Class ZgcGenerationalModeExamples

java.lang.Object

net.jrodolfo.java_evolution.java23.zgc_generational_mode.ZgcGenerationalModeExamples

public class ZgcGenerationalModeExamples
extends Object

Demonstrates the Java 23 ZGC generational-mode runtime boundary.

Java 23 made generational mode the default for ZGC. This example launches child JVMs to verify the executable part that is portable on ZGC-capable builds: ZGC can be selected, -XX:+PrintFlagsFinal reports UseZGC = true, and GC initialization logs mention young and old generation workers.

The example does not benchmark garbage collection. Throughput, pause time, heap footprint, and CPU behavior require real workloads and measurement.

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static final record	ZgcGenerationalModeExamples.ProcessResult	Captures a child process result.
static final record	ZgcGenerationalModeExamples.VmFlagState	A JVM flag state reported by -XX:+PrintFlagsFinal.

Constructor Summary

Constructors

Constructor	Description
ZgcGenerationalModeExamples()

Method Summary

Modifier and Type	Method	Description
String	benchmarkBoundary()	Explains the boundary of the executable example.
String	generationalObservation()	Explains the generational observation behind the Java 23 default change.
ZgcGenerationalModeExamples.ProcessResult	oldGenerationalSwitchStatus()	Captures the status of the old ZGenerational switch in Java 24+.
boolean	zgcAvailable()	Checks whether the current JVM build supports ZGC.
ZgcGenerationalModeExamples.VmFlagState	zgcFlagState()	Reads the child JVM flag state after selecting ZGC.
ZgcGenerationalModeExamples.ProcessResult	zgcInitializationLog()	Captures ZGC initialization logs.

Methods inherited from class Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Details

ZgcGenerationalModeExamples

public ZgcGenerationalModeExamples()

Method Details

zgcAvailable

public boolean zgcAvailable()
                     throws IOException,
InterruptedException

Checks whether the current JVM build supports ZGC.

Returns:

true when a child JVM starts with -XX:+UseZGC

Throws:

IOException - if the child JVM cannot be started

InterruptedException - if interrupted while waiting for the child JVM

zgcFlagState

public ZgcGenerationalModeExamples.VmFlagState zgcFlagState()
                                                     throws IOException,
InterruptedException

Reads the child JVM flag state after selecting ZGC.

Returns:

the reported UseZGC flag state

Throws:

IOException - if the child JVM cannot be started

InterruptedException - if interrupted while waiting for the child JVM

zgcInitializationLog

public ZgcGenerationalModeExamples.ProcessResult zgcInitializationLog()
                                                               throws IOException,
InterruptedException

Captures ZGC initialization logs.

Returns:

child JVM result containing gc+init output

Throws:

IOException - if the child JVM cannot be started

InterruptedException - if interrupted while waiting for the child JVM

oldGenerationalSwitchStatus

public ZgcGenerationalModeExamples.ProcessResult oldGenerationalSwitchStatus()
                                                                      throws IOException,
InterruptedException

Captures the status of the old ZGenerational switch in Java 24+.

Returns:

child JVM result showing whether the old switch is still meaningful

Throws:

IOException - if the child JVM cannot be started

InterruptedException - if interrupted while waiting for the child JVM

generationalObservation

public String generationalObservation()

Explains the generational observation behind the Java 23 default change.

Returns:

a short explanation

benchmarkBoundary

public String benchmarkBoundary()

Explains the boundary of the executable example.

Returns:

a short boundary explanation