Java并发编程-01-线程的创建和线程信息获取

一、创建线程的方式

1、继承Thread类，覆盖run方法

2、实现Runnable接口，创建Thread类的实例，通过构造方法实现

3、Runnable接口只有一个抽象的run方法，也就是说Runnable接口本身不支持多线程

public interface Runnable {
/**
* When an object implementing interface <code>Runnable</code> is used
* to create a thread, starting the thread causes the object's
* <code>run</code> method to be called in that separately executing
* thread.
* <p>
* The general contract of the method <code>run</code> is that it may
* take any action whatsoever.
*
* @see java.lang.Thread#run()
*/
public abstract void run();
}

4、Runnable接口多线程的实现
查看Thread类的源代码，可以看到很多构造函数的参数是Runnable类或者Runnable的子类，即通过Thread类的构造方法类启动Runnable接口实现多线程

/**
* Allocates a new {@code Thread} object. This constructor has the same
* effect as {@linkplain #Thread(ThreadGroup,Runnable,String) Thread}
* {@code (null, target, gname)}, where {@code gname} is a newly generated
* name. Automatically generated names are of the form
* {@code "Thread-"+}<i>n</i>, where <i>n</i> is an integer.
*
* @param target
* the object whose {@code run} method is invoked when this thread
* is started. If {@code null}, this classes {@code run} method does
* nothing.
*/
public Thread(Runnable target) {
init(null, target, "Thread-" + nextThreadNum(), 0);
}



5、Runnable接口的优势

避免单继承的局限，一个类可以继承多个接口。
适合于资源的共享
6、Thread类是Runnable接口的一个实现子类



二、线程信息的获取

id:保存了线程的唯一标识符 Name：线程名称

Priority：保存了线程的优先级，线程的优先级是从一到10,1是最低优先级，10是最高优先级。

status：线程的状态，java中线程有6个状态：new，runnable，blocked，waiting，time,waiting，terminated

测试代码：

线程类

package com.concurrent.threadManager;

/**
* 线程的创建和运行
*
* @author Nicholas
*
*/

public class Calculator implements Runnable {

private int number;

public Calculator(int number) {
this.number = number;
}

@Override
public void run() {
for (int i = 0; i <= 10; i++) {
System.out.printf("%s : %d * %d = %d\n", Thread.currentThread()
.getName(), number, i, i * number);
}
}
}


主方法：
package com.concurrent.threadManager;

import java.io.FileWriter;
import java.io.IOException;
import java.io.PrintWriter;
import java.lang.Thread.State;

public class MainTest {

/**
* 对于实现了runnable接口的类来说，创建一个Thread对象并不会创建一个新的执行线程 同样的，调用他的run方法，也不会创建一个新的执行线程
* 只有调用他的start方法事，才会创建一个新的执行线程
*
* @param args
*/

public void testCreateThread() {
for (int j = 0; j <= 10; j++) {
Calculator calculator = new Calculator(j);
Thread thread = new Thread(calculator);
thread.start();
}
}

/**
* id:保存了线程的唯一标识符 Name：线程名称
* Priority：保存了线程的优先级，线程的优先级是从一到10,1是最低优先级，10是最高优先级。
* status：线程的状态，java中线程有6个状态：new，runnable，blocked，waiting，time
* waiting，terminated
*/
public static void WriteThreadInfo(PrintWriter printWriter, Thread thread,
State state) {
printWriter.printf("Main : ID %d - %s\n", thread.getId(),
thread.getName());
printWriter.printf("Main : Priority: %d\n", thread.getPriority());
printWriter.printf("Main : Old status -%s\n", state);
printWriter.printf("Main : New status -%s\n", thread.getState());
printWriter.printf("Main : *******************************\n");
}

public static void main(String[] args) {
Thread threads[] = new Thread[10];// 创建10个线程
Thread.State status[] = new Thread.State[10];// 创建保存10个线程状态的数组

// 创建10个Calculator对象数组，为每个对象都设置不同的数字，然后用他们作为thread构造器的参数，创建10个线程对象
// 将偶数部分优先级设为最高，奇数的设置为最低
for (int i = 0; i < 10; i++) {
threads[i] = new Thread(new Calculator(i));
if (i % 2 == 0) {
threads[i].setName("高优先级 ---Thread -" + i);
threads[i].setPriority(Thread.MAX_PRIORITY);
} else {
threads[i].setName("低优先级 ---Thread -" + i);
threads[i].setPriority(Thread.MIN_PRIORITY);
}
}

// 创建PrintWriter对象，把线程的演变保存到log文本中
// 把10个线程的状态写入文件，现在线程的状态是NEW
try (FileWriter fileWriter = new FileWriter(".\\log.txt");
PrintWriter printWriter = new PrintWriter(fileWriter);) {
for (int i = 0; i < 10; i++) {
printWriter.println("Main:Status of Thread " + i + " : "
+ threads[i].getState());
status[i] = threads[i].getState();
}
// 线程执行
for (int i = 0; i < 10; i++) {
threads[i].start();
}

// 把状态发生了变化的，写入到文件
boolean finished = false;
while (!finished) {
for (int i = 0; i < 10; i++) {
if (threads[i].getState() != status[i]) {
WriteThreadInfo(printWriter, threads[i], status[i]);
status[i] = threads[i].getState();
}
}
finished = true;
for (int i = 0; i < 10; i++) {
finished = finished
&& (threads[i].getState() == State.TERMINATED);
}
}
} catch (IOException e) {
e.printStackTrace();
}
}
}


打印的log信息
Main:Status of Thread 0 : NEW
Main:Status of Thread 1 : NEW
Main:Status of Thread 2 : NEW
Main:Status of Thread 3 : NEW
Main:Status of Thread 4 : NEW
Main:Status of Thread 5 : NEW
Main:Status of Thread 6 : NEW
Main:Status of Thread 7 : NEW
Main:Status of Thread 8 : NEW
Main:Status of Thread 9 : NEW
Main : ID 10 - 高优先级 ---Thread -0
Main : Priority: 10
Main : Old status -NEW
Main : New status -RUNNABLE
Main : *******************************
Main : ID 11 - 低优先级 ---Thread -1
Main : Priority: 1
Main : Old status -NEW
Main : New status -BLOCKED
Main : *******************************
Main : ID 12 - 高优先级 ---Thread -2
Main : Priority: 10
Main : Old status -NEW
Main : New status -BLOCKED
Main : *******************************
Main : ID 13 - 低优先级 ---Thread -3
Main : Priority: 1
Main : Old status -NEW
Main : New status -BLOCKED
Main : *******************************
Main : ID 14 - 高优先级 ---Thread -4
Main : Priority: 10
Main : Old status -NEW
Main : New status -BLOCKED
Main : *******************************
Main : ID 15 - 低优先级 ---Thread -5
Main : Priority: 1
Main : Old status -NEW
Main : New status -BLOCKED
Main : *******************************
Main : ID 16 - 高优先级 ---Thread -6
Main : Priority: 10
Main : Old status -NEW
Main : New status -BLOCKED
Main : *******************************
Main : ID 17 - 低优先级 ---Thread -7
Main : Priority: 1
Main : Old status -NEW
Main : New status -BLOCKED
Main : *******************************
Main : ID 18 - 高优先级 ---Thread -8
Main : Priority: 10
Main : Old status -NEW
Main : New status -BLOCKED
Main : *******************************
Main : ID 19 - 低优先级 ---Thread -9
Main : Priority: 1
Main : Old status -NEW
Main : New status -BLOCKED
Main : *******************************
Main : ID 10 - 高优先级 ---Thread -0
Main : Priority: 10
Main : Old status -RUNNABLE
Main : New status -TERMINATED
Main : *******************************
Main : ID 15 - 低优先级 ---Thread -5
Main : Priority: 1
Main : Old status -BLOCKED
Main : New status -RUNNABLE
Main : *******************************
Main : ID 17 - 低优先级 ---Thread -7
Main : Priority: 1
Main : Old status -BLOCKED
Main : New status -RUNNABLE
Main : *******************************
Main : ID 15 - 低优先级 ---Thread -5
Main : Priority: 1
Main : Old status -RUNNABLE
Main : New status -TERMINATED
Main : *******************************
Main : ID 17 - 低优先级 ---Thread -7
Main : Priority: 1
Main : Old status -RUNNABLE
Main : New status -TERMINATED
Main : *******************************
Main : ID 19 - 低优先级 ---Thread -9
Main : Priority: 1
Main : Old status -BLOCKED
Main : New status -RUNNABLE
Main : *******************************
Main : ID 19 - 低优先级 ---Thread -9
Main : Priority: 1
Main : Old status -RUNNABLE
Main : New status -TERMINATED
Main : *******************************
Main : ID 13 - 低优先级 ---Thread -3
Main : Priority: 1
Main : Old status -BLOCKED
Main : New status -RUNNABLE
Main : *******************************
Main : ID 13 - 低优先级 ---Thread -3
Main : Priority: 1
Main : Old status -RUNNABLE
Main : New status -TERMINATED
Main : *******************************
Main : ID 11 - 低优先级 ---Thread -1
Main : Priority: 1
Main : Old status -BLOCKED
Main : New status -RUNNABLE
Main : *******************************
Main : ID 18 - 高优先级 ---Thread -8
Main : Priority: 10
Main : Old status -BLOCKED
Main : New status -BLOCKED
Main : *******************************
Main : ID 14 - 高优先级 ---Thread -4
Main : Priority: 10
Main : Old status -BLOCKED
Main : New status -BLOCKED
Main : *******************************
Main : ID 12 - 高优先级 ---Thread -2
Main : Priority: 10
Main : Old status -BLOCKED
Main : New status -BLOCKED
Main : *******************************
Main : ID 14 - 高优先级 ---Thread -4
Main : Priority: 10
Main : Old status -RUNNABLE
Main : New status -BLOCKED
Main : *******************************
Main : ID 18 - 高优先级 ---Thread -8
Main : Priority: 10
Main : Old status -BLOCKED
Main : New status -BLOCKED
Main : *******************************
Main : ID 11 - 低优先级 ---Thread -1
Main : Priority: 1
Main : Old status -RUNNABLE
Main : New status -BLOCKED
Main : *******************************
Main : ID 16 - 高优先级 ---Thread -6
Main : Priority: 10
Main : Old status -BLOCKED
Main : New status -TERMINATED
Main : *******************************
Main : ID 11 - 低优先级 ---Thread -1
Main : Priority: 1
Main : Old status -BLOCKED
Main : New status -RUNNABLE
Main : *******************************
Main : ID 14 - 高优先级 ---Thread -4
Main : Priority: 10
Main : Old status -BLOCKED
Main : New status -TERMINATED
Main : *******************************
Main : ID 18 - 高优先级 ---Thread -8
Main : Priority: 10
Main : Old status -BLOCKED
Main : New status -TERMINATED
Main : *******************************
Main : ID 12 - 高优先级 ---Thread -2
Main : Priority: 10
Main : Old status -BLOCKED
Main : New status -TERMINATED
Main : *******************************


可以看出
1、高优先级的线程比低有限级的线程结束的早

2、jvm使用线程的Priority属性来决定某一刻由那个线程来使用CPU。

3、如果setPriority设置的优先级不是1到10，就会抛出IllegalArgumentException异常