In programming, especially in multi-threaded environments, thread-safe and non-thread-safe are terms used to describe whether code, objects, or functions can be safely accessed by multiple threads concurrently without causing unexpected behavior.

Key Differences:

  1. Thread-Safe:
    • Ensures that multiple threads can access shared resources (like variables, data structures, or functions) without causing race conditions or data inconsistency.
    • Uses techniques like locks, mutexes, or synchronization mechanisms to manage concurrent access.
    • Thread-safe code may be slower due to added overhead but is more reliable in concurrent environments.
    • Example: The StringBuffer class in Java is thread-safe due to its use of synchronized methods.
  2. Non-Thread-Safe:
    • Does not provide built-in mechanisms to manage concurrent access, meaning multiple threads can modify data at the same time, leading to unpredictable results.
    • Generally faster due to lack of synchronization overhead but risky in multi-threaded environments.
    • Suitable for single-threaded applications or when the programmer controls thread access to shared resources.
    • Example: The StringBuilder class in Java is not thread-safe but is faster than StringBuffer because it lacks synchronization.

Example Scenario:

Imagine a banking application where two threads try to withdraw money from the same account. If the withdrawal function is non-thread-safe, both threads might access the account balance at the same time, leading to incorrect balance updates. If the function is thread-safe, one thread will complete its operation first before the other can access the balance, ensuring accuracy.