Java におけるマルチスレッド スタベーション現象の問題と解決策
- 零下一度オリジナル
- 2017-06-17 11:37:012519ブラウズ
この記事は主に、Java マルチスレッド スターベーションの問題の解決策に関する関連情報を紹介します。必要な友人はそれを参照してください
Java マルチスレッド スターベーションの問題の解決策
reading、no 書き込みスレッドには書き込みを許可しますが、他の読み取りスレッドには読み取りを許可します。書き込みスレッドが書き込みを行っている間、他のスレッドは読み取りまたは書き込みを行うべきではありません。書き込みスレッドが枯渇するのを防ぐために、スレッドが読み取り中に、書き込みスレッドが書き込みを要求した場合、後続の読み取りスレッドは読み取りを禁止する必要があります。
実装コードは次のとおりです:
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();
}
}
}
ライター.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();
}
}
}
プログラムの部分的な実行結果は次のとおりです:
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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