Java中LinkedList与ArrayList遍历速度比较

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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！