Início / coding / Perguntas / 76922470
Accepted
Kris Jobs
Asked: 2023-08-17 22:27:28 +0800 CST

Lock Condition.notify está lançando java.lang.IllegalMonitorStateException

  • 772

Eu escrevi um programa para demonstrar Lock.Condition de java para fins de multithreading. Estou recebendo IllegalMonitorStateException.

Está lançando uma exceção abaixo é a saída.

Estou adquirindo o bloqueio antes de chamar a notificação em uma condição. Mas ainda recebendo o erro abaixo. Alguém pode ajudar. Pesquisei bastante no Google mas não consegui encontrar uma solução.

Count : 0
lock java.util.concurrent.locks.ReentrantLock@4ce4d37e[Locked by thread Thread-0]
Exception in thread "Thread-0" java.lang.IllegalMonitorStateException: current thread is not owner
at java.base/java.lang.Object.notify(Native Method)
at test.OddEvenPrinter.printEven(Test.java:51)
    at test.Test.lambda$main$1(Test.java:22)
at java.base/java.lang.Thread.run(Thread.java:1589)
Count : 1
lock java.util.concurrent.locks.ReentrantLock@4ce4d37e[Locked by thread Thread-1]
Exception in thread "Thread-1" java.lang.IllegalMonitorStateException: current thread is not owner
    at java.base/java.lang.Object.notify(Native Method)
    at test.OddEvenPrinter.printOdd(Test.java:67)
    at test.Test.lambda$main$0(Test.java:14)
    at java.base/java.lang.Thread.run(Thread.java:1589)

O código para isso está abaixo:

package test;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;
public class Test {
    public static void main(String[] args) {
        final OddEvenPrinter oddEvenPrinter = new OddEvenPrinter();
        Runnable oddRunnable = () -> {
            try {
                while (true)
                    oddEvenPrinter.printOdd();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        };
        Runnable evenRunnable = () -> {
            try {
                while (true)
                    oddEvenPrinter.printEven();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        };
        new Thread(evenRunnable).start();
        new Thread(oddRunnable).start();
    }
}

class OddEvenPrinter {
    private final Lock lock = new ReentrantLock();
    private final Condition oddPrint = lock.newCondition();
    private final Condition evenPrint = lock.newCondition();
    private int count;
    public void printEven() throws InterruptedException {
        lock.lock();
        try {
            Thread.sleep(3000);
            while (count % 2 == 1) {
                evenPrint.await();
            }
            System.out.println("Count : " + count++);
            System.out.println("lock " + lock);
            oddPrint.notify();
        } finally {
            lock.unlock();
        }
    }
    public void printOdd() throws InterruptedException {
        lock.lock();
        try {
            Thread.sleep(2000);
            while (count % 2 == 0) {
                oddPrint.await();
            }
            System.out.println("Count : " + count++);
            System.out.println("lock " + lock);
            evenPrint.notify();
        } finally {
            lock.unlock();
        }
    }
}
java

2 respostas

  1. Best Answer

    Ao usar, java.util.concurrent.locks.Conditiondevemos usar signalou signalAllmétodos.

    Exemplo:

    public void foo() {
    reentrantLock.lock();
    try {
        condition.signal();
    } finally {
        reentrantLock.unlock();
    }
}

    O notifye notifyAllsão os métodos relacionados aos bloqueios intrínsecos (com a synchronizedpalavra-chave), exemplo:

    public synchronized void foo() throws InterruptedException {
    this.notify();
}
    • 2

  2. Eu usei a notificação em vez do método de sinal quando estou usando condições de bloqueio.

    Estou colando o código corrigido para referência futura.

    package test;

import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;

public class Test {

    public static void main(String[] args) {
        final OddEvenPrinter oddEvenPrinter = new OddEvenPrinter();
        Runnable oddRunnable = () -> {
            try {
                while (true)
                    oddEvenPrinter.printOdd();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        };
        Runnable evenRunnable = () -> {
            try {
                while (true)
                    oddEvenPrinter.printEven();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        };
        new Thread(evenRunnable).start();
        new Thread(oddRunnable).start();
    }
}

class OddEvenPrinter {

    private final Lock lock = new ReentrantLock();

    private final Condition oddPrint = lock.newCondition();

    private final Condition evenPrint = lock.newCondition();

    private int count;

    public void printEven() throws InterruptedException {
        lock.lock();
        try {
            Thread.sleep(3000);
            while (count % 2 == 1) {
                evenPrint.await();
            }
            System.out.println("Count : " + count++);
            System.out.println("lock " + lock);
            oddPrint.signal();
        } finally {
            lock.unlock();
        }

    }

    public void printOdd() throws InterruptedException {
        lock.lock();
        try {
            Thread.sleep(2000);
            while (count % 2 == 0) {
                oddPrint.await();
            }
            System.out.println("Count : " + count++);
            System.out.println("lock " + lock);
            evenPrint.signal();
        } finally {
            lock.unlock();
        }

    }
}
    • 2

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