An interesting topic: about multithreading! !!

kippakiss

I wrote this applet myself today

The requirements for this topic are:
There are 4 pairs of families: father, mother, son, daughter

Dads are responsible for putting apples on the plate, and moms are responsible for putting oranges on the plate.
Sons specialize in oranges on plates; daughters specialize in apples on plates;

Note; there can be no more than 10 fruits on the plate, and only one fruit can be placed or taken at a time;

That's all, the code is below, and there are some problems in running. It seems that sometimes some methods are accessed multiple times.
If you are interested, you can run the code and help me analyze the reason, thank you
class ThreadTest
{
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public static void main (String [] args)
{
Plate q = new Plate ();
Father f1 = new Father (q);
Father f2 = new Father (q);
Father f3 = new Father (q);
Father f4 = new Father (q);
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Mother m1 = new Mother (q);
Mother m2 = new Mother (q);
Mother m3 = new Mother (q);
Mother m4 = new Mother (q);
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Son s1 = new Son (q);
Son s2 = new Son (q);
Son s3 = new Son (q);
Son s4 = new Son (q);
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Daughter d1 = new Daughter (q);
Daughter d2 = new Daughter (q);
Daughter d3 = new Daughter (q);
Daughter d4 = new Daughter (q);
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f1.start ();
f2.start ();
f3.start ();
f4.start ();
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m1.start ();
m2.start ();
m3.start ();
m4.start ();
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s1.start ();
s2.start ();
s3.start ();
s4.start ();
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d1.start ();
d2.start ();
d3.start ();
d4.start ();
}
}

class Father extends Thread
{
Plate q;
Father (Plate q)
{
this.q = q;
}
public void run ()
{
while (true)
{
q.putApple (q.apple);
System.out.println (Thread.currentThread (). GetName () + "put one apple:

the number of apple in the plate: "+ q.apple);
}
}
}
class Mother extends Thread
{
Plate q;
Mother (Plate q)
{
this.q = q;
}
public void run ()
{
while (true)
{
q.putOrange (q.orange);
System.out.println (Thread.currentThread (). GetName () + "put one

orange: the number of orange in the plate: "+ q.orange);
}
}
}
class Son extends Thread
{
Plate q;
Son (Plate q)
{
this.q = q;
}
public void run ()
{
while (true)
{
System.out.println (Thread.currentThread (). GetName () + "get one orange: the

number of orange in the plate: "+ q.getOrange ());
}
}
}
class Daughter extends Thread
{
Plate q;
Daughter (Plate q)
{
this.q = q;
}
public void run ()
{
while (true)
{
System.out.println (Thread.currentThread (). GetName () + "Daughter get one

apple: the number of apple in the plate: "+ q.getApple ());
}
}
}
class Plate
{
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int apple = 0;
int orange = 0;
int pFull = 10;
public synchronized void putApple (int i)
{
if (pFull <11&&pFull> 0)
{
i ++;
apple = i;
pFull--;
notifyAll ();
}
try
{
wait ();
}
catch (Exception e)
{
e.printStackTrace ();
}
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}
public synchronized int getApple ()
{
if (apple <1 || apple> 10)
{
try
{
wait ();
}
catch (Exception e)
{
e.printStackTrace ();
}
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}
pFull ++;
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notifyAll ();
apple--;
return apple;
}
public synchronized void putOrange (int i)
{
if (pFull <11&&pFull> 0)
{
i ++;
orange = i;
pFull--;
notifyAll ();
}
try
{
wait ();
}
catch (Exception e)
{
e.printStackTrace ();
}
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}
public synchronized int getOrange ()
{
while (orange <1 || orange> 11)
{
try
{
wait ();
}
catch (Exception e)
{
e.printStackTrace ();
}
}
pFull ++;
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notifyAll ();
orange--;
return orange;
}
}

seakey

UP down

liuxiangdo84

UP down

kippakiss

Can anyone help explain the following?

beichihwfs

mark

hikerlove

up

hikerlove

Although your get and set methods are synchronous, the two get and two set methods can be performed at the same time, resulting in a pfull of -1 and eventually all threads deadlock.

cmqtxy@163.com

Very good, learn! !! !!

kippakiss

How do I need to change it to get the two get methods or set methods?

It's forbidden to do both

Suggestions, thank you

上帝的耳语

Use a Vector that stores orange or apple objects (when size () <10), synchronized when using Vector