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
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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!!!
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