ArrayList与LinkedList都是继承至Collection对象,内部实现导致性能方面存在一定的区别

插入性能对比

private final static int COUNT = 10000000;private static long insertObject(List<Object> list) { Object obj = new Object(); long startTime = System.currentTimeMillis(); for (int i = 0; i < COUNT; i++) { list.add(obj); } long endTime = System.currentTimeMillis(); return endTime - startTime;}public static void main(String[] args) { int initCount = (int) (COUNT * 1.5); System.out.println("ArrayList 增加" + COUNT + "条数据,耗时:" + insertObject(new ArrayList<Object>(initCount))); System.out.println("LinkedList 增加" + COUNT + "条数据,耗时:" + insertObject(new LinkedList<Object>()));}

上述代码得出下列结果:

private final static int COUNT = 1000000; private static Map<String, Object> insertObject(List<Object> list) { User user = new User(); long startTime = System.currentTimeMillis(); for (int i = 0; i < COUNT; i++) { user.setId(i); user.setName("i:" + i); user.setAge(i); list.add(user); } long endTime = System.currentTimeMillis(); Map result = new HashMap<String, Object>(); result.put("time", endTime - startTime); result.put("list", list); return result; } private static long readObject(List<User> list) { long startTime = System.currentTimeMillis(); for (User user : list) { } long endTime = System.currentTimeMillis(); return endTime - startTime; } public static void main(String[] args) { // 插入 int initCount = (int) (COUNT * 1.5); Map<String, Object> arrayListResult = insertObject(new ArrayList<Object>()); Map<String, Object> linkedListResult = insertObject(new LinkedList<Object>()); System.out.println("ArrayList 增加" + COUNT + "条数据,耗时:" + arrayListResult.get("time")); System.out.println("LinkedList 增加" + COUNT + "条数据,耗时:" + linkedListResult.get("time")); // 读取 System.out.println("ArrayList 查询" + COUNT + "条数据,耗时:" + readObject((List<User>) arrayListResult.get("list"))); System.out.println("LinkedList 查询" + COUNT + "条数据,耗时:" + readObject((List<User>) linkedListResult.get("list"))); }

结果如下所示:

3.LinkedList的优势

static final int N = 500000; static long timeList(List<Object> list) { long start = System.currentTimeMillis(); Object o = new Object(); for (int i = 0; i < N; i++) { list.add(0, o); } long endTime = System.currentTimeMillis(); return endTime - start; } static long readList(List list) { long start = System.currentTimeMillis(); for (int i = 0, j = list.size(); i < j; i++) { } return System.currentTimeMillis() - start; } static List addList(List list) { Object o = new Object(); for (int i = 0; i < N; i++) { list.add(0, o); } return list; } public static void main(String[] args) { System.out.println("ArrayList添加" + N + "条耗时：" + timeList(new ArrayList<Object>())); System.out.println("LinkedList添加" + N + "条耗时：" + timeList(new LinkedList<Object>())); List list1 = addList(new ArrayList<>()); List list2 = addList(new LinkedList<>()); System.out.println("ArrayList查找" + N + "条耗时：" + readList(list1)); System.out.println("LinkedList查找" + N + "条耗时：" + readList(list2)); }

结果:

LinkedList的优势在于头部插入,而不是随机插入,在使用过程中需要根据自己的需求进行选择!!!