BD1 - Java 2-1-2

2017-07-30 本文已影响11人 hongXkeX

We believe that writing is about content, about what you want to say – not about fancy formatting.
我们坚信写作写的是内容，所思所想，而不是花样格式。
— Ulysses for Mac

进程：

运行时（runtime）应用程序
进程之间的内存不是共享的（独占）
进程之间通信用socket套接字

多线程：

进程内并发执行的代码段
线程之间共享内存
主要创建灵活响应的桌面程序
每个运行着的线程对应一个stack
应用程序至少有一个线程——主线程
涉及并发就有多线程

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Thread.yield：

yield

（放弃cpu调用权，谦逊，瞬时动作）

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join

daemon 守护
Thread.setDaemon(true);

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线程间通信，共享资源问题

加锁—>由并行改为串行，防止并发访问
参照物，锁旗标
锁定权

对锁对象同步：

public class Ptest {
    public static void main(String[] args) {
        Salar s1 = new Salar("s1");
        Salar s2 = new Salar("s2");
        s1.start();
        s2.start();
        
    }
}

class Salar extends Thread{
    static int tickets = 100;
    // 锁对象（锁旗标）
    static Object lock = new Object();
    private String name;
    
    public Salar(String name){
        this.name = name;
    }
    
    public void run(){
        while(tickets>0){
            int temp = tickets;
            System.out.println(name+" : "+temp);
            tickets = tickets - 1;
        }
    }
    
    public int getTicket(){
        synchronized (lock) {
            int t = tickets;
            tickets = tickets - 1;
            return t;
        }
    }
}

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多线程加了同步会降低代码性能
同步代码块执行期间线程始终持有对象的监控权，其他线程处于阻塞状态

public class Ptest {
    public static void main(String[] args) {
        TicketPool pool = new TicketPool();
        Salar s1 = new Salar("s1",pool);
        Salar s2 = new Salar("s2",pool);
        Salar s3 = new Salar("s3",pool);
        Salar s4 = new Salar("s4",pool);
        
        s1.start();
        s2.start();
        s3.start();
        s4.start();
    }
}

class Salar extends Thread{
    private String name;
    private TicketPool pool;
    public Salar(String name, TicketPool pool){
        this.name = name;
        this.pool = pool;
    }
    public void run(){
        while(true){
            int no = pool.getTicket();
            if(no == 0){
                return;
            }else{
                System.out.println(name+" : "+no);
                Thread.yield();
            }
        }
    }
} 

// 票池
class TicketPool{
    private int tickets = 10;
    public int getTicket(){
        // 同步代码块  以票持本身作为锁旗标
        synchronized (this) {
            int temp = tickets;
            tickets = tickets - 1;
            return temp > 0 ? temp : 0;
        }
    }
}

同步方法是以当前所在对象做锁旗标：
synchronized(this) == 同步方法

synchronized 加在方法上：

public class Ptest {
    public static void main(String[] args) {
        TicketPool pool = new TicketPool();
        Salar s1 = new Salar("s1",pool);
        Salar s2 = new Salar("s2",pool);
        Salar s3 = new Salar("s3",pool);
        Salar s4 = new Salar("s4",pool);
        
        s1.start();
        s2.start();
        s3.start();
        s4.start();
    }
}

class Salar extends Thread{
    private String name;
    private TicketPool pool;
    public Salar(String name, TicketPool pool){
        this.name = name;
        this.pool = pool;
    }
    public void run(){
        while(true){
            int no = pool.getTicket();
            if(no == 0){
                return;
            }else{
                System.out.println(name+" : "+no);
                Thread.yield();
            }
        }
    }
} 

// 票池
class TicketPool{
    private int tickets = 10;
    public synchronized int getTicket(){
        int temp = tickets;
        tickets = tickets - 1;
        return temp > 0 ? temp : 0;
    }
}

用map存放身份证信息：

/**
         * List相当于人群，存储很多人（map）
         * 单个map信息的key必须不同 借助List使得可以存储多个map（人）的信息
         */
        List<HashMap<String, String>> list = new LinkedList<HashMap<String,String>>();
        
        /**
         * 每个map存一个人的信息
         */
        HashMap<String, String> map1 = new HashMap<String, String>();
        map1.put("name", "王二小");
        map1.put("sex", "男");
        map1.put("nation", "汉");
        map1.put("birth", "1990-09-12");
        map1.put("addr", "北京海淀区");
        map1.put("cardid", "123");
        list.add(map1);
        
        HashMap<String, String> map2 = new HashMap<String, String>();
        map2.put("name", "王二小");
        map2.put("sex", "男");
        map2.put("nation", "汉");
        map2.put("birth", "1990-09-12");
        map2.put("addr", "北京海淀区");
        map2.put("cardid", "123");
        list.add(map2);
        
        for(int i=0; i<list.size(); i++){
            System.out.println("第 "+i+" 个人信息：");
            System.out.println(list.get(i).get("name"));
            System.out.println(list.get(i).get("sex"));
            System.out.println(list.get(i).get("nation"));
            System.out.println(list.get(i).get("birth"));
            System.out.println(list.get(i).get("addr"));
            System.out.println(list.get(i).get("cardid"));
        }

// 输出：
第 0 个人信息：
王二小
男
汉
1990-09-12
北京海淀区
123
第 1 个人信息：
王二小
男
汉
1990-09-12
北京海淀区
123

基本数据类型	包装类
byte	Byte
short	Short
int	Integer
long	Long
float	Float
double	Double
boolean	Boolean
char	Character

世界上所有的追求都是因为热爱
一枚爱编码爱生活爱分享的IT信徒
— hongXkeX

BD1 - Java 2-1-2

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