Parent interface of Collection: Iterable Interface
A class that implements the Iterable can be used with the new for-loop.
The Iterable interface has only one method:
public interface Iterable<T> {
public Iterator<T> iterator();
}
It is possible to use your own collection type classes with the new for-loop. To do so, your class must implement thejava.lang.Iterable<E> interface. Here is a very basic example:
public class MyCollection<E> implements Iterable<E>{
public Iterator<E> iterator() {
return new MyIterator<E>();
}
}
And here is the corresponding implementation skeleton of the MyIterator class:
public class MyIterator <T> implements Iterator<T> {
public boolean hasNext() {
//implement...
}
public T next() {
//implement...;
}
public void remove() {
//implement... if supported.
}
}
迭代器应用： list l = new ArrayList(); l.add("aa"); l.add("bb"); l.add("cc"); for (Iterator iter = l.iterator(); iter.hasNext();) { String str = (String)iter.next(); System.out.println(str); }
Java sockets
A socket is one end-point of a two-way communication link between two programs running on the network. Socket classes are used to represent the connection between a client program and a server program. The java.net package provides two classes--Socket and ServerSocket--that implement the client side of the connection and the server side of the connection, respectively.
总： Client[port] <----->Server[listening port, communication port] ，
Server side: ServerSocket serverSocket = new ServerSocket(5000); //Server will be listening to requests from clients on port 5000
Client side: Socket chatSocket = new Socket("192.1.168.100", 5000); //The server is running on port 5000 at 192.1.168.100
Socket sock = serverSocket.accept(); //Server will return a new port to communicate with clients
InputStreamReader reader = new InputStreamReader(chatSocket.getInputStream());
BufferedReader breader = new BufferedReader(reader);
String msg = breader.readLine();
Reflection
1, Get Class: 如果compile time已知class，那可以A.class。如果runtime才知class name，那可以Class.forName("className");
Get Class以后就可以获取这个Class的所有信息，例如.getMethods(), .getConstructors(), .getInterfaces(), .getFields(), .getAnnotations()...
2, Get constructor以后可以Instantiate object：
Constructor constructor=A.class.getConstructor(String.class);
A a= (A) constructor.newInstance("StringArgument");
3, Get fields以后可以get 或set object里的这个field:
Field someField = A.class.getField("FieldName"); //.getField()方法只能获取public fields
A a = new A();
Object value = someField.get(a);
someField.set(a, value);
4,Get method以后可以invoke这个method on some object:
Method method = A.class.getMethod("MethodName", String.class); //.getMethod()方法只能获取public methods
Object returnValue = method.invoke(new A(), "StringArgument");
5, Get private field/method
Field privateField = A.class.getDeclaredField("FieldName"); //or .getDeclaredMethod("MethodName");
privateField.setAccessible(true);
Object fieldValue = privateField.get(new A());
6, Get annotations
Annotations可以是在class上，或者method, field, parameter上...
在定义自己的@interface的时候，如果@Retention(RetentionPolicy.RUNTIME)表示在runtime时可以获取这个annotation.
Annotation annotation = A.class.getAnnotation(MyAnnotation.class);
if(annotation instanceof MyAnnotation) {annotation.getName();...}
Proxy
To create dynamic implementations of interface at runtime with the help of reflection.
InvocationHandler handler = new MyInvocationHandler(); //implement .invoke()方法
MyInterface proxy = (MyInterface) Proxy.newProxyInstance(MyInterface.class.getClassLoader(), new Class[] {MyInterface.class}, handler);
asd