Lära Thread Safety and Shared Data | Concurrency Basics in Kotlin

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Understanding thread safety is crucial when writing concurrent programs in Kotlin. Thread safety means that a piece of code or a data structure behaves correctly when accessed from multiple threads at the same time. In concurrent programming, multiple threads often need to read from or write to the same variables or objects. If these accesses are not properly managed, unpredictable behavior and difficult-to-reproduce bugs can occur. This is especially important in Android and backend development, where background operations frequently interact with shared data. Common pitfalls include modifying shared variables without proper coordination, leading to inconsistent or incorrect results. Such problems are often subtle and can cause applications to crash or produce incorrect outputs, making them challenging to debug and fix.

Main.kt


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package com.example

fun main() {
    var counter = 0

    val thread1 = Thread {
        repeat(1000) {
            counter++
        }
    }

    val thread2 = Thread {
        repeat(1000) {
            counter++
        }
    }

    thread1.start()
    thread2.start()
    thread1.join()
    thread2.join()

    println("Final counter value: $counter")
}

In this example, two threads both increment the same counter variable 1,000 times. You might expect the final value to always be 2,000, but in practice, the result is often less than that. This issue is known as a race condition. A race condition happens when the outcome of a program depends on the unpredictable timing of threads accessing shared data. Here, both threads read, increment, and write back to counter without coordination. If both threads read the same value before either writes back, one increment is lost. To avoid such issues, you can use synchronization mechanisms like synchronized blocks, atomic variables, or design your program to use immutable data structures. These strategies ensure that only one thread can modify the shared data at a time, or that shared data is never changed after creation, preventing unpredictable results.

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