Thread-local storage (TLS) in multithreading

Each thread has its own instance of a map that stores thread-local variables.

This map holds the associations between the thread-local variables and their corresponding values, ensuring that the variables are unique to the thread and are not shared across other threads.

This allows threads to maintain

• isolated states,
• preventing race conditions and
• ensuring data consistency within each thread.

public static ThreadLocal<Student> studentThreadLocal = new ThreadLocal<Student>();

studentThreadLocal has the global scope, but the value inside the studentThreadLocal has the scope only for the duration of a thread

//Sets the current thread's value
studentThreadLocal.set(new Student("Harry Potter"));

//gets the current thread's value'
studentThreadLocal.get();

Inheritable ThreadLocal

InheritableThreadLocal is a subclass of ThreadLocal. It allows child threads to inherit the values of the parent thread.

• By Default child thread values are identical to Parent Thread.

When a child thread gets created the the local values of parent get copied over to the child in 2 ways

• Default copy is shallow copy (pointer to the original is saved with the child)
  • If the child thread sets a new value, parent thread will see the updated value

// InheritableThreadLocal variable
private static final InheritableThreadLocal<String> threadLocalValue = new InheritableThreadLocal<>();