线程(第三天)

声明:由于学习所用环境为JDK1.8,所有java代码均在JDK1.8中测试通过,如果环境发生改变,可能会有错误发生!

一、通过Callable接口实现多线程

1.  Callable接口介绍
     java.util.concurrent.Callable是一个泛型接口,只有一个call()方法
     call()方法抛出Exception异常,且返回一个指定的泛型类的对象
2. Callable接口实现线程的应用场景
     当父线程想要获取子线程的运行结果时。
3. 使用Callable接口实现多线程的步骤
    第一步:创建Callable子类的实例化对象。
   第二步:创建FutureTask 对象,并将Callable对象传入FutureTask的构造方法中(注意:FutureTask实现了Runnable接口和Future接口)
   第三步:实例化Thread对象,并在构造方法中传入FutureTask对象
   第四步:启动线程  

package callable;

import java.util.concurrent.FutureTask;

public class CallableDemo {

	public static void main(String[] args) {
		GeneralCallable call=new GeneralCallable();   // 创建Callable子类的实例化对象  
		FutureTask<String> task=new FutureTask<String>(call);   // 创建FutureTask 对象,
                                                                           并将Callable对象传入FutureTask的构造方法中
		Thread t=new Thread(task,"魏延线程");  // 实例化Thread对象,并在构造方法中传入FutureTask对象 
		t.start();   // 启动线程
		System.out.println(Thread.currentThread().getName()+"进入休眠状态(休眠5秒)...");
		try {
			Thread.sleep(5000);
			String report=task.get();   // 获取子线程的返回值
			System.out.println("子线程的返回结果是:"+report);
		} catch (Exception e) {
			e.printStackTrace();
		}
	}
}

二、生产者-消费者问题

生产者线程不断生产,消费者线程不断取走生产者生产的产品。
   Object中的几个方法支持:
   wait()   线程等待,当前线程进入调用对象的线程等待池
   notify()  唤醒1个等待线程
   notifyAll() 唤醒全部等待的线程
注意:以上三个方法都必须在同步机制(同步方法和同步代码)中调用

1、“一对多”

package onetoonepc;

public class Breakfast {
	private String food;
	private String drink;
	private boolean flag=false;

	public Breakfast() {

	}

	public Breakfast(String food, String drink) {
		super();
		this.food = food;
		this.drink = drink;
	}

	public synchronized void makeBreakfast(String food, String drink) {
		if(flag){
			try {
				wait();
			} catch (InterruptedException e) {
				e.printStackTrace();
			}
		}
		this.food = food;
		try {
			Thread.sleep(1000);
		} catch (InterruptedException e) {
			e.printStackTrace();
		}
		this.drink = drink;
		flag=true;
		notify();
	}

	public synchronized void haveBreakfast() {
		if(!flag){
			try {
				wait();
			} catch (InterruptedException e) {
				e.printStackTrace();
			}
		}
		try {
			Thread.sleep(1000);
		} catch (InterruptedException e) {
			e.printStackTrace();
		}
		System.out.println(food + "=====》" + drink);
		flag=false;
		notify();
	}
}
package onetoonepc;

public class Producer implements Runnable{
	private Breakfast bf;
	public Producer(Breakfast bf){
		this.bf=bf;
	}
	
	@Override
	public void run() {
		for (int i = 1; i <= 7; i++) {
			if(i%2==0){
				this.bf.makeBreakfast("馒头", "稀饭");
			}else {
				this.bf.makeBreakfast("bread", "milk");
			}
		}
	}

}
package onetoonepc;

public class Consumer implements Runnable {
	private Breakfast bf;
	public Consumer(Breakfast bf){
		this.bf=bf;
	}
	@Override
	public void run() {
		for (int i = 1; i <=7; i++) {
			this.bf.haveBreakfast();
		}
	}
}
package onetoonepc;

public class Test {

	public static void main(String[] args) {
		Breakfast bf=new Breakfast();
		new Thread(new Producer(bf)).start();
		new Thread(new Consumer(bf)).start();
	}
}
2、“多对多”
package many2many;

public class Product {
	private int count=0;
	private final int MAX=5;
	
	public synchronized void makeProduct(){
		String threadName=Thread.currentThread().getName();
		if(count>=MAX){
			System.out.println(threadName+"货物已满");
			try {
				notifyAll();
				wait();
			} catch (InterruptedException e) {
				e.printStackTrace();
			}
		}else{
			try {
				Thread.sleep(1000);
			} catch (InterruptedException e) {
				e.printStackTrace();
			}
			count++;
			System.out.println(threadName+"生产了一件商品,当前商品数量是"+count);
			notifyAll();
		}
	}
	
	public synchronized void sellProduct(){
		String threadName=Thread.currentThread().getName();
		if(count<=0){
			System.out.println(threadName+"商品暂无库存,请等待");
			try {
				notifyAll();
				wait();
			} catch (InterruptedException e) {
				e.printStackTrace();
			}
		}else{
			try {
				Thread.sleep(1000);
			} catch (InterruptedException e) {
				e.printStackTrace();
			}
			count--;
			System.out.println(threadName+"消费了一件商品,剩余商品数量为"+count);
		}
	}
}
package many2many;

public class Producer implements Runnable {
	private Product pro = new Product();

	public Producer(Product pro) {
		this.pro = pro;
	}

	@Override
	public void run() {
		while(true){
		pro.makeProduct();
		}
	}
}
package many2many;

public class Consumer implements Runnable {
	private Product pro;

	public Consumer(Product pro) {
		this.pro = pro;
	}

	@Override
	public void run() {
		while(true){
		pro.sellProduct();
		}
	}
}
package many2many;

public class Test {

	public static void main(String[] args) {
		Product product=new Product();
		new Thread(new Producer(product),"生产者1").start();
		new Thread(new Producer(product),"生产者1").start();
		new Thread(new Consumer(product),"消费者1").start();
		new Thread(new Consumer(product),"消费者1").start();
	}

}
三、多线程下载(复制)文件
使用RandomAccessFile与InputStream的skip(long n)方法使每个线程负责文件的每一部分读写

package download;

import java.io.*;

public class DownRunnable implements Runnable{
	private File srcFile;
	private long partTask;
	private long startPos;
	private RandomAccessFile raf;
	public  DownRunnable(File srcFile,long partTask,long startPos,RandomAccessFile raf){
		this.srcFile=srcFile;
		this.partTask=partTask;
		this.startPos=startPos;
		this.raf=raf;
	}

	@Override
	public void run() {
		System.out.println(Thread.currentThread().getName()+"从"+startPos+"个字节开始读");
		InputStream input=null;
		try {
			input=new FileInputStream(srcFile);
			byte[] b=new byte[1024*1024*10];
			int len=0;
			int count=0;
			while((len=input.read(b))!=-1 && count<partTask){
				raf.write(b,0,len);
				count+=len;
				System.out.println(Thread.currentThread().getName()+"已经写了"+count+"个字节");
			}
		} catch (Exception e) {
			e.printStackTrace();
		}
	}
}
package download;

import java.io.File;
import java.io.RandomAccessFile;

public class Client {

	public static void main(String[] args) throws Exception{
		File srcFile=new File("D:"+File.separator+"Qiyi"+File.separator+"Offline"+File.separator+"123.qsv");
		long partTask=srcFile.length()/8;
		RandomAccessFile raf=null;
		raf=new RandomAccessFile("e:"+File.separator+srcFile.getName(),"rw");
		for (int i = 0; i <8; i++) {
			long startPos=i*partTask;
			DownRunnable dr=new DownRunnable(srcFile, partTask, startPos, raf);
			new Thread(dr,i+"线程").start();
		}
	}
}
一般情况下,会将耗时操作放入线程中。

评论
添加红包

请填写红包祝福语或标题

红包个数最小为10个

红包金额最低5元

当前余额3.43前往充值 >
需支付:10.00
成就一亿技术人!
领取后你会自动成为博主和红包主的粉丝 规则
hope_wisdom
发出的红包
实付
使用余额支付
点击重新获取
扫码支付
钱包余额 0

抵扣说明:

1.余额是钱包充值的虚拟货币,按照1:1的比例进行支付金额的抵扣。
2.余额无法直接购买下载,可以购买VIP、付费专栏及课程。

余额充值