Thread safety in Java refers to the process of making a program safe to use in a multithreaded environment. When multiple threads are working on the same data, and the value of the data is changing, that scenario is not thread-safe and can lead to inconsistent results. Thread safety is important because Java provides multi-threaded environment support using Java Threads, and multiple threads created from the same object share object variables, which can lead to data inconsistency when the threads are used to read and update the shared data.
To achieve thread safety in Java, there are different ways through which we can make our program thread-safe. Here are some of the ways:
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Synchronization: This is the tool using which we can achieve thread-safety. JVM guarantees that synchronized code will be executed by only one thread at a time. The Java keyword synchronized is used to create synchronized code and internally it uses locks on Object or Class to make sure only one thread is executing the synchronized code. synchronized(this) will lock the Object before entering into the synchronized block.
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Immutable objects: Immutable objects are by default thread-safe because their state cannot be modified once created. Since String is immutable in Java, it’s inherently thread-safe. Read-only or final variables in Java are also thread-safe.
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Locking: Locking is another way of achieving thread-safety in Java. When variables are shared between threads, we can use locks to ensure that only one thread can access the variable at a time.
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Atomic variables: Using an atomic variable is another way to achieve thread-safety in Java. When variables are shared between threads, we can use atomic variables to ensure that only one thread can access the variable at a time.
Thread-safe collections in Java can be applicable in situations where multiple threads are accessing and modifying a shared collection simultaneously. The use of thread-safe collections can help prevent race conditions, where two or more threads try to access or modify the same data at the same time, leading to unpredictable or incorrect results. Some examples of thread-safe collections in Java include java.util.concurrent.ConcurrentHashMap, java.util.concurrent.CopyOnWriteArrayList, and java.util.concurrent.BlockingQueue.
