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！