What is the purpose of the volatile keyword in Java?

The volatile keyword in Java is used to indicate that a variable's value may be modified by multiple threads simultaneously. When a variable is declared as volatile, the Java Virtual Machine ensures that all threads see the same value of the variable at any given time.

This keyword is mainly used to prevent race conditions that may arise when two or more threads access a shared variable at the same time. When a variable is marked as volatile, its value is always read from main memory and not from a thread's local cache. Similarly, any change in the value of a volatile variable is immediately visible to all threads accessing it.

The volatile keyword is also used for memory consistency. When a variable is declared as volatile, all writes to the variable are guaranteed to be visible to other threads before any subsequent reads from the same variable.