This class provides services needed to instrument Java programming language code. Instrumentation is the addition of byte-codes to methods for the purpose of gathering data to be utilized by tools. Since the changes are purely additive, these tools do not modify application state or behavior. Examples of such benign tools include monitoring agents, profilers, coverage analyzers, and event loggers.
There are two ways to obtain an instance of the
Instrumentation interface:
When a JVM is launched in a way that indicates an agent
class. In that case an Instrumentation instance
is passed to the premain method of the agent class.
When a JVM provides a mechanism to start agents sometime
after the JVM is launched. In that case an Instrumentation
instance is passed to the agentmain method of the
agent code.
These mechanisms are described in the package specification.
Once an agent acquires an Instrumentation instance,
the agent may call methods on the instance at any time.