java学习笔记(4)

　　集合Collection的方法，java的ArrayList以及LinkedList都是继承自Collection，继承的结构：

运行下面代码

Collection<--List<--Vector 
Collection<--List<--ArrayList 
Collection<--List<--LinkedList 
Collection<--Set<--HashSet 
Collection<--Set<--HashSet<--LinkedHashSet 
Collection<--Set<--SortedSet<--TreeSet 
Map<--SortedMap<--TreeMap 
Map<--HashMap 

　　

　　Collection方法包括: removeAll(), retainAll(), containsAll() , toArray(), 前三个要传Collection作为参数;

运行下面代码

/*
    Map ==>> [ HashMap, TreeMap ]
    Collection ==>>  
         ==>> Set [HashSet, TreeSet]
         ==>> List [ArrayList, LinkedList]
*/
import java.util.*;

public class TestCollection {
    public static void  main(String[] args) {
        String apple = "apple";
        String banana = "banana";
        String pear = "pear";
        Collection<String> list = new ArrayList<String>();
        //Method add;
        list.add( apple );
        list.add( banana );
        list.add( pear );
        //use Interator;
        Iterator<String> it = list.iterator();
        while( it.hasNext() ) {
            String str = it.next();
            System.out.println( str );
        };
        /*
            method removeAll;
            @param Collection;
        */
        Collection<String> del = new ArrayList<String>();
        del.add(pear);
        list.removeAll( del );
        System.out.println( list );
        /*
            method retainAll;
            @param Collection;
        */
        del.remove(0);
        del.add( apple );
        list.retainAll( del );
        System.out.println( list );
        /*
            method containsAll;
            @param Collection;
        */
        list.add( pear );
        Boolean flag = list.containsAll( del );
        System.out.println( flag );
        /*
            method toArray;
        */
        //use Object[]; when i use String[] , it will not be ok;
        Object[] arr = list.toArray();
        for(int i=0; i<arr.length; i++) {
            System.out.println( arr[i] );
        }
    }
}

 

　　泛型的使用方法：

运行下面代码

//the T means is "String";
public class ArrayClass <T>{
    private T[] arr;
    public void setArr(T[] arr) {
        this.arr = arr;
    };
    public T[] getArr() {
        return arr;
    };

    public static void main(String[] args) {
        ArrayClass<String> arr = new ArrayClass<String>();
        String[] tempArr = {"0","1","2","3"};
        arr.setArr( tempArr );
        System.out.println( arr.getArr() );
        for( int i = 0; i < arr.getArr().length; i++ ) {
            System.out.println( arr.getArr()[i] );
        };
    }
}

 

　　

运行下面代码

public class OverClass<T>{
    private T over;
    public T getOver(){
        return over;
    };
    public void setOver(T over){
        this.over = over;
    };
    public static void main(String[] args) {
        OverClass<String> oc = new OverClass<String>();
        oc.setOver("hehe");
        System.out.println( oc.getOver() );

        OverClass<Boolean> ocb = new OverClass<Boolean>();
        ocb.setOver(false);
        System.out.println( ocb.getOver() );
    }
}

 

 

运行下面代码

public class MutiOverClass<T1,T2>{
    private T1[] arrString;
    private T2 bValue;
    public void setVal(T1[] arrs, T2 b) {
        this.arrString = arrs;
        this.bValue = b;
    };
    public String getVal() {
        return (arrString.toString()+bValue.toString());
    }
    public static void main(String[] args) {
        MutiOverClass<String, Boolean> muti = new MutiOverClass<String, Boolean>();
        String[] tempArr = {"0","1","2","3"};
        muti.setVal(tempArr,false);
        System.out.println( muti.getVal() );
    }
}

 

　　我们可以对泛型的数据进行预定义，使用extends，语法有点像继承啊， 我勒个去；

运行下面代码

import java.util.*;

public class LimitClass <T extends List>{
    private T t;
    //@Override
    public T get () {
        return  t;
    }
    public void set (T list) {
        this.t = list;
    }
    public static void main(String[] args) {
        LimitClass lc = new LimitClass<ArrayList>();
        System.out.println(lc.get());
        ArrayList<String> tempAL = new ArrayList<String>();
        tempAL.add("1");
        lc.set( tempAL );
        System.out.println(lc.get());
    }
}

 

　　HashMap的泛型使用方法， 实现首先要引入HashMap这个类，相当于JS中的闭包啊：

运行下面代码

import java.util.HashMap;
public class MutiHashMap <K,V>{
    public HashMap<K,V> map = new HashMap<K,V>();
    public void putMap  (K k, V v){
        map.put(k, v);
    };
    public V getVByK(K k) {
        return map.get(k);
    };
    public static void main(String[] args) {
        MutiHashMap muti = new MutiHashMap<Integer,String>();
        muti.map.put(1,"hehe");
        System.out.println( muti.map.get(1) );

        muti.putMap(4, "nono");
        System.out.println( muti.getVByK(4) );
    }
}

 

　　

　　枚举类型的使用，使用枚举的好处有：

　　1:枚举可以限定取值范围，所有的内容只能从指定范围中取得,

　　2:。。。。

　　3:。。。。

　　4:。。。。

运行下面代码

interface Constants{
    public static final int Constants_A = 1;
    public static final int Constants_B = 2;
}

public class ConstantsTest {
    //we can use enum to creates ..;
    enum Constants1 {
        Constants_A,
        Constants_B
    };

    public static void doit(int val){
        switch( val ) {
            case 1 :
                System.out.println("Constants_A ==>> val is" + val);
                break;
            case 2 :
                System.out.println("Constants_B ==>> val is" + val);
                break;
        };
    };
    public static void doit1(Constants1 c){

        switch( c ) {
            case Constants_A :
                System.out.println("Constants_A ==>> val is" + c);
                break;
            case Constants_B :
                System.out.println("Constants_B ==>> val is" + c);
                break;
        };

    };

    public static void main (String[] args) {
        ConstantsTest.doit(Constants.Constants_A);
        ConstantsTest.doit(Constants.Constants_B);
        ConstantsTest.doit1(Constants1.Constants_B);
        ConstantsTest.doit1(Constants1.Constants_B);
        System.out.println(Constants1.values()[0]);
        System.out.println(Constants1.values()[1]);
    };
}

 

　　enum枚举类型可以定义自己的方法和属性， enum相当于快速实例化构造函数， 直接访问对象的方法或者属性就可以了：

运行下面代码

public class CopyOfEnumIndexTest {
    //this is esay way to create instance, i guesss
    enum Contants2 {
        Contants_A("hehe"),
        Contants_B("oooo"),
        Contants_C("iiii"),
        Contants_D(4);
        private String description;
        private int i = 1;

        private Contants2 () {

        };
        private Contants2 (String description) {
            this.description = description;
        };
        private Contants2 ( int i ) {
            this.i += i;
        };
        private  int getI () {
            return this.i;
        };
        private String getDescription() {
            return this.description;
        };
    }

    public static void main(String[] args) {
        for(int i = 0; i< Contants2.values().length ; i++) {
            System.out.println( Contants2.values()[i].getI() );
            System.out.println( Contants2.values()[i].getDescription() );
        }
    }
}

 

　　　通过java的net获取当前电脑的ip和主机名：

运行下面代码

import java.net.*;
public class InetAddressDemo{
    public static void main(String[] args) {
        InetAddress intAddress;
        try{
            intAddress = InetAddress.getLocalHost();
            String localname = intAddress.getHostName();
            String localip = intAddress.getHostAddress();
            System.out.println("name is : " + localname + "; ip is :" + localip);
        }catch(UnknownHostException e) {
            e.printStackTrace();
        }
    }
}

 

 

　　服务器的SocketDemo和clientDemo， 服务器通过绑定本地的一个端口， 如果客户端连接这个端口， 服务端就返回信息， 客户端和服务端就可以进行交互

　　服务器的代码， 绑定本地的4331端口， 通过一个无限循环等待客户端发送消息， 等待客户端的连接：

运行下面代码

import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.net.ServerSocket;
import java.net.Socket;

public class ServerSocketDemo {
    public static void main(String[] args) {
        try{
            ServerSocket serverSocket = null;
            Socket clientSocket = null;
            String str = "";
            DataOutputStream out = null;
            DataInputStream in = null;

            serverSocket = new ServerSocket(4331);
            System.out.println("wating fro clients connect~");

            clientSocket = serverSocket.accept();
            in = new DataInputStream( clientSocket.getInputStream() );
            out = new DataOutputStream( clientSocket.getOutputStream() );

            while(true) {
                str = in.readUTF();
                out.writeUTF(str);
                System.out.println("get bytes : " + str);
                //Thread.sleep(1000);
            }
        }catch( IOException e ) {
            e.printStackTrace();
        }
    }
}

 

 　　客户端的代码：

运行下面代码

import java.io.DataOutputStream;
import java.io.DataInputStream;
import java.io.IOException;
import java.net.ServerSocket;
import java.net.Socket;

public class SocketDemo {
    public static void main(String[] args) {
        String str = null;
        Socket clientSocket;
        DataInputStream in = null;
        DataOutputStream out = null;

        try{
            clientSocket = new Socket("127.0.0.1",4331);
            in = new DataInputStream( clientSocket.getInputStream() );
            out = new DataOutputStream( clientSocket.getOutputStream() );
            out.writeUTF("I'm a client machine");
            int i = 0;
            while( true ) {
                out.writeUTF(i++ + "");
                str = in.readUTF();
                System.out.println("send data " + str);
                Thread.sleep(100);
            }
        }catch(Exception e) {
            e.printStackTrace();
        }
    }
}