Why Thread.stop(), Thread.suspend(), and Thread.resume() Methods are Deprecated After JDK 1.1 Version

The Thread class offers constructors and functions for creating and controlling threads. It serves as a subclass of Objects and also implements the Runnable interface.

Deprecated methods are no longer considered significant and should not be used because they may be eliminated from the class in future versions. As classes evolve, their APIs change, which can involve renaming attributes, adding new methods, or modifying existing ones. To assist developers in migrating from the previous API to the new one, deprecated classes and methods are identified in documentation comments using the @deprecated tag.

Why were these methods marked as deprecated?

The methods Thread.stop(), Thread.suspend(), and Thread.resume() were deprecated after JDK 1.1 because they were deemed unsafe and potentially dangerous.

The Thread.stop() method was used to terminate a thread's execution forcefully. However, it abruptly terminates the thread's execution, potentially leaving the application or system inconsistent. The abrupt termination can also result in resource leaks or other undesirable consequences. Therefore, the Thread.stop() method was deprecated.

The Thread.suspend() method was used to suspend the execution of a thread temporarily. However, suspending a thread without its cooperation can lead to thread deadlock or other synchronization issues. If a thread is suspended while holding certain resources or locks, it can prevent other threads from accessing those resources, causing the entire application to become unresponsive. Its inherent risk led to the deprecation of the Thread.suspend() method.

The Thread.resume() method was used to resume the execution of a suspended thread. However, resuming a thread without proper synchronization can also lead to synchronization issues and thread deadlocks. Since the Thread.suspend() method was deprecated, the Thread.resume() method became unnecessary and deprecated.

Deadlock Using Deprecated Thread Synchronization Methods

In concurrent programming, deadlocks occur when multiple threads are blocked indefinitely, waiting for each other to release resources. The code example demonstrates a deadlock scenario using deprecated thread synchronization methods.

Filename: DeadlockUsingDeprecatedMethods.java

class DataHolder {
    private int[] data;
    private int index;

    public DataHolder() {
        data = new int[10];
        index = 0;
    }

    public void setValue(int value) {
        if (index < 9) {
            System.out.println("Setting value " + value + " in the data array");
            data[index] = value;
            index++;
        }
    }

    public int getValue() {
        if (index > 0) {
            index--;
            System.out.println("Returning value: " + data[index]);
            return data[index];
        } else {
            return -1;
        }
    }
}

class MyThread extends Thread {
    private DataHolder dataHolder;

    public MyThread(String threadName, DataHolder dataHolder) {
        super(threadName);
        this.dataHolder = dataHolder;
    }

    public void run() {
        synchronized (dataHolder) {
            int value = 0;
            while (value < 5) {
                System.out.println("Thread Name: " + Thread.currentThread().getName());
                value++;
                dataHolder.setValue(value);
                try {
                    Thread.sleep(100);
                    System.out.println(Thread.currentThread().getName() + " is awake now");
                } catch (InterruptedException e) {
                    System.out.println("Exception caught");
                }
                if (value == 2) {
                    try {
                        System.out.println(Thread.currentThread().getName() + " is suspending");
                        suspend();
                    } catch (SecurityException e) {
                        System.out.println("Exception caught while suspending thread");
                    }
                }
            }
        }
    }
}

public class DeadlockUsingDeprecatedMethods {
    public static void main(String[] args) {
        // Create a shared DataHolder object
        DataHolder dataHolder = new DataHolder();

        // Create two threads that operate on the same DataHolder object
        MyThread thread1 = new MyThread("Thread A", dataHolder);
        MyThread thread2 = new MyThread("Thread B", dataHolder);

        // Start the threads
        thread1.start();
        thread2.start();

        // Main thread performs its own operations
        for (int i = 500; i <= 501; i++) {
            System.out.println("Main Thread " + i);
        }
    }
}

Output:

Main Thread 500
Main Thread 501Thread Name: Thread A
Setting value 1 in the data array
Thread A is awake now
Thread Name: Thread A
Setting value 2 in the data array
Thread A is awake now
Thread A is suspending

Explanation: The provided code creates thread1 and thread2, which operate on a shared DataHolder object. The DataHolder class encapsulates an integer array and provides methods to set values in the array (setValue()) and retrieve values from it (getValue()).

Within each thread's run() method, a synchronized block ensures that only one thread can access the shared DataHolder object at a time. The threads increment a value, set it in the DataHolder using setValue(), and perform some processing. When the value reaches 2, the thread suspends itself using the deprecated suspend() method, potentially leading to a deadlock scenario.

The main thread starts thread1 and thread2 and then executes its operations concurrently. The code snippet serves as an example to demonstrate the potential issues and dangers associated with using deprecated methods like suspend().

It's important to note that suspend() and resume() methods for thread synchronization are discouraged due to their inherent risks, such as potential deadlocks and thread safety violations. Modern concurrency mechanisms like locks, semaphores, and condition variables provide safer alternatives for managing thread synchronization and communication.

Next TopicCircular Primes in Java

← prev next →