我知道如何正确地做到这一点，但我想知道为什么这个代码会按照我的意愿运行，**没有任何明显的错误**，而如果我删除 Thread.sleep（100）; < / em>来自两个while循环的行，程序进入无限循环状态？
import java.util.Random;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.Random;
import java.util.Random;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
interface Buffer
{
// place int value into Buffer
public void set( int value ) throws InterruptedException;
// obtain int value from Buffer
public int get() throws InterruptedException;
} // end interface Buffer
public class javaapplication32
{
public static void main( String[] args )
{
// create new thread pool with two threads
ExecutorService application = Executors.newCachedThreadPool();
// create CircularBuffer to store ints
CircularBuffer sharedLocation = new CircularBuffer();
// display the initial state of the CircularBuffer
sharedLocation.displayState( "Initial State" );
// execute the Producer and Consumer tasks
application.execute( new Producer( sharedLocation ) );
application.execute( new Consumer( sharedLocation ) );
application.shutdown();
} // end main
}
// Consumer.java
// Consumer's run method loops ten times reading a value from buffer.
class Consumer implements Runnable
{
private final static Random generator = new Random();
private final Buffer sharedLocation; // reference to shared object
// constructor
public Consumer( Buffer shared )
{
sharedLocation = shared;
} // end Consumer constructor
// read sharedLocation's value 10 times and sum the values
public void run()
{
int sum = 0;
for ( int count = 1; count <= 10; count++ )
{
// sleep 0 to 3 seconds, read value from buffer and add to sum
try
{
Thread.sleep( generator.nextInt( 3000 ) );
sum += sharedLocation.get();
} // end try
// if lines 26 or 27 get interrupted, print stack trace
catch ( InterruptedException exception )
{
exception.printStackTrace();
} // end catch
} // end for
System.out.printf( "\n%s %d\n%s\n",
"Consumer read values totaling", sum, "Terminating Consumer" );
} // end method run
} // end class Consumer
class Producer implements Runnable
{
private final static Random generator = new Random();
private final Buffer sharedLocation; // reference to shared object
// constructor
public Producer( Buffer shared )
{
sharedLocation = shared;
} // end Producer constructor
// store values from 1 to 10 in sharedLocation
public void run()
{
int sum = 0;
for ( int count = 1; count <= 10; count++ )
{
try // sleep 0 to 3 seconds, then place value in Buffer
{
Thread.sleep( generator.nextInt( 3000 ) ); // sleep thread
sharedLocation.set( count ); // set value in buffer
sum += count; // increment sum of values
} // end try
// if lines 25 or 26 get interrupted, print stack trace
catch ( InterruptedException exception )
{
exception.printStackTrace();
} // end catch
} // end for
System.out.println(
"Producer done producing\nTerminating Producer" );
} // end method run
} // end class Producer
class CircularBuffer implements Buffer
{
private final int[] buffer = { -1, -1, -1 }; // shared buffer
private int occupiedCells = 0; // count number of buffers used
private int writeIndex = 0; // index of next element to write to
private int readIndex = 0; // index of next element to read
// place value into buffer
public void set( int value ) throws InterruptedException
{
// wait until buffer has space avaialble, then write value;
// while no empty locations, place thread in waiting state
while ( occupiedCells == buffer.length)
{
Thread.sleep(100);
} // end while
buffer[ writeIndex ] = value; // set new buffer value
// update circular write index
writeIndex = ( writeIndex + 1 ) % buffer.length;
++occupiedCells; // one more buffer cell is full
displayState( "Producer writes " + value );
// notifyAll(); // notify threads waiting to read from buffer
} // end method set
// return value from buffer
public int get() throws InterruptedException
{
// wait until buffer has data, then read value;
// while no data to read, place thread in waiting state
while (occupiedCells == 0 )
{
**Thread.sleep(100);**
} // end while
int readValue = buffer[ readIndex ]; // read value from buffer
// update circular read index
readIndex = ( readIndex + 1 ) % buffer.length;
--occupiedCells; // one fewer buffer cells are occupied
displayState( "Consumer reads " + readValue );
// notifyAll(); // notify threads waiting to write to buffer
return readValue;
} // end method get
// display current operation and buffer state
public void displayState( String operation )
{
// output operation and number of occupied buffer cells
System.out.printf( "%s%s%d)\n%s", operation,
" (buffer cells occupied: ", occupiedCells, "buffer cells: " );
for ( int value : buffer )
System.out.printf( " %2d ", value ); // output values in buffer
System.out.print( "\n " );
for ( int i = 0; i < buffer.length; i++ )
System.out.print( "---- " );
System.out.print( "\n " );
for ( int i = 0; i < buffer.length; i++ )
{
if ( i == writeIndex && i == readIndex )
System.out.print( " WR" ); // both write and read index
else if ( i == writeIndex )
System.out.print( " W " ); // just write index
else if ( i == readIndex )
System.out.print( " R " ); // just read index
else
System.out.print( " " ); // neither index
} // end for
System.out.println( "\n" );
} // end method displayState
}
我的问题不是如何正确地做到这一点，而是
答案 0 :(得分：2)
Thread.sleep用于减少不必要的CPU使用率。在没有睡眠的单核系统上可能会占用CPU时间的其他线程，因此可能需要很长时间才能离开自旋锁。在任何情况下，look into using wait() and notify()而不是实现自己的螺旋锁。
答案 1 :(得分：0)
我不相信它的无限，但它朝着这个方向前进。查看使用的处理器容量。只要两个线程在同一进程中运行，共享相同的处理器核心。我敢打赌，检查将获得所有资源......