以前沒有寫筆記的習(xí)慣，現(xiàn)在慢慢的發(fā)現(xiàn)及時(shí)總結(jié)是多么的重要了，呵呵。雖然才大二，但是也快要畢業(yè)了，要加油了。
這一篇文章主要關(guān)于java多線程，主要還是以例子來(lái)驅(qū)動(dòng)的。因?yàn)橹v解多線程的書籍和文章已經(jīng)很多了，所以我也不好意思多說(shuō)，呵呵、大家可以去參考一些那些書籍。我這個(gè)文章主要關(guān)于實(shí)際的一些問(wèn)題。同時(shí)也算是我以后復(fù)習(xí)的資料吧，。呵呵大家多多指教。
同時(shí)希望多結(jié)交一些技術(shù)上的朋友。謝謝。
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java中的多線程
在java中要想實(shí)現(xiàn)多線程，有兩種手段，一種是繼續(xù)Thread類，另外一種是實(shí)現(xiàn)Runable接口。
對(duì)于直接繼承Thread的類來(lái)說(shuō)，代碼大致框架是：
}
public hello() {
}
public hello(String name) {
this.name = name;
}
public void run() {
for (int i = 0; i < 5; i++) {
System.out.println(name + "運(yùn)行 " + i);
}
}
public static void main(String[] args) {
hello h1=new hello("A");
hello h2=new hello("B");
h1.run();
h2.run();
}
private String name;
}
}
public hello() {
}
public hello(String name) {
this.name = name;
}
public void run() {
for (int i = 0; i < 5; i++) {
System.out.println(name + "運(yùn)行 " + i);
}
}
public static void main(String[] args) {
hello h1=new hello("線程A");
Thread demo= new Thread(h1);
hello h2=new hello("線程Ｂ");
Thread demo1=new Thread(h2);
demo.start();
demo1.start();
}
private String name;
}
關(guān)于選擇繼承Thread還是實(shí)現(xiàn)Runnable接口？
其實(shí)Thread也是實(shí)現(xiàn)Runnable接口的：
public static void main(String[] args) {
hello h1 = new hello();
hello h2 = new hello();
hello h3 = new hello();
h1.start();
h2.start();
h3.start();
}
private int count = 5;
}
public static void main(String[] args) {
hello he=new hello();
new Thread(he).start();
}
private int count = 5;
}
總結(jié)一下吧：
實(shí)現(xiàn)Runnable接口比繼承Thread類所具有的優(yōu)勢(shì)：
1）：適合多個(gè)相同的程序代碼的線程去處理同一個(gè)資源
2）：可以避免java中的單繼承的限制
3）：增加程序的健壯性，代碼可以被多個(gè)線程共享，代碼和數(shù)據(jù)獨(dú)立。
所以，本人建議大家勁量實(shí)現(xiàn)接口。
public static void main(String[] args) {
hello he = new hello();
new Thread(he,"A").start();
new Thread(he,"B").start();
new Thread(he).start();
}
}
在java中，每次程序運(yùn)行至少啟動(dòng)2個(gè)線程。一個(gè)是main線程，一個(gè)是垃圾收集線程。因?yàn)槊慨?dāng)使用java命令執(zhí)行一個(gè)類的時(shí)候，實(shí)際上都會(huì)啟動(dòng)一個(gè)ＪＶＭ，每一個(gè)ｊＶＭ實(shí)習(xí)在就是在操作系統(tǒng)中啟動(dòng)了一個(gè)進(jìn)程。
判斷線程是否啟動(dòng)
public static void main(String[] args) {
hello he = new hello();
Thread demo = new Thread(he);
System.out.println("線程啟動(dòng)之前---》" + demo.isAlive());
demo.start();
System.out.println("線程啟動(dòng)之后---》" + demo.isAlive());
}
}
線程的強(qiáng)制執(zhí)行：
public static void main(String[] args) {
hello he = new hello();
Thread demo = new Thread(he,"線程");
demo.start();
for(int i=0;i<50;++i){
if(i>10){
try{
demo.join(); //強(qiáng)制執(zhí)行demo
}catch (Exception e) {
e.printStackTrace();
}
}
System.out.println("main 線程執(zhí)行-->"+i);
}
}
}
線程的休眠：
public static void main(String[] args) {
hello he = new hello();
Thread demo = new Thread(he, "線程");
demo.start();
}
}
線程的中斷：
public static void main(String[] args) {
hello he = new hello();
Thread demo = new Thread(he, "線程");
demo.start();
try{
Thread.sleep(2000);
}catch (Exception e) {
e.printStackTrace();
}
demo.interrupt(); //2s后中斷線程
}
}
在java程序中，只要前臺(tái)有一個(gè)線程在運(yùn)行，整個(gè)java程序進(jìn)程不會(huì)小時(shí)，所以此時(shí)可以設(shè)置一個(gè)后臺(tái)線程，這樣即使java進(jìn)程小時(shí)了，此后臺(tái)線程依然能夠繼續(xù)運(yùn)行。
public static void main(String[] args) {
hello he = new hello();
Thread demo = new Thread(he, "線程");
demo.setDaemon(true);
demo.start();
}
}
public static void main(String[] args) {
Thread h1=new Thread(new hello(),"A");
Thread h2=new Thread(new hello(),"B");
Thread h3=new Thread(new hello(),"C");
h1.setPriority(8);
h2.setPriority(2);
h3.setPriority(6);
h1.start();
h2.start();
h3.start();
}
}
另外，主線程的優(yōu)先級(jí)是5.
線程的禮讓。
在線程操作中，也可以使用yield（）方法，將一個(gè)線程的操作暫時(shí)交給其他線程執(zhí)行。
public static void main(String[] args) {
Thread h1=new Thread(new hello(),"A");
Thread h2=new Thread(new hello(),"B");
h1.start();
h2.start();
}
}
同步和死鎖：
【問(wèn)題引出】:比如說(shuō)對(duì)于買票系統(tǒng)，有下面的代碼：
public static void main(String[] args) {
hello he=new hello();
Thread h1=new Thread(he);
Thread h2=new Thread(he);
Thread h3=new Thread(he);
h1.start();
h2.start();
h3.start();
}
private int count=5;
}
【同步代碼塊】：
語(yǔ)法格式：
synchronized（同步對(duì)象）{
//需要同步的代碼
}
但是一般都把當(dāng)前對(duì)象this作為同步對(duì)象。
比如對(duì)于上面的買票的問(wèn)題，如下：
public static void main(String[] args) {
hello he=new hello();
Thread h1=new Thread(he);
Thread h2=new Thread(he);
Thread h3=new Thread(he);
h1.start();
h2.start();
h3.start();
}
private int count=5;
}
public synchronized void sale() {
if (count > 0) {
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println(count--);
}
}
public static void main(String[] args) {
hello he = new hello();
Thread h1 = new Thread(he);
Thread h2 = new Thread(he);
Thread h3 = new Thread(he);
h1.start();
h2.start();
h3.start();
}
private int count = 5;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
private String name = "Rollen";
private int age = 20;
}
/**
* 生產(chǎn)者
* */
class Producer implements Runnable{
private Info info=null;
Producer(Info info){
this.info=info;
}
public void run(){
boolean flag=false;
for(int i=0;i<25;++i){
if(flag){
this.info.setName("Rollen");
try{
Thread.sleep(100);
}catch (Exception e) {
e.printStackTrace();
}
this.info.setAge(20);
flag=false;
}else{
this.info.setName("chunGe");
try{
Thread.sleep(100);
}catch (Exception e) {
e.printStackTrace();
}
this.info.setAge(100);
flag=true;
}
}
}
}
/**
* 消費(fèi)者類
* */
class Consumer implements Runnable{
private Info info=null;
public Consumer(Info info){
this.info=info;
}
public void run(){
for(int i=0;i<25;++i){
try{
Thread.sleep(100);
}catch (Exception e) {
e.printStackTrace();
}
System.out.println(this.info.getName()+"<---->"+this.info.getAge());
}
}
}
/**
* 測(cè)試類
* */
class hello{
public static void main(String[] args) {
Info info=new Info();
Producer pro=new Producer(info);
Consumer con=new Consumer(info);
new Thread(pro).start();
new Thread(con).start();
}
}
那么如何解決呢？
<!--[if !supportLists]-->1） <!--[endif]-->加入同步
<!--[if !supportLists]-->2） <!--[endif]-->加入等待和喚醒
先來(lái)看看加入同步會(huì)是如何。
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public synchronized void set(String name, int age){
this.name=name;
try{
Thread.sleep(100);
}catch (Exception e) {
e.printStackTrace();
}
this.age=age;
}
public synchronized void get(){
try{
Thread.sleep(100);
}catch (Exception e) {
e.printStackTrace();
}
System.out.println(this.getName()+"<===>"+this.getAge());
}
private String name = "Rollen";
private int age = 20;
}
/**
* 生產(chǎn)者
* */
class Producer implements Runnable {
private Info info = null;
Producer(Info info) {
this.info = info;
}
public void run() {
boolean flag = false;
for (int i = 0; i < 25; ++i) {
if (flag) {
this.info.set("Rollen", 20);
flag = false;
} else {
this.info.set("ChunGe", 100);
flag = true;
}
}
}
}
/**
* 消費(fèi)者類
* */
class Consumer implements Runnable {
private Info info = null;
public Consumer(Info info) {
this.info = info;
}
public void run() {
for (int i = 0; i < 25; ++i) {
try {
Thread.sleep(100);
} catch (Exception e) {
e.printStackTrace();
}
this.info.get();
}
}
}
/**
* 測(cè)試類
* */
class hello {
public static void main(String[] args) {
Info info = new Info();
Producer pro = new Producer(info);
Consumer con = new Consumer(info);
new Thread(pro).start();
new Thread(con).start();
}
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public synchronized void set(String name, int age){
if(!flag){
try{
super.wait();
}catch (Exception e) {
e.printStackTrace();
}
}
this.name=name;
try{
Thread.sleep(100);
}catch (Exception e) {
e.printStackTrace();
}
this.age=age;
flag=false;
super.notify();
}
public synchronized void get(){
if(flag){
try{
super.wait();
}catch (Exception e) {
e.printStackTrace();
}
}
try{
Thread.sleep(100);
}catch (Exception e) {
e.printStackTrace();
}
System.out.println(this.getName()+"<===>"+this.getAge());
flag=true;
super.notify();
}
private String name = "Rollen";
private int age = 20;
private boolean flag=false;
}
/**
* 生產(chǎn)者
* */
class Producer implements Runnable {
private Info info = null;
Producer(Info info) {
this.info = info;
}
public void run() {
boolean flag = false;
for (int i = 0; i < 25; ++i) {
if (flag) {
this.info.set("Rollen", 20);
flag = false;
} else {
this.info.set("ChunGe", 100);
flag = true;
}
}
}
}
/**
* 消費(fèi)者類
* */
class Consumer implements Runnable {
private Info info = null;
public Consumer(Info info) {
this.info = info;
}
public void run() {
for (int i = 0; i < 25; ++i) {
try {
Thread.sleep(100);
} catch (Exception e) {
e.printStackTrace();
}
this.info.get();
}
}
}
/**
* 測(cè)試類
* */
class hello {
public static void main(String[] args) {
Info info = new Info();
Producer pro = new Producer(info);
Consumer con = new Consumer(info);
new Thread(pro).start();
new Thread(con).start();
}
}
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