Java 无法在多线程中实现同步
我基本上是在尝试实现一个现实生活中的例子,多人在线预订一辆出租车。在我的代码中,我有3个类-出租车、客户和服务器Java 无法在多线程中实现同步,java,multithreading,synchronization,java-threads,Java,Multithreading,Synchronization,Java Threads,我基本上是在尝试实现一个现实生活中的例子,多人在线预订一辆出租车。在我的代码中,我有3个类-出租车、客户和服务器必须有多个客户(线程)和一辆出租车。但我不能这么做。每次我创建新客户时,都会创建一个新的出租车实例。 这是出租车等级代码- public class taxi { boolean BOOKED=false; String id; void book(){ try { Th
必须有多个客户(线程)和一辆出租车。但我不能这么做。每次我创建新客户时,都会创建一个新的出租车实例。
这是出租车等级代码-
public class taxi {
boolean BOOKED=false;
String id;
void book(){
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
BOOKED=true;
System.out.println("Customer "+Thread.currentThread().getName()+" BOOKED taxi");
}
void release(){
BOOKED=false;
System.out.println("Customer "+Thread.currentThread().getName()+" RELEASED taxi");
}
void setId(String id){
this.id=id;
}
String getId(){
return id;
}
}
客户类别代码-
public class customer extends Thread {
taxi t=new taxi();
public void run(){
//System.out.println(t.hashCode());
t.setId(Thread.currentThread().getName());
System.out.println("Customer "+Thread.currentThread().getName()+" trying to BOOK taxi");
t.book();
System.out.println("Customer "+Thread.currentThread().getName()+" is currently USING taxi");
try {
Thread.sleep(2000);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
System.out.println("Customer "+Thread.currentThread().getName()+" RELEASING taxi");
t.release();
try {
Thread.sleep(3000);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
System.out.println("taxi used by customer "+Thread.currentThread().getName()+" set id to "+t.getId());
}
}
public class server {
public static void main(String args[]){
customer A=new customer();
customer B=new customer();
customer C=new customer();
customer D=new customer();
Thread t=new Thread();
A.setName("A");
B.setName("B");
C.setName("C");
D.setName("D");
A.start();
B.start();
C.start();
D.start();
}
}
服务器类代码-
public class customer extends Thread {
taxi t=new taxi();
public void run(){
//System.out.println(t.hashCode());
t.setId(Thread.currentThread().getName());
System.out.println("Customer "+Thread.currentThread().getName()+" trying to BOOK taxi");
t.book();
System.out.println("Customer "+Thread.currentThread().getName()+" is currently USING taxi");
try {
Thread.sleep(2000);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
System.out.println("Customer "+Thread.currentThread().getName()+" RELEASING taxi");
t.release();
try {
Thread.sleep(3000);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
System.out.println("taxi used by customer "+Thread.currentThread().getName()+" set id to "+t.getId());
}
}
public class server {
public static void main(String args[]){
customer A=new customer();
customer B=new customer();
customer C=new customer();
customer D=new customer();
Thread t=new Thread();
A.setName("A");
B.setName("B");
C.setName("C");
D.setName("D");
A.start();
B.start();
C.start();
D.start();
}
}
这是我的输出-
Customer B trying to BOOK taxi
Customer D trying to BOOK taxi
Customer A trying to BOOK taxi
Customer C trying to BOOK taxi
Customer B BOOKED taxi
Customer A BOOKED taxi
Customer A is currently USING taxi
Customer D BOOKED taxi
Customer D is currently USING taxi
Customer B is currently USING taxi
Customer C BOOKED taxi
Customer C is currently USING taxi
Customer C RELEASING taxi
Customer C RELEASED taxi
Customer D RELEASING taxi
Customer D RELEASED taxi
Customer A RELEASING taxi
Customer A RELEASED taxi
Customer B RELEASING taxi
Customer B RELEASED taxi
taxi used by customer D set id to D
taxi used by customer C set id to C
taxi used by customer A set id to A
taxi used by customer B set id to B
正如您所看到的,每辆出租车的id是不同的,而不是相同的。
请帮助。我认为,出租车等级不必是一条线索。通过将滑行类作为所有其他客户线程之间的共享资源(使用同步方法的单吨),我们可以在多线程中实现预期的同步。我认为,滑行类不必是线程。通过将滑行类作为所有其他客户线程之间的共享资源(单吨同步方法),我们可以在多线程中实现预期的同步。有关代码的一些要点:
public class Taxi {
Boolean BOOKED = false;
String id;
void book() throws InterruptedException {
synchronized (this) {
while (BOOKED) {
this.wait();
}
try {
setId(Thread.currentThread().getName());
} catch (InterruptedException e) {
e.printStackTrace();
}
BOOKED = true;
System.out.println("Customer " + Thread.currentThread().getName() + " BOOKED taxi");
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
void release() throws InterruptedException {
synchronized (this) {
BOOKED = false;
System.out.println("Customer " + Thread.currentThread().getName() + " RELEASED taxi");
this.notifyAll();
}
}
void setId(String id) throws InterruptedException {
System.out.println("SETTING ID TO CUSTOMER " + Thread.currentThread().getName());
this.id = id;
}
String getId() {
return id;
}
}
客户:
public class Customer extends Thread {
Taxi taxi;
public Customer(Taxi taxi){
this.taxi = taxi;
}
public void run(){
//System.out.println(t.hashCode());
System.out.println("Customer "+Thread.currentThread().getName()+" trying to BOOK taxi");
try {
taxi.book();
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println("Customer "+Thread.currentThread().getName()+" is currently USING taxi");
try {
Thread.sleep(2000);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
System.out.println("Customer "+Thread.currentThread().getName()+" RELEASING taxi");
try {
taxi.release();
} catch (InterruptedException e) {
e.printStackTrace();
}
try {
Thread.sleep(3000);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
关于代码的一些要点:
public class Taxi {
Boolean BOOKED = false;
String id;
void book() throws InterruptedException {
synchronized (this) {
while (BOOKED) {
this.wait();
}
try {
setId(Thread.currentThread().getName());
} catch (InterruptedException e) {
e.printStackTrace();
}
BOOKED = true;
System.out.println("Customer " + Thread.currentThread().getName() + " BOOKED taxi");
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
void release() throws InterruptedException {
synchronized (this) {
BOOKED = false;
System.out.println("Customer " + Thread.currentThread().getName() + " RELEASED taxi");
this.notifyAll();
}
}
void setId(String id) throws InterruptedException {
System.out.println("SETTING ID TO CUSTOMER " + Thread.currentThread().getName());
this.id = id;
}
String getId() {
return id;
}
}
客户:
public class Customer extends Thread {
Taxi taxi;
public Customer(Taxi taxi){
this.taxi = taxi;
}
public void run(){
//System.out.println(t.hashCode());
System.out.println("Customer "+Thread.currentThread().getName()+" trying to BOOK taxi");
try {
taxi.book();
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println("Customer "+Thread.currentThread().getName()+" is currently USING taxi");
try {
Thread.sleep(2000);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
System.out.println("Customer "+Thread.currentThread().getName()+" RELEASING taxi");
try {
taxi.release();
} catch (InterruptedException e) {
e.printStackTrace();
}
try {
Thread.sleep(3000);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
为什么每次在客户中创建新的出租车?问题是:
taxi t=new taxi()代码>。只需通过构造函数传递出租车,或使其成为全局的或类似的。这样,每位顾客都将乘坐同一辆出租车。此外,线程是危险的,所以你应该非常小心使用它们。您没有任何同步。我建议你不了解如何正确使用线程。我建议您阅读有关同步
,易失性
,等待
,通知
,通知所有
,并尝试一些基本示例。我觉得头两个在headfirstjava
中描述得很好。
Offtopic:在命名变量和方法时,应该遵循约定。为什么每次在客户中创建新的出租车时都要这样做?问题是:taxi t=new taxi()代码>。只需通过构造函数传递出租车,或使其成为全局的或类似的。这样,每位顾客都将乘坐同一辆出租车。此外,线程是危险的,所以你应该非常小心使用它们。您没有任何同步。我建议你不了解如何正确使用线程。我建议您阅读有关同步
,易失性
,等待
,通知
,通知所有
,并尝试一些基本示例。我觉得头两个在headfirstjava
中描述得很好。
Offtopic:在命名变量和方法时,应该遵循约定。您认为如何taxi t=new taxi()
是否作为customer
中的一个字段?它在customer中创建一个taxi实例。我知道这是我的问题的根本原因,但我想不出其他方法来解决这个问题。创建一个taxi
实例,并在您的客户
实例中共享。你以前学过构造函数参数吗?是的,我知道客户参数。您能告诉我执行此操作的确切代码吗?不幸的是,不能。请使用构造函数参数在每个customer
实例中设置taxi
字段。使用相同的taxi
实例作为您创建的每个客户的参数
是否作为customer
中的一个字段?它在customer中创建一个taxi实例。我知道这是我的问题的根本原因,但我想不出其他方法来解决这个问题。创建一个taxi
实例,并在您的客户
实例中共享。你以前学过构造函数参数吗?是的,我知道客户参数。您能告诉我执行此操作的确切代码吗?不幸的是,不能。请使用构造函数参数在每个customer
实例中设置taxi
字段。使用相同的taxi
实例作为您创建的每个customer
的参数。您能告诉我如何使用wait()和notify()等方法吗?您能告诉我如何使用wait()和notify()等方法吗?我想您误解了这个问题。这里的问题是,我最终拥有了多个taxi类实例,而且由于taxi类充当了我的数据,我不能拥有多个实例。您应该只创建一个taxi类实例,并从Customer类中删除taxi实例变量,然后在server ClassOK中实例化taxi。那么我如何进一步使用该实例,以便所有线程都在同一个实例上工作请看上面的答案,我猜您误解了这个问题。这里的问题是,我最终拥有了多个taxi类的实例,并且由于taxi类充当了我的数据,所以我不能拥有它的多个实例