复制代码/*建库*/
create database testdb6;
use testdb6;
/* 用户表 */
drop table if exists users;
create table users(
	id int primary key auto_increment,
	name varchar(20)
);
insert into users(name) values ('A');
insert into users(name) values ('B');
insert into users(name) values ('C');
insert into users(name) values ('D');
insert into users(name) values ('E');
insert into users(name) values ('F');
insert into users(name) values ('G');
insert into users(name) values ('H');
insert into users(name) values ('I');
insert into users(name) values ('J');

/* 订单表 */
drop table if exists orders;
create table orders(
	id int primary key auto_increment,/*订单id*/
	order_no varchar(20) not null,/*订单编号*/
	title varchar(20) not null,/*订单标题*/
	goods_num int not null,/*订单数量*/
	money decimal(7,4) not null,/*订单金额*/
	user_id int not null    /*订单所属用户id*/
)engine=myisam default charset=utf8 ;

delimiter ?
drop procedure batch_orders ?

/* 存储过程 */
create procedure batch_orders(in max int)
begin
declare start int default 0;
declare i int default 0;
set autocommit = 0;  
while i < max do
   set i = i + 1;
   insert into orders(order_no,title,goods_num,money,user_id) 
   values (concat('NCS-',floor(1 + rand()*1000000000000 )),concat('订单title-',i),i%50,(100.0000+(i%50)),i%10);
 &emsp; end while;
commit;
end ?
delimiter ;

/*插入1000万条订单数据*/
call batch_orders(10000000);     /*插入数据的过程根据机器的性能 花费的时间不同，有的可能3分钟，有的可能10分钟*/

复制代码select count(1) from orders o where o.user_id in(select u.id from users u);
select count(1) from orders o where exists (select 1 from users u where u.id = o.user_id);

复制代码1. 将文件保存到一个事先定义好的目录；如果目录不存在则新建
2. 使用excel处理工具根据文件路径读取文件内容之后处理业务逻辑
3. 编写一个定时任务每天凌晨1点删除该目录内的.xlsx文件

复制代码public class TemporaryFileExample
{
   public static void main(String[] args)
   {
      File temp;
      try
      {
         temp = File.createTempFile("myTempFile", ".txt");
          
         System.out.println("Temp file created : " + temp.getAbsolutePath());
      } catch (IOException e)
      {
         e.printStackTrace();
      }
   }
}

复制代码public class TemporaryFileExample
{
   public static void main(String[] args)
   {
      try
      {
         final Path path = Files.createTempFile("myTempFile", ".txt");
         System.out.println("Temp file : " + path);

          
      } catch (IOException e)
      {
         e.printStackTrace();
      }
   }
}

复制代码import java.io.BufferedWriter;
import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
 
public class TemporaryFileExample
{
   public static void main(String[] args)
   {
      File temp;
      try
      {
         temp = File.createTempFile("myTempFile", ".txt");
 
         BufferedWriter bw = new BufferedWriter(new FileWriter(temp));
         bw.write("This is the temporary data written to temp file");
         bw.close();
 
         System.out.println("Written to Temp file : " + temp.getAbsolutePath());
      } catch (IOException e)
      {
         e.printStackTrace();
      }
   }
}

复制代码public class TemporaryFileExample
{
   public static void main(String[] args)
   {
      try
      {
         final Path path = Files.createTempFile("myTempFile", ".txt");
         System.out.println("Temp file : " + path);
 
 
         byte[] buf = "some data".getBytes();
         Files.write(path, buf);
 
      } catch (IOException e)
      {
         e.printStackTrace();
      }
   }
}

复制代码File temp = File.createTempFile("myTempFile", ".txt");
temp.deleteOnExit();

复制代码File temp = File.createTempFile("myTempFile", ".txt");
temp.delete();

复制代码import java.io.File;
import java.io.IOException;
 
public class TemporaryFileExample
{
   public static void main(String[] args)
   {
      File temp;
      try
      {
         temp = File.createTempFile("myTempFile", ".txt");
          
         System.out.println("Temp file created : " + temp.getAbsolutePath());
          
         //temp.delete(); //立即删除
          
         temp.deleteOnExit(); //运行结束时删除
          
         System.out.println("Temp file exists : " + temp.exists());
      } catch (IOException e)
      {
         e.printStackTrace();
      }
   }
}

复制代码public class TemporaryFileExample
{
   public static void main(String[] args)
   {
      try
      {
         final Path path = Files.createTempFile("myTempFile", ".txt");
         System.out.println("Temp file : " + path);
 
        // Files.delete(path);  //立即删除文件
        
        Files.deleteIfExists(path);
          
         
          
      } catch (IOException e)
      {
         e.printStackTrace();
      }
   }
}

复制代码//可能版本不一样哦
implementation 'com.android.support.constraint:constraint-layout:1.1.3

复制代码<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout 
    ...>
    <TextView
            ...
            android:text="Hello"
            android:id="@+id/tvHello"/>

    <TextView
            ...
            android:text="World"
            app:layout_constraintLeft_toRightOf="@+id/tvHello"/>

    <TextView
            ...
            android:text="GitCode"
            app:layout_constraintTop_toBottomOf="@id/tvHello"/>
</android.support.constraint.ConstraintLayout>

复制代码<TextView
   ...
    android:text="Hello"
    android:id="@+id/tvHello"/>

<TextView
    ...
    android:text="World"
    app:layout_constraintBaseline_toBaselineOf="@id/tvHello"
    app:layout_constraintLeft_toRightOf="@+id/tvHello"/>

复制代码<TextView
        ...
        android:layout_marginTop="10dp"
        android:layout_marginLeft="10dp"/>

复制代码<TextView
        ...
        android:layout_marginTop="10dp"
        android:layout_marginLeft="10dp"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintTop_toTopOf="parent"
         />

复制代码<TextView
    ...
    android:text="Hello"
    app:layout_constraintLeft_toLeftOf="parent"
    app:layout_constraintRight_toRightOf="parent"/>

复制代码<TextView
    ...
    android:text="Hello"
    app:layout_constraintHorizontal_bias="0.8"
    app:layout_constraintLeft_toLeftOf="parent"
    app:layout_constraintRight_toRightOf="parent"/>

复制代码<TextView
    ...
    android:text="Hello"
    android:id="@+id/tvHello"
    app:layout_constraintTop_toTopOf="parent"
    app:layout_constraintBottom_toBottomOf="parent"
    app:layout_constraintLeft_toLeftOf="parent"
    app:layout_constraintRight_toRightOf="parent"/>

<TextView
    android:text="World"
    app:layout_constraintCircle="@id/tvHello"
    app:layout_constraintCircleRadius="180dp"
    app:layout_constraintCircleAngle="135"/>

复制代码 <TextView
        android:text="Hello"
        android:id="@+id/tvHello"
        android:gravity="center"
        android:padding="20dp"
        app:layout_constraintTop_toTopOf="parent"
        android:textColor="@color/colorWhite"
        android:background="@color/colorPrimary"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        android:layout_width="0dp"
        android:layout_marginRight="20dp"
        android:layout_height="wrap_content"/>

复制代码<TextView
        android:text="Hello"
        android:id="@+id/tvHello"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintWidth_percent="0.5"
        app:layout_constraintWidth_default="percent"
        android:layout_width="0dp"
        android:layout_height="wrap_content"/>

复制代码<TextView
    android:text="Hello"
    app:layout_constraintDimensionRatio="3:1"
    android:layout_width="0dp"
    android:layout_height="100dp"
    />

复制代码<Button android:layout_width="0dp" android:layout_height="0dp"
    app:layout_constraintDimensionRatio="H,16:9"
    app:layout_constraintBottom_toBottomOf="parent"
    app:layout_constraintTop_toTopOf="parent"/>

复制代码<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
    
    <TextView
            android:text="Hello"
            android:id="@+id/tvHello"
            android:gravity="center"
            android:padding="20dp"
            app:layout_constraintHorizontal_chainStyle="spread"
            app:layout_constraintLeft_toLeftOf="parent"
            app:layout_constraintRight_toLeftOf="@id/tvWorld"
            android:textColor="@color/colorWhite"
            android:background="@color/colorPrimaryDark"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"/>
    <TextView
            android:text="World"
            android:gravity="center"
            android:padding="20dp"
            android:id="@+id/tvWorld"
            app:layout_constraintLeft_toRightOf="@id/tvHello"
            app:layout_constraintRight_toRightOf="parent"
            android:textColor="@color/colorWhite"
            android:background="@color/colorPrimary"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"/>
    
</android.support.constraint.ConstraintLayout>

复制代码<android.support.constraint.ConstraintLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
    
    <android.support.constraint.Guideline
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:id="@+id/guideline"
            android:orientation="vertical"
            app:layout_constraintGuide_begin="10dp"/>

    <Button android:text="Button"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:id="@+id/button"
            app:layout_constraintLeft_toLeftOf="@+id/guideline"
            android:layout_marginTop="16dp"
            app:layout_constraintTop_toTopOf="parent"/>

    <Button android:text="Button2"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:id="@+id/button2"
            app:layout_constraintLeft_toLeftOf="@+id/guideline"
            android:layout_marginTop="16dp"
            app:layout_constraintTop_toBottomOf="@id/button"/>
</android.support.constraint.ConstraintLayout>

复制代码<android.support.constraint.ConstraintLayout
        xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:app="http://schemas.android.com/apk/res-auto"
        android:layout_width="match_parent"
        android:layout_height="match_parent">

    <android.support.constraint.Barrier
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            app:barrierDirection="right"
            android:id="@+id/barrier"
            app:constraint_referenced_ids="tvPhone,tvPassword"
            />

    <TextView android:layout_width="wrap_content"
              android:text="手机号码"
              android:id="@+id/tvPhone"
              android:gravity="center_vertical|left"
              android:padding="10dp"
              android:layout_height="50dp"/>

    <TextView android:layout_width="wrap_content"
              android:text="密码"
              android:padding="10dp"
              android:gravity="center_vertical|left"
              android:id="@+id/tvPassword"
              app:layout_constraintTop_toBottomOf="@id/tvPhone"
              android:layout_height="wrap_content"/>

    <EditText android:layout_width="wrap_content"
              android:hint="输入手机号码"
              android:id="@+id/etPassword"
              app:layout_constraintLeft_toLeftOf="@id/barrier"
              android:layout_height="wrap_content"/>

    <EditText android:layout_width="wrap_content"
              android:hint="输入密码"
              app:layout_constraintTop_toBottomOf="@id/etPassword"
              app:layout_constraintLeft_toLeftOf="@id/barrier"
              android:layout_height="wrap_content"/>


</android.support.constraint.ConstraintLayout>

复制代码<android.support.constraint.ConstraintLayout
        xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:app="http://schemas.android.com/apk/res-auto"
        android:layout_width="match_parent"
        android:layout_height="match_parent">

    <android.support.constraint.Group
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:id="@+id/group"
            android:visibility="gone"
            app:constraint_referenced_ids="tvPhone,tvPassword"
            />

    <TextView android:layout_width="wrap_content"
              android:text="手机号码"
              android:id="@+id/tvPhone"
              android:gravity="center_vertical|left"
              android:padding="10dp"
              android:layout_height="50dp"/>

    <TextView android:layout_width="wrap_content"
              android:text="密码"
              android:padding="10dp"
              android:gravity="center_vertical|left"
              android:id="@+id/tvPassword"
              app:layout_constraintLeft_toRightOf="@id/tvPhone"
              app:layout_constraintTop_toBottomOf="@id/tvPhone"
              android:layout_height="wrap_content"/>

    <TextView android:layout_width="wrap_content"
              android:text="GitCode"
              android:padding="10dp"
              android:gravity="center_vertical|left"
              app:layout_constraintLeft_toRightOf="@id/tvPassword"
              android:layout_height="wrap_content"/>

</android.support.constraint.ConstraintLayout>

复制代码<android.support.constraint.ConstraintLayout
        xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:app="http://schemas.android.com/apk/res-auto"
        android:layout_width="match_parent"
        android:layout_height="match_parent">

    <android.support.constraint.Placeholder
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            app:content="@id/tvGitCode"
              />
    
    <TextView android:layout_width="wrap_content"
              android:text="GitCode"
              android:id="@+id/tvGitCode"
              android:padding="10dp"
              app:layout_constraintLeft_toLeftOf="parent"
              app:layout_constraintRight_toRightOf="parent"
              android:gravity="center_vertical|left"
              android:layout_height="wrap_content"/>

</android.support.constraint.ConstraintLayout>

复制代码public class DemoMain {

    public static void main(String[] args) throws Exception {
        Config config = new Config();
        config.useSingleServer().setAddress("redis://127.0.0.1:6379");

        RedissonClient redisson = Redisson.create(config);
        RLock lock = redisson.getLock("anyLock");

        lock.lock();
        //lock.unlock();
    }
}

复制代码public class Config {
	
	private long lockWatchdogTimeout = 30 * 1000;
		
	public long getLockWatchdogTimeout() {
		return lockWatchdogTimeout;
	}
	
	//省略无关代码
}

复制代码public  Bitmap convertViewToBitmap(View view){
    view.destroyDrawingCache();//销毁旧的cache销毁，获取cache通常会占用一定的内存，所以通常不需要的时候有必要对其进行清理
    view.setDrawingCacheEnabled(true);//cache开启
    view.buildDrawingCache();//创建新的缓存,获取cache通常会占用一定的内存，所以通常不需要的时候有必要对其进行清理,在每次获取新的,先销毁旧的缓存
    view.measure(View.MeasureSpec.makeMeasureSpec(0, View.MeasureSpec.UNSPECIFIED), View.MeasureSpec.makeMeasureSpec(0, View.MeasureSpec.UNSPECIFIED));//测量view
    Bitmap bitmap = Bitmap.createBitmap(view.getDrawingCache());//将缓存的view转换为图片
    return bitmap;
}

复制代码/**
 * 视频截图代码
 * @param url   播放的url
 * @param width 生成图片的宽度
 * @param height    生成图片的高度
 * @param currentVideoTime  当前播放的播放的秒数
 * @return
 */
@TargetApi(Build.VERSION_CODES.ICE_CREAM_SANDWICH)
private Bitmap createVideoThumbnail(String url, int width, int height,String currentVideoTime) {
    Bitmap bitmap = null;
    MediaMetadataRetriever retriever = new MediaMetadataRetriever();
    int kind = MediaStore.Video.Thumbnails.MINI_KIND;
    try {
        if (Build.VERSION.SDK_INT >= 14) {//Android4.0以上的设备,必须使用这种方式来设置源播放视频的路径
            retriever.setDataSource(url, new HashMap<String, String>());
        } else {
            retriever.setDataSource(url);
        }
        int millis = mMdeiaPlayer.getDuration();
        Log.e(TAG, "-----millis----" + millis);
        int pro = mMdeiaPlayer.getCurrentPosition();
        Log.e(TAG,"-----pro----"+pro);
        String timeString = retriever.extractMetadata(MediaMetadataRetriever.METADATA_KEY_DURATION);
        long time = Long.parseLong(timeString) * 1000; //获取总长度,这一句也是必须的
        long d = time*pro/millis;//计算当前播放的帧数,来截取当前的视频
        Log.e(TAG,"---------"+d);
        bitmap = retriever.getFrameAtTime(d, MediaMetadataRetriever.OPTION_CLOSEST_SYNC);
        if (kind == MediaStore.Images.Thumbnails.MICRO_KIND && bitmap != null) {
            bitmap = ThumbnailUtils.extractThumbnail(bitmap, width, height,
                    ThumbnailUtils.OPTIONS_RECYCLE_INPUT);
        }
    } catch (IllegalArgumentException ex) {
        // Assume this is a corrupt video file
    } catch (RuntimeException ex) {
        // Assume this is a corrupt video file.
    } finally {
        try {
            retriever.release();
            mMdeiaPlayer.start();
        } catch (RuntimeException ex) {
            // Ignore failures while cleaning up.
        }
    }

    return bitmap;
}

复制代码04-05 10:58:14.169 2237-2237/demo.dhl.con.onlinevideo E/MediaPlayer: start called in state 4
04-05 10:58:14.169 2237-2237/demo.dhl.con.onlinevideo E/MediaPlayer: error (-38, 0)
04-05 10:58:14.169 2237-2237/demo.dhl.con.onlinevideo E/MediaPlayer: Error (-38,0)
04-05 10:58:14.176 2237-2250/demo.dhl.con.onlinevideo E/MediaPlayer: error (261, -1003)
04-05 10:58:14.176 2237-2237/demo.dhl.con.onlinevideo E/MediaPlayer: Error (261,-1003)

复制代码04-05 11:50:27.346 2038-2038/demo.dhl.con.onlinevideo E/MediaPlayer: start called in state 1
04-05 11:50:27.347 2038-2038/demo.dhl.con.onlinevideo E/MediaPlayer: error (-38, 0)
04-05 11:50:27.367 2038-2050/demo.dhl.con.onlinevideo E/MediaPlayer: error (261, -1003)
04-05 11:50:27.367 2038-2038/demo.dhl.con.onlinevideo E/MediaPlayer: Error (261,-1003)

复制代码Streaming is Not supported before Android 3.0
Please test in device having above 3.0 version

复制代码![](http://upload-images.jianshu.io/upload_images/1479838-d821c0b136e94734.jpg?imageMogr2/auto-orient/strip%7CimageView2/2/w/1240)
这是Android官网关于，Android所支持的网络协议网络协议
>音频和视频播放支持以下网络协议：
>RTSP协议（RTP，SDP的）
>HTTP / HTTPS的进步流
>HTTP / HTTPS的现场直播议定书草案：
>MPEG-2 TS流媒体文件只
>协议版本3（的Android 4.0及以上）
>议定书“第2版（Android的3.x版）
>不支持之前的Android 3.0
>注： HTTPS不支持之前的Android 3.1。
更换一台Android3.0以上的设备就好了

复制代码java.io.IOException: setDataSource failed.: status=0x80000000

复制代码InputStream in = getResources().getAssets().open("GPSResp.dat");

复制代码static const char* kNoCompressExt[] = {
    ".jpg", ".jpeg", ".png", ".gif",
    ".wav", ".mp2", ".mp3", ".ogg", ".aac",
    ".mpg", ".mpeg", ".mid", ".midi", ".smf", ".jet",
    ".rtttl", ".imy", ".xmf", ".mp4", ".m4a",
    ".m4v", ".3gp", ".3gpp", ".3g2", ".3gpp2",
    ".amr", ".awb", ".wma", ".wmv"
};

复制代码    java.io.IOException: Prepare failed.: status=0x1

复制代码    getFrameAtTime: videoFrame is a NULL pointer

复制代码    12:58:24.690: E/BaseSurfaceHolder(719): Exception locking surface
    12:58:24.690: E/BaseSurfaceHolder(719): java.lang.IllegalArgumentException
    12:58:24.690: E/BaseSurfaceHolder(719):   at android.view.Surface.nativeLockCanvas(Native Method)
    12:58:24.690: E/BaseSurfaceHolder(719):   at android.view.Surface.lockCanvas(Surface.java:447)
    12:58:24.690: E/BaseSurfaceHolder(719):   at com.android.internal.view.BaseSurfaceHolder.internalLockCanvas(BaseSurfaceHolder.java:184)

复制代码public static void main(String[] args) {
    List<String> names = new ArrayList<String>() {{
        add("Hollis");
        add("hollischuang");
        add("H");
    }};

    List subList = names.subList(0, 1);
    System.out.println(subList);
}

复制代码[Hollis]

复制代码public static void main(String[] args) {
    List<String> names = new ArrayList<String>() {{
        add("Hollis");
        add("hollischuang");
        add("H");
    }};

    ArrayList subList = names.subList(0, 1);
    System.out.println(subList);
}

复制代码java.lang.ClassCastException: java.util.ArrayList$SubList cannot be cast to java.util.ArrayList

复制代码public List<E> subList(int fromIndex, int toIndex) {
    subListRangeCheck(fromIndex, toIndex, size);
    return new SubList(this, 0, fromIndex, toIndex);
}

复制代码SubList(AbstractList<E> parent,
            int offset, int fromIndex, int toIndex) {
    this.parent = parent;
    this.parentOffset = fromIndex;
    this.offset = offset + fromIndex;
    this.size = toIndex - fromIndex;
    this.modCount = ArrayList.this.modCount;
}

复制代码public static void main(String[] args) {
    List<String> sourceList = new ArrayList<String>() {{
        add("H");
        add("O");
        add("L");
        add("L");
        add("I");
        add("S");
    }};

    List subList = sourceList.subList(2, 5);

    System.out.println("sourceList ： " + sourceList);
    System.out.println("sourceList.subList(2, 5) 得到List ：");
    System.out.println("subList ： " + subList);

    subList.set(1, "666");

    System.out.println("subList.set(3,666) 得到List ：");
    System.out.println("subList ： " + subList);
    System.out.println("sourceList ： " + sourceList);

}

复制代码sourceList ： [H, O, L, L, I, S]
sourceList.subList(2, 5) 得到List ：
subList ： [L, L, I]
subList.set(3,666) 得到List ：
subList ： [L, 666, I]
sourceList ： [H, O, L, 666, I, S]

复制代码public static void main(String[] args) {
    List<String> sourceList = new ArrayList<String>() {{
        add("H");
        add("O");
        add("L");
        add("L");
        add("I");
        add("S");
    }};

    List subList = sourceList.subList(2, 5);

    System.out.println("sourceList ： " + sourceList);
    System.out.println("sourceList.subList(2, 5) 得到List ：");
    System.out.println("subList ： " + subList);

    subList.add("666");

    System.out.println("subList.add(666) 得到List ：");
    System.out.println("subList ： " + subList);
    System.out.println("sourceList ： " + sourceList);

}

复制代码sourceList ： [H, O, L, L, I, S]
sourceList.subList(2, 5) 得到List ：
subList ： [L, L, I]
subList.add(666) 得到List ：
subList ： [L, L, I, 666]
sourceList ： [H, O, L, L, I, 666, S]

复制代码public static void main(String[] args) {
    List<String> sourceList = new ArrayList<String>() {{
        add("H");
        add("O");
        add("L");
        add("L");
        add("I");
        add("S");
    }};

    List subList = sourceList.subList(2, 5);

    System.out.println("sourceList ： " + sourceList);
    System.out.println("sourceList.subList(2, 5) 得到List ：");
    System.out.println("subList ： " + subList);

    sourceList.add("666");

    System.out.println("sourceList.add(666) 得到List ：");
    System.out.println("sourceList ： " + sourceList);
    System.out.println("subList ： " + subList);

}

复制代码Exception in thread "main" java.util.ConcurrentModificationException
    at java.util.ArrayList$SubList.checkForComodification(ArrayList.java:1239)
    at java.util.ArrayList$SubList.listIterator(ArrayList.java:1099)
    at java.util.AbstractList.listIterator(AbstractList.java:299)
    at java.util.ArrayList$SubList.iterator(ArrayList.java:1095)
    at java.util.AbstractCollection.toString(AbstractCollection.java:454)
    at java.lang.String.valueOf(String.java:2994)
    at java.lang.StringBuilder.append(StringBuilder.java:131)
    at com.hollis.SubListTest.main(SubListTest.java:28)

复制代码subList = Lists.newArrayList(subList);
list.stream().skip(strart).limit(end).collect(Collectors.toList());

复制代码//为了考虑大多数同学学习过Java,就贴Java的代码
//定义个监听类，用来在Activity生命周期发生变化时，对定位服务资源作相关处理
class MyLocationListener {
    public MyLocationListener(Context context, Callback callback) {
        // ...
    }

    void start() {
        // connect to system location service
    }

    void stop() {
        // disconnect from system location service
    }
}
//在Activity中回调监听类相关方法
class MyActivity extends AppCompatActivity {
    private MyLocationListener myLocationListener;

    @Override
    public void onCreate(...) {
        myLocationListener = new MyLocationListener(this, (location) -> {
            // update UI
        });
    }
    
    @Override
    public void onStart() {
        super.onStart();
        myLocationListener.start();
        // manage other components that need to respond
        // to the activity lifecycle
    }

    @Override
    public void onStop() {
        super.onStop();
        myLocationListener.stop();
        // manage other components that need to respond
        // to the activity lifecycle
    }
}

复制代码//MyObserver作为一个观察者来监听有生命周期的类
public class MyObserver implements LifecycleObserver {
    @OnLifecycleEvent(Lifecycle.Event.ON_RESUME)
    public void connectListener() {
        ...
    }

    @OnLifecycleEvent(Lifecycle.Event.ON_PAUSE)
    public void disconnectListener() {
        ...
    }
}
//myLifecycleOwner是一个实现了LifecycleOwner 接口的类，继续看下文
myLifecycleOwner.getLifecycle().addObserver(new MyObserver());

复制代码myLifecycleOwner.getLifecycle().addObserver(new MyObserver());

复制代码class MyActivity extends AppCompatActivity {
    private MyLocationListener myLocationListener;

    public void onCreate(...) {
        myLocationListener = new MyLocationListener(this, getLifecycle(), location -> {
            // update UI
        });
        Util.checkUserStatus(result -> {
            if (result) {
                myLocationListener.enable();
            }
        });
  }
}

复制代码public class MyActivity extends Activity implements LifecycleOwner {
    private LifecycleRegistry lifecycleRegistry;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        lifecycleRegistry = new LifecycleRegistry(this);
        lifecycleRegistry.markState(Lifecycle.State.CREATED);
    }

    @Override
    public void onStart() {
        super.onStart();
        lifecycleRegistry.markState(Lifecycle.State.STARTED);
    }

    @NonNull
    @Override
    public Lifecycle getLifecycle() {
        return lifecycleRegistry;
    }
}