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| Code Block | ||
|---|---|---|
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class InventoryManager {
private final AtomicInteger itemsInInventory = new AtomicInteger(100);
public final void returnItem() {
int old;
do while (true) {
int old = itemsInInventory.get();
if (old == Integer.MAX_VALUE) {
throw new IllegalStateException("Out of bounds");
}
int next = old + 1; // Decrement
} whileif (!itemsInInventory.compareAndSet(old, itemsInInventory.incrementAndGet()));
} next)) {
break;
}
} // end while
} // end removeItem()
}
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| Wiki Markup |
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The {{compareAndSet()}} method takes two arguments, the expected value of a variable when the method is invoked and the updated value. This compliant solution uses this method to atomically set the value of {{itemsInInventory}} to the updated value if and only if the current value equals the expected value \[[API 06|AA. Java References#API 06]\]. The while loop ensures that the {{removeItem()}} method succeeds in decrementing the most recent value of {{itemsInInventory}} as long as the inventory count is greater than {{MIN_INVENTORY}}. Refer to [CON01-J. Ensure that compound operations on shared variables are atomic] for more details. |
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