准备数据

 ArrayList<Integer> list = new ArrayList<Integer>();
 for (int i = 0; i < 100000000; i++) {
     list.add(i);
}

1.for循环

 for (int i = 0; i < list.size(); i++) {
     Integer str = list.get(i);
}

2.for-each循环

 for (Integer vo:list
        ) {

        }

3.Lambda

 list.forEach(u->{});

迭代器

Iterator<Integer> itr = list.iterator();
        while(itr.hasNext()){
            Integer str = itr.next();
        }

for循环耗时106毫秒，for-each循环耗时103毫秒，Lambda耗时122毫秒，迭代器耗时100毫秒
从结果看出，for循环、for-each循环、迭代器差不多，Lambda耗时最长