java 多线程饥饿现象的问题解决方法
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2023-12-17 17:07:46
java 多线程饥饿现象的问题解决方法
当有线程正在读的时候，不允许写 线程写，但是允许其他的读线程进行读。有写线程正在写的时候，其他的线程不应该读写。为了防止写线程出现...
java 多线程饥饿现象的问题解决方法
当有线程正在读的时候，不允许写 线程写，但是允许其他的读线程进行读。有写线程正在写的时候，其他的线程不应该读写。为了防止写线程出现饥饿现象，当线程正在读，如果写线程请求写，那么应该禁止再来的读线程进行读。
实现代码如下：
file.java
package readerwriter;
public class file {
private string name;
public file(string name)
{
this.name=name;
}
}
pool.java
package readerwriter;
public class pool {
private int readernumber=0;
private int writernumber=0;
private boolean waittingwriten;
public boolean iswaittingwriten() {
return waittingwriten;
}
public void setwaittingwriten(boolean waittingwriten) {
this.waittingwriten = waittingwriten;
}
public file getfile() {
return file;
}
public void setfile(file file) {
this.file = file;
}
file file;
public pool(file file)
{
this.file=file;
}
public int getreadernumber() {
return readernumber;
}
public void setreadernumber(int readernumber) {
this.readernumber = readernumber;
}
public int getwriternumber() {
return writernumber;
}
public void setwriternumber(int writernumber) {
this.writernumber = writernumber;
}
}
reader.java
package readerwriter;
public class reader implements runnable{
private string id;
private pool pool;
public reader(string id,pool pool)
{
this.id=id;
this.pool=pool;
}
@override
public void run()
{
// todo auto-generated method stub
while(!thread.currentthread().interrupted()){
synchronized(pool){
while(pool.getwriternumber()>0 || pool.iswaittingwriten()==true)//当线程正在写或者
//有线程正在等待写，则禁止读线程继续读
{
try {
pool.wait();
} catch (interruptedexception e) {
// todo auto-generated catch block
e.printstacktrace();
}
}
{
pool.setreadernumber(pool.getreadernumber()+1);
}
}
system.out.println(id+" "+"is reading....");
try {
thread.sleep(1000);
} catch (interruptedexception e) {
// todo auto-generated catch block
e.printstacktrace();
}
synchronized(pool)
{
pool.setreadernumber(pool.getreadernumber()-1);
system.out.println(id+" "+"is existing the reader....");
if(pool.getreadernumber()==0)
pool.notifyall();
} try {
thread.sleep(1000);
} catch (interruptedexception e) {
// todo auto-generated catch block
e.printstacktrace();
}
// pool.notifyall();
}
}
}
writer.java
package readerwriter;
public class writer implements runnable{
private pool pool;
string id;
public writer(string id,pool pool)
{
this.id=id;
this.pool=pool;
}
@override
public void run() {
// todo auto-generated method stub
while(!thread.currentthread().interrupted()){
synchronized(pool){
if(pool.getreadernumber()>0)
pool.setwaittingwriten(true);
else
pool.setwaittingwriten(false);
//当线程正在被读或者被写或者有线程等待读
while(pool.getwriternumber()>0 || pool.getreadernumber()>0)
{
try {
pool.wait();
} catch (interruptedexception e) {
// todo auto-generated catch block
e.printstacktrace();
}
}
pool.setwaittingwriten(false); //这个策略还算公平
{
pool.setwriternumber(pool.getwriternumber()+1);
}
}
system.out.println(id+" "+"is writing....");
try {
thread.sleep(1000);
} catch (interruptedexception e) {
// todo auto-generated catch block
e.printstacktrace();
}
//
synchronized(pool)
{
pool.setwriternumber(pool.getwriternumber()-1);
system.out.println(id+" "+"is existing the writer....");
pool.notifyall();
}
/* try {
thread.sleep(1000);
//system.out.println("writer sleeping over");
} catch (interruptedexception e) {
// todo auto-generated catch block
e.printstacktrace();
} */
}
}
}
main.java
package readerwriter;
public class main {
public static void main(string[] args) {
// todo auto-generated method stub
pool pool=new pool(new file("dd file"));
for(int i=0;i<2;i++)
{
thread writer=new thread(new writer("writer "+i,pool));
writer.start();
}
for(int i=0;i<5;i++)
{
thread reader=new thread(new reader("reader "+i,pool));
reader.start();
}
}
}
程序部分运行结果如下：
writer 0 is writing.... writer 0 is existing the writer.... writer 0 is writing.... writer 0 is existing the writer.... writer 0 is writing.... writer 0 is existing the writer.... writer 0 is writing.... writer 0 is existing the writer.... writer 1 is writing.... writer 1 is existing the writer.... writer 1 is writing.... writer 1 is existing the writer.... writer 1 is writing.... writer 1 is existing the writer.... writer 1 is writing.... writer 1 is existing the writer.... writer 0 is writing.... writer 0 is existing the writer.... writer 0 is writing.... writer 0 is existing the writer.... reader 0 is reading.... reader 0 is existing the reader.... writer 1 is writing.... writer 1 is existing the writer.... writer 1 is writing.... writer 1 is existing the writer.... writer 1 is writing.... writer 1 is existing the writer.... writer 1 is writing.... writer 1 is existing the writer.... writer 1 is writing.... writer 1 is existing the writer.... writer 0 is writing.... writer 0 is existing the writer.... writer 0 is writing.... writer 0 is existing the writer.... writer 0 is writing.... writer 0 is existing the writer.... writer 0 is writing.... writer 0 is existing the writer.... reader 3 is reading.... reader 2 is reading.... reader 4 is reading.... reader 1 is reading.... reader 0 is reading.... reader 3 is existing the reader.... reader 1 is existing the reader.... reader 0 is existing the reader.... reader 4 is existing the reader.... reader 2 is existing the reader.... writer 0 is writing.... writer 0 is existing the writer.... writer 0 is writing.... writer 0 is existing the writer.... writer 1 is writing.... writer 1 is existing the writer.... reader 2 is reading.... reader 2 is existing the reader.... writer 0 is writing.... writer 0 is existing the writer.... writer 0 is writing.... writer 0 is existing the writer.... writer 0 is writing....
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