Java多线程01_创建线程三种方式

灰太狼 2022-12-01 11:51 179阅读 0赞

**线程**

**程序**是指令、数据的有序集合，是静态的概念

**进程**是执行程序的一次执行过程，是动态概念

一个进程中可包含多个**线程**，java中有两个默认线程：**main线程** 和 **gc线程**

线程是CPU调度和执行的单位

--------------------

**线程创建1：继承Thread类（不推荐，避免OOP单继承局限性）**

创建线程：继承Thread类，重写run方法
        
    public class TestThread1 extends Thread{ 
    	
    	@Override
    	public void run() { 
    		for (int i = 0; i < 1000; i++) { 
    			System.out.println("线程1............");
    		}
    	}
        
    }
    
    
    运行线程：创建对象，调用start方法
        
    public class Test01 { 
    	
    	public static void main(String[] args) { 
    		
    		TestThread1 thread1 = new TestThread1();
    		thread1.start();
    		
    		for (int i = 0; i < 1000; i++) { 
    			System.out.println("main线程..........");
    		}
    	}
    	
    }

**示例：多线程下载网络图片**

依赖包：
    <dependency>
    	<groupId>commons-io</groupId>
    	<artifactId>commons-io</artifactId>
    	<version>2.6</version>
    </dependency>

public class TestThread2 extends Thread{ 
    	
    	private String url;
    	private String name;
    	
    	public TestThread2(String url, String name) { 
    		this.url=url;
    		this.name=name;
    	}
    	
    	@Override
    	public void run() { 
    		WebDownloader webDownloader = new WebDownloader();
    		webDownloader.downloader(url, name);
    		System.out.println("下载完成"+ name);
    	}
    	
    	public static void main(String[] args) { 
    		
    		String a = "https://timgsa.baidu.com/timg?image&quality=80&size=b9999_10000&sec=1598452051882&di=2c0925ea23483ac6c49affd40cbfb419&imgtype=0&src=http%3A%2F%2Fx0.ifengimg.com%2Fucms%2F2019_42%2FB575B6769D2A535CCB8186FB971B65DF853D14A0_w1620_h810.jpg";
    		TestThread2 t1 = new TestThread2(a,"1.jpg");
    		TestThread2 t2 = new TestThread2(a,"2.jpg");
    		TestThread2 t3 = new TestThread2(a,"3.jpg");
    		t1.start();
    		t2.start();
    		t3.start();
    		
    	}
    }
    
    class WebDownloader { 
    	
    	public void downloader(String url, String name) { 
    		try { 
    			FileUtils.copyURLToFile(new URL(url), new File(name));
    		} catch (IOException e) { 
    			System.out.println("IO异常，downloader方法出现问题");
    			e.printStackTrace();
    		}
    	}
    	
    }

**线程创建2：实现Runnable接口（推荐，避免单继承局限性，灵活，方便同一对象被多个线程使用）**

创建线程：实现Runnable接口，实现run方法
    开启线程：创建自定义的线程对象和Thread类对象，将自定义的线程对象传入Thread类构造，调用start方法
    源码：Thread类实现了Runnable接口
    
    public class TestThread3 implements Runnable{ 
    
    	@Override
    	public void run() { 
    		for (int i = 0; i < 1000; i++) { 
    			System.out.println("实现Runnable接口的线程......");
    		}
    	}
    
    	public static void main(String[] args) { 
    		TestThread3 testThread3 = new TestThread3();
    		new Thread(testThread3).start();
    		
    		for (int i = 0; i < 1000; i++) { 
    			System.out.println("main线程.............");
    		}
    		
    	}
    }

**示例修改：多线程下载网络图片**

public class TestThread2 implements Runnable{ 
    	
    	private String url;
    	private String name;
    	
    	public TestThread2(String url, String name) { 
    		this.url=url;
    		this.name=name;
    	}
    	
    	@Override
    	public void run() { 
    		WebDownloader webDownloader = new WebDownloader();
    		webDownloader.downloader(url, name);
    		System.out.println("下载完成"+ name);
    	}
    	
    	public static void main(String[] args) { 
    		
    		String a = "https://timgsa.baidu.com/timg?image&quality=80&size=b9999_10000&sec=1598452051882&di=2c0925ea23483ac6c49affd40cbfb419&imgtype=0&src=http%3A%2F%2Fx0.ifengimg.com%2Fucms%2F2019_42%2FB575B6769D2A535CCB8186FB971B65DF853D14A0_w1620_h810.jpg";
    		TestThread2 t1 = new TestThread2(a,"1.jpg");
    		TestThread2 t2 = new TestThread2(a,"2.jpg");
    		TestThread2 t3 = new TestThread2(a,"3.jpg");
    		new Thread(t1).start;
    		new Thread(t2).start;
    		new Thread(t3).start;
    		
    	}
    }
    
    class WebDownloader { 
    	
    	public void downloader(String url, String name) { 
    		try { 
    			FileUtils.copyURLToFile(new URL(url), new File(name));
    		} catch (IOException e) { 
    			System.out.println("IO异常，downloader方法出现问题");
    			e.printStackTrace();
    		}
    	}
    	
    }

**多个线程同时操作同一个对象示例：抢票**  
问题：多个线程同时操作同一资源时，线程不安全，出现数据紊乱现象

public class TestThread4 implements Runnable{ 
    	
    	private int ticketNums = 10;
    
    	@Override
    	public void run() { 
    		while(true) { 
    			if(ticketNums<=0) { 
    				break;
    			}
    			try { 
    				Thread.sleep(100);
    			} catch (InterruptedException e) { 
    				// TODO Auto-generated catch block
    				e.printStackTrace();
    			}
    			int num = 11-ticketNums;
    			System.out.println(Thread.currentThread().getName()+"拿到了第"+num+"张票");
    			ticketNums--;
    		}
    	}
    
    	public static void main(String[] args) { 
    		TestThread4 testThread4 = new TestThread4();
    		new Thread(testThread4,"张三").start();
    		new Thread(testThread4,"李四").start();
    		new Thread(testThread4,"王五").start();
    	}
    }

李四拿到了第1张票
    王五拿到了第1张票
    张三拿到了第1张票
    张三拿到了第4张票
    王五拿到了第4张票
    李四拿到了第4张票
    王五拿到了第7张票
    张三拿到了第7张票
    李四拿到了第7张票
    张三拿到了第10张票
    王五拿到了第10张票
    李四拿到了第10张票

**线程创建3：实现Callable接口（了解即可）**

创建线程：实现Callable接口，实现call()方法
    运行线程：创建线程池，提交执行线程对象，获取结果，关闭线程池
    
    public class TestThread5 implements Callable<Boolean>{ 
    	
    	private String url;
    	private String name;
    	
    	public TestThread5(String url, String name) { 
    		this.url=url;
    		this.name=name;
    	}
    
    	@Override
    	public Boolean call() throws Exception { 
    		WebDownloader webDownloader = new WebDownloader();
    		webDownloader .downloader(url, name);
    		System.out.println("下载完成"+ name);
    		return true;
    	}
    	
    	public static void main(String[] args) throws InterruptedException, ExecutionException { 
    		String a = "https://timgsa.baidu.com/timg?image&quality=80&size=b9999_10000&sec=1598452051882&di=2c0925ea23483ac6c49affd40cbfb419&imgtype=0&src=http%3A%2F%2Fx0.ifengimg.com%2Fucms%2F2019_42%2FB575B6769D2A535CCB8186FB971B65DF853D14A0_w1620_h810.jpg";
    		TestThread5 t1 = new TestThread5(a,"1.jpg");
    		TestThread5 t2 = new TestThread5(a,"2.jpg");
    		TestThread5 t3 = new TestThread5(a,"3.jpg");
    		//创建执行服务
    		ExecutorService threadPool = Executors.newFixedThreadPool(3);
    		//提交执行
    		Future<Boolean> result1 = threadPool.submit(t1);
    		Future<Boolean> result2 = threadPool.submit(t2);
    		Future<Boolean> result3 = threadPool.submit(t3);
    		//获取结果
    		Boolean r1 = result1.get();
    		Boolean r2 = result2.get();
    		Boolean r3 = result3.get();
    		System.out.println(r1);
    		System.out.println(r2);
    		System.out.println(r3);
    		//关闭服务
    		threadPool.shutdownNow();
    		
    	}
    	
    }
    
    class WebDownloader { 
    	
    	public void downloader(String url, String name) { 
    		try { 
    			FileUtils.copyURLToFile(new URL(url), new File(name));
    		} catch (IOException e) { 
    			System.out.println("IO异常，downloader方法出现问题");
    			e.printStackTrace();
    		}
    	}
    	
    }

**Lambda表达式**

**避免匿名内部类定义过多**  
**让代码更简洁**

**函数式接口**：只包含唯一一个抽象方法的接口叫函数式接口

public interface Runnable{ 
    	public abstract void run();
    }

传统方式：

public class TestLambda { 
    	public static void main(String[] args) { 
    		ILike like = new Like();
    		like.lambda();
    	}
    }
    
    //定义一个函数式接口
    interface ILike{ 
    	void lambda();
    }
    
    //实现类
    class Like implements ILike{ 
    
    	@Override
    	public void lambda() { 
    		System.out.println("I like lambda");
    	}
    	
    }

使用Lambda表达式：

public class TestLambda { 
    	public static void main(String[] args) { 
    		ILike like = ()->{ 
    			System.out.println("I like lambda2");
    		};
    		like.lambda();
    	}
    }
    
    //定义一个函数式接口
    interface ILike{ 
    	void lambda();
    }