java list三种遍历方法性能比较

public static void compare() {
    List<String> list = new ArrayList<String>();
 Set<String> set = new HashSet<String>();
for(int i=0;i<100000;i++) {
 list.add("a"+i);
 }
long t1=0L,t2=0L;
 t1 = System.currentTimeMillis();
for(String s : list) {
 set.add(s);
 }
 t2 = System.currentTimeMillis();
 System.out.println("forEach遍历的时间为："+(t2-t1)+"mm");
////two
 t1 = System.currentTimeMillis();
for(int i=0; i<list.size(); i++) {
 String str = list.get(i);
 set.add(list.get(i));
 }
 t2 = System.currentTimeMillis();
 System.out.println("size遍历的时间为："+(t2-t1)+"mm");
////three
 t1 = System.currentTimeMillis();
 Iterator<String> iterator = list.iterator();
while(iterator.hasNext()) {
 String str = iterator.next();
 set.add((String)iterator.next());
 }
 t2 = System.currentTimeMillis();
 System.out.println("iterator遍历的时间为："+(t2-t1)+"mm");
}

forEach遍历的时间为：45mm
size遍历的时间为：14mm
iterator遍历的时间为：7mm