com.datastax.util.concurrency.Immutable Maven / Gradle / Ivy
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package com.datastax.util.concurrency;
import java.lang.annotation.Documented;
import java.lang.annotation.Retention;
import java.lang.annotation.Target;
import static java.lang.annotation.ElementType.TYPE;
import static java.lang.annotation.RetentionPolicy.RUNTIME;
/**
* The presence of this annotation indicates that the author believes the class to be immutable and hence inherently
* thread-safe. An immutable class is one where the state of an instance cannot be seen to change. As a result
*
* - All public fields must be {@code final}
* - All public final reference fields are either {@code null} or refer to other immutable objects
* - Constructors and methods do not publish references to any potentially mutable internal state.
*
* Performance optimization may mean that instances of an immutable class may have mutable internal state. The
* critical point is that callers cannot tell the difference. For example {@link String} is an immutable class, despite
* having an internal int that is non-final but used as a cache for {@link String#hashCode()}.
*
* Immutable objects are inherently thread-safe; they may be passed between threads or published without
* synchronization.
*/
@Documented
@Target(TYPE)
@Retention(RUNTIME)
public @interface Immutable {
}