Can the cause of system hangs be explained and how does it affect the application's performance?

A deadlock occurs when two or more threads or processes block each other, waiting for resources held by the other. For example, thread A holds resource 1 and waits for resource 2, while thread B holds resource 2 and waits for resource 1. As a result, neither thread can continue.

This leads to the application becoming unresponsive or malfunctioning, as the threads are in a state of infinite waiting. In multithreaded Java applications, deadlocks can cause the user interface to freeze, reduce performance, and even crash the system.

To prevent deadlocks, it is important to:

• Avoid nested locks or use them in a strictly defined order.
• Use timeouts when acquiring locks.
• Apply high-level synchronization constructs such as java.util.concurrent.

An example of a simple deadlock in Java:

public class DeadlockDemo {
    private final Object resource1 = new Object();
    private final Object resource2 = new Object();

    public void method1() {
        synchronized(resource1) {
            try { Thread.sleep(100); } catch (InterruptedException e) {}
            synchronized(resource2) {
                System.out.println("Method1 acquired both resources");
            }
        }
    }

    public void method2() {
        synchronized(resource2) {
            try { Thread.sleep(100); } catch (InterruptedException e) {}
            synchronized(resource1) {
                System.out.println("Method2 acquired both resources");
            }
        }
    }
}

If two threads call method1 and method2 simultaneously, a deadlock may occur.