我在一个多线程程序中工作。线程在一个矩阵 (workerThread) 中工作，我有一个打印矩阵状态的线程(显示)。我得到这个异常， 在 Matrix 类的 increaseRow() 中的 line monitor.signal()
有人可以告诉我，怎么了？
public class Matrix {
private int row;
private int column;
private int[][] matrix;
private Map<Integer, String> mapForRow;
private Map<Integer, String> mapForColumn;
private Lock lock;
private Condition condition;
private Condition monitor;
private boolean rowIncreased;
private boolean columnIncreased;
private boolean columnCanBeAdded;
private boolean rowCanBeAdded;
private boolean print;
public Matrix(int row, int column) {
this.matrix = new int[row][column];
lock = new ReentrantLock();
mapForColumn = new LinkedHashMap<Integer, String>();
mapForRow = new LinkedHashMap<Integer, String>();
condition = lock.newCondition();
monitor = lock.newCondition();
rowIncreased = false;
columnIncreased = false;
rowCanBeAdded = false;
columnCanBeAdded = false;
print = false;
}
public void increaseRow(int row) {
if (!mapForRow.containsKey(row))
mapForRow.put(row, "not increased");
if (mapForRow.get(row).equals("not increased") && !columnIncreased) {
mapForRow.get(row).equals("increased");
rowIncreased = true;
for (int j = 0; j < matrix.length; j++)
setMatrix(row, j, matrix[row][j] + 1);
mapForRow.put(row, "not increased");
rowIncreased = false;
print = true;
monitor.signal();
}
}
public void increaseColumn(int column) {
if (!mapForColumn.containsKey(column))
mapForColumn.put(column, "not increased");
if (mapForColumn.get(column).equals("not increased") && !rowIncreased) {
mapForColumn.get(column).equals("increased");
columnIncreased = true;
for (int i = 0; i < matrix.length; i++)
setMatrix(i, column, matrix[i][column] + 1);
mapForColumn.put(column, "not increased");
columnIncreased = false;
print = true;
monitor.signal();
}
}
public int sumColumn(int column) {
lock.lock();
int sum = 0;
try {
columnCanBeAdded = false;
while (columnIncreased || rowIncreased || rowCanBeAdded) {
condition.await();
}
for (int i = 0; i < matrix.length; i++)
sum += matrix[i][column];
columnCanBeAdded = true;
} catch (Exception e) {
e.printStackTrace();
} finally {
lock.unlock();
}
condition.signalAll();
print = true;
monitor.signal();
return sum;
}
public int sumRow(int row) {
lock.lock();
int sum = 0;
try {
rowCanBeAdded = false;
while (columnIncreased || rowIncreased || columnCanBeAdded) {
condition.await();
}
for (int j = 0; j < matrix.length; j++)
sum += matrix[row][j];
rowCanBeAdded = true;
} catch (Exception e) {
e.printStackTrace();
} finally {
lock.unlock();
}
condition.signalAll();
print = true;
monitor.signal();
return sum;
}
public void printMatrix() {
lock.lock();
try {
while (!print) {
monitor.await();
}
System.out.println("begin print matrix");
for (int i = 0; i < row; i++) {
System.out.println();
for (int j = 0; j < column; j++)
System.out.print(matrix[i][j]);
}
System.out.println("end print matrix");
print = false;
} catch (Exception e) {
e.printStackTrace();
} finally {
lock.unlock();
}
}
public void setMatrix(int row, int column, int number) {
matrix[row][column] = number;
}
public static void main(String[] args) {
Matrix matrix = new Matrix(10, 10);
for (int i = 0; i < 10; i++)
for (int j = 0; j < 10; j++)
matrix.setMatrix(i, j, 0);
for (int i = 0; i < 10; i++) {
WorkerThread workerThread = new WorkerThread(matrix);
workerThread.start();
}
// print the matrix state
Display display = new Display(matrix);
display.start();
}
}
显示类:
public class Display extends Thread {
private Matrix matrix;
public Display(Matrix matrix) {
this.matrix = matrix;
}
@Override
public void run() {
while(true)
matrix.printMatrix();
}
}
workerThread 类:
public class WorkerThread extends Thread {
private Matrix matrix;
public WorkerThread(Matrix matrix) {
this.matrix = matrix;
}
@Override
public void run() {
// prevent thread to die
while (true) {
matrix.increaseColumn(new Random().nextInt(9));
matrix.increaseRow(new Random().nextInt(9));
try {
sleep(2000);
} catch (InterruptedException e) {
e.printStackTrace();
}
matrix.sumRow(new Random().nextInt(9));
matrix.sumColumn(new Random().nextInt(9));
}
}
}
更新
Exception in thread "Thread-7" Exception in thread "Thread-6" Exception in thread "Thread-4" Exception in thread "Thread-1" Exception in thread "Thread-5" Exception in thread "Thread-9" Exception in thread "Thread-0" Exception in thread "Thread-2" Exception in thread "Thread-3" Exception in thread "Thread-8" java.lang.IllegalMonitorStateException
at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.signal(AbstractQueuedSynchronizer.java:1941)
at Matrix.increaseColumn(Matrix.java:67)
at WorkerThread.run(WorkerThread.java:15)
java.lang.IllegalMonitorStateException
at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.signal(AbstractQueuedSynchronizer.java:1941)
at Matrix.increaseColumn(Matrix.java:67)
at WorkerThread.run(WorkerThread.java:15)begin print matrix
end print matrix
最佳答案
是的，问题是在 increaseRow 中，您调用 monitor.signal() 时没有先锁定 lock。来自 Condition.signal() 的文档:
您的 increaseRow 和 increaseColumn 方法都应该具有以下结构
lock.lock();
try {
// code including monitor.signal() here
} finally {
lock.unlock();
}
就像您的
sumRow 、 sumColumn 和 printMatrix 方法一样。或者，您可能希望为每一行和每一列设置一个单独的监视器(和条件)。您基本上需要考虑所有并发约束——如果不了解您要实现的目标，就很难提供更多指导。关于调用signal()时抛出java.lang.IllegalMonitorStateException，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/26384304/