이 글은 주로 자바 멀티스레드 기아 문제에 대한 해결책 관련 정보를 소개합니다. 필요한 친구들이 참고하면 됩니다.
자바 멀티스레드 기아 문제에 대한 해결책
스레드가 읽기, 아니요 쓰기 스레드의 쓰기는 허용하지만 다른 읽기 스레드의 읽기는 허용합니다. 쓰기 스레드가 쓰는 동안 다른 스레드는 읽거나 쓸 수 없습니다. 쓰기 스레드가 고갈되는 것을 방지하기 위해 스레드가 읽을 때 쓰기 스레드가 쓰기를 요청하면 후속 읽기 스레드는 읽기를 금지해야 합니다.
구현 코드는 다음과 같습니다.
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();
}
}
}작가 .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();
}
}
}프로그램 부분 실행 결과는 다음과 같습니다.
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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