.add(r);  
    }  
    
    System.out.println("arraylist size "+arraylist.size());  
    System.out.println("linkedlist size "+linkedlist.size());  
    System.out.println("------");  
    long begin = System.currentTimeMillis();  
    for(int i=0;i<100;i++){  
      int size = arraylist.size();
      for(int j=0;j<size;j++){  
        String s=arraylist.get(j);  
      }  
    }  
    System.out.println("arraylist get(n) time "+(System.currentTimeMillis()-begin));  
    
    begin = System.currentTimeMillis();  
    for(int i=0;i<100;i++){  
      for(String s:arraylist){  
      }  
    }  
    System.out.println("arraylist foreach time "+(System.currentTimeMillis()-begin));  
    
    begin = System.currentTimeMillis();  
    for(int i=0;i<1;i++){
      int size = linkedlist.size();
      for(int j=0; j<size; j++){  
        String s=linkedlist.get(j);  
      }  
    }
    System.out.println("linkedlist get(n) time "+(System.currentTimeMillis()-begin)*100);  
    
    begin = System.currentTimeMillis();  
    for(int i=0;i<100;i++)  
      for(String s:linkedlist){  
      }  
    System.out.println("linkedlist foreach time "+(System.currentTimeMillis()-begin));  
  }  
  
  protected static String randomString() {  
    return Long.toString(random.nextLong(), 36);  
  }  
}

arraylist size 50000
linkedlist size 50000
------
arraylist get(n) time 47
arraylist foreach time 188
linkedlist get(n) time 215600
linkedlist foreach time 94

可以看到：

对于ArrayList，用get(i)遍历比用foreach快！

对于LinkedList，用get(i)遍历相当慢，用foreach比get(i)快！

因此对于遍历一个List，用arrayList的get(i)遍历是最快的！