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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 FileString 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 setWaittingWritenboolean waittingWriten) {
this.waittingWriten = waittingWriten;
}
public File getFile) {
return file;
}
public void setFileFile file) {
this.file = file;
}
File file;
public PoolFile file)
{
this.file=file;
}
public int getReaderNumber) {
return readerNumber;
}
public void setReaderNumberint readerNumber) {
this.readerNumber = readerNumber;
}
public int getWriterNumber) {
return writerNumber;
}
public void setWriterNumberint writerNumber) {
this.writerNumber = writerNumber;
}
}
Reader.java
package readerWriter;
public class Reader implements Runnable{
private String id;
private Pool pool;
public ReaderString id,Pool pool)
{
this.id=id;
this.pool=pool;
}
@Override
public void run)
{
// TODO Auto-generated method stub
while!Thread.currentThread).interrupted)){
synchronizedpool){
whilepool.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.setReaderNumberpool.getReaderNumber)+1);
}
}
System.out.printlnid+" "+"is reading....");
try {
Thread.sleep1000);
} catch InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace);
}
synchronizedpool)
{
pool.setReaderNumberpool.getReaderNumber)-1);
System.out.printlnid+" "+"is existing the reader....");
ifpool.getReaderNumber)==0)
pool.notifyAll);
} try {
Thread.sleep1000);
} 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 WriterString id,Pool pool)
{
this.id=id;
this.pool=pool;
}
@Override
public void run) {
// TODO Auto-generated method stub
while!Thread.currentThread).interrupted)){
synchronizedpool){
ifpool.getReaderNumber)>0)
pool.setWaittingWritentrue);
else
pool.setWaittingWritenfalse);
//当线程正在被读或者被写或者有线程等待读
whilepool.getWriterNumber)>0 || pool.getReaderNumber)>0)
{
try {
pool.wait);
} catch InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace);
}
}
pool.setWaittingWritenfalse); //这个策略还算公平
{
pool.setWriterNumberpool.getWriterNumber)+1);
}
}
System.out.printlnid+" "+"is writing....");
try {
Thread.sleep1000);
} catch InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace);
}
//
synchronizedpool)
{
pool.setWriterNumberpool.getWriterNumber)-1);
System.out.printlnid+" "+"is existing the writer....");
pool.notifyAll);
}
/* try {
Thread.sleep1000);
//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 mainString[] args) {
// TODO Auto-generated method stub
Pool pool=new Poolnew File"dd file"));
forint i=0;i<2;i++)
{
Thread writer=new Threadnew Writer"writer "+i,pool));
writer.start);
}
forint i=0;i<5;i++)
{
Thread reader=new Threadnew 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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