java 多线程饥饿现象的问题解决方法
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
packagereaderWriter;
publicclassFile{
privateStringname;
publicFile(Stringname)
{
this.name=name;
}
}
Pool.java
packagereaderWriter;
publicclassPool{
privateintreaderNumber=0;
privateintwriterNumber=0;
privatebooleanwaittingWriten;
publicbooleanisWaittingWriten(){
returnwaittingWriten;
}
publicvoidsetWaittingWriten(booleanwaittingWriten){
this.waittingWriten=waittingWriten;
}
publicFilegetFile(){
returnfile;
}
publicvoidsetFile(Filefile){
this.file=file;
}
Filefile;
publicPool(Filefile)
{
this.file=file;
}
publicintgetReaderNumber(){
returnreaderNumber;
}
publicvoidsetReaderNumber(intreaderNumber){
this.readerNumber=readerNumber;
}
publicintgetWriterNumber(){
returnwriterNumber;
}
publicvoidsetWriterNumber(intwriterNumber){
this.writerNumber=writerNumber;
}
}
Reader.java
packagereaderWriter;
publicclassReaderimplementsRunnable{
privateStringid;
privatePoolpool;
publicReader(Stringid,Poolpool)
{
this.id=id;
this.pool=pool;
}
@Override
publicvoidrun()
{
//TODOAuto-generatedmethodstub
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(InterruptedExceptione){
//TODOAuto-generatedcatchblock
e.printStackTrace();
}
}
{
pool.setReaderNumber(pool.getReaderNumber()+1);
}
}
System.out.println(id+""+"isreading....");
try{
Thread.sleep(1000);
}catch(InterruptedExceptione){
//TODOAuto-generatedcatchblock
e.printStackTrace();
}
synchronized(pool)
{
pool.setReaderNumber(pool.getReaderNumber()-1);
System.out.println(id+""+"isexistingthereader....");
if(pool.getReaderNumber()==0)
pool.notifyAll();
}try{
Thread.sleep(1000);
}catch(InterruptedExceptione){
//TODOAuto-generatedcatchblock
e.printStackTrace();
}
//pool.notifyAll();
}
}
}
Writer.java
packagereaderWriter;
publicclassWriterimplementsRunnable{
privatePoolpool;
Stringid;
publicWriter(Stringid,Poolpool)
{
this.id=id;
this.pool=pool;
}
@Override
publicvoidrun(){
//TODOAuto-generatedmethodstub
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(InterruptedExceptione){
//TODOAuto-generatedcatchblock
e.printStackTrace();
}
}
pool.setWaittingWriten(false);//这个策略还算公平
{
pool.setWriterNumber(pool.getWriterNumber()+1);
}
}
System.out.println(id+""+"iswriting....");
try{
Thread.sleep(1000);
}catch(InterruptedExceptione){
//TODOAuto-generatedcatchblock
e.printStackTrace();
}
//
synchronized(pool)
{
pool.setWriterNumber(pool.getWriterNumber()-1);
System.out.println(id+""+"isexistingthewriter....");
pool.notifyAll();
}
/*try{
Thread.sleep(1000);
//System.out.println("writersleepingover");
}catch(InterruptedExceptione){
//TODOAuto-generatedcatchblock
e.printStackTrace();
}*/
}
}
}
Main.java
packagereaderWriter;
publicclassMain{
publicstaticvoidmain(String[]args){
//TODOAuto-generatedmethodstub
Poolpool=newPool(newFile("ddfile"));
for(inti=0;i<2;i++)
{
Threadwriter=newThread(newWriter("writer"+i,pool));
writer.start();
}
for(inti=0;i<5;i++)
{
Threadreader=newThread(newReader("reader"+i,pool));
reader.start();
}
}
}
程序部分运行结果如下：
writer0iswriting.... writer0isexistingthewriter.... writer0iswriting.... writer0isexistingthewriter.... writer0iswriting.... writer0isexistingthewriter.... writer0iswriting.... writer0isexistingthewriter.... writer1iswriting.... writer1isexistingthewriter.... writer1iswriting.... writer1isexistingthewriter.... writer1iswriting.... writer1isexistingthewriter.... writer1iswriting.... writer1isexistingthewriter.... writer0iswriting.... writer0isexistingthewriter.... writer0iswriting.... writer0isexistingthewriter.... reader0isreading.... reader0isexistingthereader.... writer1iswriting.... writer1isexistingthewriter.... writer1iswriting.... writer1isexistingthewriter.... writer1iswriting.... writer1isexistingthewriter.... writer1iswriting.... writer1isexistingthewriter.... writer1iswriting.... writer1isexistingthewriter.... writer0iswriting.... writer0isexistingthewriter.... writer0iswriting.... writer0isexistingthewriter.... writer0iswriting.... writer0isexistingthewriter.... writer0iswriting.... writer0isexistingthewriter.... reader3isreading.... reader2isreading.... reader4isreading.... reader1isreading.... reader0isreading.... reader3isexistingthereader.... reader1isexistingthereader.... reader0isexistingthereader.... reader4isexistingthereader.... reader2isexistingthereader.... writer0iswriting.... writer0isexistingthewriter.... writer0iswriting.... writer0isexistingthewriter.... writer1iswriting.... writer1isexistingthewriter.... reader2isreading.... reader2isexistingthereader.... writer0iswriting.... writer0isexistingthewriter.... writer0iswriting.... writer0isexistingthewriter.... writer0iswriting....
感谢阅读，希望能帮助到大家，谢谢大家对本站的支持！