@RestController
@RequestMapping(value = "/kv")
public class KeyValueController {
    ConcurrentHashMap<String,String> map = new ConcurrentHashMap<>();

    @GetMapping(value = "/{key}")
    String get(@PathVariable String key){
        return map.get(key);
    }
    @RequestMapping(value = "/{key}", method = RequestMethod.POST)
    public String put(@PathVariable String key,
                              @RequestParam(value = "value") String value) throws UnsupportedEncodingException {
        System.out.println(key + ":" +  URLDecoder.decode(value,"utf-8"));
        map.put(key,value);
        return value;
    }

}

long i = 1;
try {
	for (; ; i++) {
		byte[] bigObject = new byte[Unit];//本程序的GC基本上都是由本行代码触发
		register(bigObject);	  //使用PhantomReference跟踪bigObject的释放情况,并调用checkGC()
		if (i % 4 == 0) holder.add(bigObject);		
		if (i % 5 == 0) holder.poll();
		Thread.sleep(30);
	}

} catch (`OutOfMemoryError` error) {
	System.out.println("`OutOfMemoryError`: 一共创建bigObject:" + (i-1) + "个,GC次数:" + gcCount);
	System.out.println("总共成功回收bigObject:" + gcObjectCount + ",堆中还剩下:" + phantomSet.size());
}

static void register(byte[] bigObject){
    System.out.print(".");  //打一个点表示成功创建一个bigObject
	phantomSet.add(new PhantomReference<>(bigObject,phantomReferenceQueue));
	checkGC();
    System.out.print(".");  //打一个点表示成功创建一个bigObject
}

static void checkGC(){
	int count = 0;
	Reference<?> reference = null;
	while ((reference = phantomReferenceQueue.poll()) != null) {
		count++;
		phantomSet.remove(reference);
	}

	if(count > 0){
		System.out.println("下次GC将回收bigObject:" + count );
		gcCount++;
		gcObjectCount += count;

	}

}

ChannelInboundHandler handler = (ctx,msg) -> {
    byte[] bytes = (byte[])msg;
    String str = new String(bytes);
    System.out.println("接收到消息:" + str);
    ByteBuffer buffer = ByteBuffer.wrap(bytes);
    ctx.write(buffer).addListener((future) -> {
        System.out.println("回复成功");
    });
};
EventLoopGroup bossGroup = new NioEventLoopGroup(1);
EventLoopGroup workerGroup = new NioEventLoopGroup(1);
ServerBootstrap b = new ServerBootstrap();
b.group(bossGroup, workerGroup).channel(NioServerSocketChannel.class).childHandler(handler);
//这里改成异步调用
b.bind(6666).addListener((future)->{
    System.out.println("绑定端口成功");
});

//升级前, bind是同步操作
b.bind(6666);

//升级后,bind成为了异步操作,可以添加listener
b.bind(6666).addListener((future)->{
    System.out.println("绑定端口成功");
});

ChannelHandler handler = (o) -> {
    byte[] bytes = (byte[])o;
    String msg = new String(bytes);
    System.out.println("接收到消息:" + msg);
};
EventLoopGroup bossGroup = new NioEventLoopGroup(1);
EventLoopGroup workerGroup = new NioEventLoopGroup(1);
ServerBootstrap b = new ServerBootstrap();
b.group(bossGroup, workerGroup).channel(NioServerSocketChannel.class).childHandler(handler);
b.bind(6666);

public abstract class AbstractBootstrap<
        B extends AbstractBootstrap<B, C>, 
        C extends Channel
        >  implements Cloneable

class AbstractBootstrap<C extends Channel>

public AbstractBootstrap<C> group(EventLoopGroup group)

ServerBootstrap b = new ServerBootstrap();
b.group(bossGroup).childHandler( ...)

public B group(EventLoopGroup group)

myMap = new HashMap<String, Object>();
myMap.put("id", 5);
myMap.put("name", "xuqi");
myMap.put("age", 18);

//这个方法多了一些多余的put很令人不爽
Map<String , Object> map = new HashMap<String , Object>(){{
    put("id", 5);
    put("name", "xuqi");
    put("age", 18);
}};

static Map<String,String> createStringMap(String[][] entries){
    return Stream.of(entries).collect(Collectors.toMap(data -> data[0], data -> data[1]));
}

static Map<String,Integer> createIntegerMap(Object[][] entries){
    return Stream.of(entries).collect(Collectors.toMap(data -> (String) data[0], data -> (Integer) data[1]));
}

//创建值为String的Map
Map<String,String> stringMap = 
    createStringMap(new String[][] {{ "key1", "value1" },{ "key2", "value2" },{ "key3", "value3" }});

//创建值为Integer的Map
Map<String,Integer> intMap = 
    createIntegerMap(new Object[][] {{ "key1", 1 },{ "key2", 2 },{ "key3", 3 }});

//该方法因为类型擦除无法实现
static  <T> Map<String,T> createMap(Object[][] entries)

Map<String, String> unmodifiableMap = Map.of("key1", "value1", "key2", "value2");

public static <A> Map<String, A> asMap(Object... keysAndValues) {
    return new LinkedHashMap<String, A>() {{
        for (int i = 0; i < keysAndValues.length - 1; i++) {
            put(keysAndValues[i].toString(), (A) keysAndValues[++i]);
        }
    }};
}

Map<String, String> one = asMap("1stKey", "1stVal", "2ndKey", "2ndVal");
Map<String, Object> two = asMap("1stKey", Boolean.TRUE, "2ndKey", new Integer(2));

//混合型Map
Map<String,Object> map = hashMap(id -> 5,name -> "xuqi",age -> 18);

//String
Map<String,String> stringMap = hashMap(id -> "5",name -> "xuqi",age -> "18");

//Integer
Map<String,Integer> intMap = hashMap(id -> 5,name -> 6666,age -> 18);

Method replaceMethod = getClass().getDeclaredMethod("writeReplace");
replaceMethod.setAccessible(true);
SerializedLambda lambda= (SerializedLambda) replaceMethod.invoke(this);
Class<?> containingClass = Class.forName(lambda.getImplClass().replaceAll("/","."));
Method method = asList(containingClass.getDeclaredMethods())
        .stream()
        .filter(method0 -> Objects.equals(method0.getName(), lambda.getImplMethodName()))
        .findFirst()
        .orElseThrow(UnableToGuessMethodException::new);
return method.getParameters()[0].getName();

public void trackGC() throws InterruptedException {
    Object o = new Object();
    ReferenceQueue<Object> queue = new ReferenceQueue<>();
    PhantomReference<Object> phantomReference = new PhantomReference<>(o, queue);
    assertNull(queue.poll());
    o = null;
    System.gc();
    Thread.sleep(1000);
    assertNotNull(queue.poll());
}

PhantomReference<Object> phantomReference = new PhantomReference<>(o, queue);

new PhantomReference<>(o, queue);

PhantomReference<Object> phantomReference = new PhantomReference<>(o, queue);
phantomReference = null;