Jvm (OpenHFT/Chronicle Core 2.27ea0 API)

java.lang.Object
- net.openhft.chronicle.core.Jvm

```
public final class Jvm
extends Object
```
Utility class to access information in the JVM.

Nested Class Summary

Nested Classes
Modifier and Type Class and Description

static interface Jvm.SignalHandler

Nested Classes
Modifier and Type	Class and Description
`static interface`	`Jvm.SignalHandler`

Field Summary

Fields
Modifier and Type Field and Description

static String JAVA_CLASS_PATH

static String SYSTEM_PROPERTIES

Fields
Modifier and Type	Field and Description
`static String`	`JAVA_CLASS_PATH`
`static String`	`SYSTEM_PROPERTIES`

Method Summary

All Methods Static Methods Concrete Methods
Modifier and Type	Method and Description
`static long`	`address(@NotNull ByteBuffer byteBuffer)` Returns the native address of the provided `byteBuffer`.
`static void`	`addSignalHandler(Jvm.SignalHandler signalHandler)` Adds the provided `signalHandler` to an internal chain of handlers that will be invoked upon detecting system signals (e.g.
`static void`	`addToClassPath(@NotNull Class<?> clazz)` Ensures that all the jars and other resources are added to the class path of the classloader associated by the provided `clazz`.
`static boolean`	`areOptionalSafepointsEnabled()`
`static int`	`arrayByteBaseOffset()` Returns the array byte base offset used by this JVM.
`static void`	`busyWaitMicros(long durationUs)` Pause in a busy loop for the provided `durationUs` microseconds.
`static void`	`busyWaitUntil(long waitUntilNs)` Pauses the current thread in a busy loop until the provided `waitUntilNs` time is reached.
`static @NotNull ClassMetrics`	`classMetrics(Class<?> clazz)` Acquires and returns the ClassMetrics for the provided `clazz`.
`static int`	`compileThreshold()` Returns the compile threshold for the JVM or else an estimate thereof (e.g.
`static long`	`currentThreadId()` Retrieves the unique identifier of the current thread.
`static @NotNull ExceptionHandler`	`debug()` Returns an ExceptionHandler for debug messages, this prints as System.out or DEBUG level logging.
`static void`	`disableDebugHandler()`
`static void`	`disablePerfHandler()`
`static void`	`disableWarnHandler()`
`static void`	`doNotCloseOnInterrupt(Class<?> clazz, FileChannel fc)` Employs a best-effort of preventing the provided `fc` from being automatically closed whenever the current thread gets interrupted.
`static boolean`	`dontChain(Class<?> tClass)`
`static void`	`dumpException(@NotNull Map<ExceptionKey,Integer> exceptions)`
`static @NotNull ExceptionHandler`	`error()` Returns an ExceptionHandler for errors, this prints as System.err or ERROR level logging.
`static long`	`fieldOffset(Class<?> clazz, String fieldName)`
`static <A extends Annotation> A`	`findAnnotation(AnnotatedElement annotatedElement, Class<A> annotationType)` Retrieve an annotation of the specified `annotationType` that is present on the given `annotatedElement`, including considering nested annotations and method inheritance.
`static boolean`	`getBoolean(String systemPropertyKey)` Returns if a System Property with the provided `systemPropertyKey` either exists, is set to "yes" or is set to "true".
`static boolean`	`getBoolean(String systemPropertyKey, boolean defaultValue)` Returns if a System Property with the provided `systemPropertyKey` either exists, is set to "yes" or is set to "true" or, if it does not exist, returns the provided `defaultValue`.
`static String`	`getCpuClass()`
`static double`	`getDouble(String systemPropertyKey, double defaultValue)` Returns the System Property associated with the provided `systemPropertyKey` parsed as a `double` or, if no such parsable System Property exists, returns the provided `defaultValue`.
`static @NotNull Field`	`getField(@NotNull Class<?> clazz, @NotNull String fieldName)` Returns the Field for the provided `clazz` and the provided `fieldName` or throws an Exception if no such Field exists.
`static @Nullable Field`	`getFieldOrNull(@NotNull Class<?> clazz, @NotNull String fieldName)` Returns the Field for the provided `clazz` and the provided `fieldName` or `null` if no such Field exists.
`static Integer`	`getInteger(String systemPropertyKey, Integer defVal)` Guarantees that Jvm class is initialized before property is read.
`static Long`	`getLong(String systemPropertyKey, Long defVal)` Guarantees that Jvm class is initialized before property is read.
`static @NotNull Method`	`getMethod(@NotNull Class<?> clazz, @NotNull String methodName, Class<?>... argTypes)` Returns the Method for the provided `clazz`, `methodName` and `argTypes` or throws an Exception.
`static String`	`getPackageName(Class clazz)` Returns the package name of the specified class.
`static int`	`getProcessId()` Returns the current process id.
`static String`	`getProperty(String systemPropertyKey)` Guarantees that Jvm class is initialized before property is read.
`static String`	`getProperty(String systemPropertyKey, String defaultValue)` Guarantees that Jvm class is initialized before property is read.
`static long`	`getSize(String property, long defaultValue)` Uses Jvm.parseSize to parse a system property or returns defaultValue if not present, empty or unparseable.
`static <V> V`	`getValue(@NotNull Object target, @NotNull String fieldName)` Returns the value of the provided `fieldName` extracted from the provided `target`.
`static boolean`	`hasException(@NotNull Map<ExceptionKey,Integer> exceptions)`
`static void`	`init()`
`static boolean`	`is64bit()` Returns if the JVM runs in 64 bit mode.
`static boolean`	`isArm()` Returns if the JVM runs on a CPU using the ARM architecture.
`static boolean`	`isAssertEnabled()` Was assertion enabled for the Jvm class when it was initialised.
`static boolean`	`isAzulZing()`
`static boolean`	`isAzulZulu()`
`static boolean`	`isCodeCoverage()` Returns if the JVM is running in code coverage mode.
`static boolean`	`isDebug()` Returns if the JVM is running in debug mode.
`static boolean`	`isDebugEnabled(Class<?> aClass)`
`static boolean`	`isFlightRecorder()` Returns if the JVM is running in flight recorder mode.
`static boolean`	`isJava12Plus()`
`static boolean`	`isJava14Plus()`
`static boolean`	`isJava15Plus()`
`static boolean`	`isJava19Plus()`
`static boolean`	`isJava20Plus()`
`static boolean`	`isJava21Plus()`
`static boolean`	`isJava9Plus()`
`static boolean`	`isLambdaClass(Class<?> clazz)` Checks if the given class represents a lambda expression.
`static boolean`	`isMacArm()` Returns if the JVM runs on a CPU using a Mac ARM architecture.
`static boolean`	`isPerfEnabled(Class<?> aClass)`
`static boolean`	`isProcessAlive(long pid)` Returns if a process with the provided `pid` process id is alive.
`static boolean`	`isResourceTracing()` Returns if certain chronicle resources (such as memory regions) are traced.
`static String`	`lockWithStack(@NotNull ReentrantLock lock)` Log the stack trace of the thread holding a lock.
`static int`	`majorVersion()`
`static long`	`maxDirectMemory()` Returns the maximum direct memory in bytes that can ever be allocated or 0 if the value cannot be determined.
`static void`	`nanoPause()` Pause in a busy loop for a very short time.
`static void`	`park()` park the current thread, and stay parked
`static long`	`parseSize(@NotNull String value)` Parse a string as a decimal memory size with an optional scale.
`static void`	`pause(long durationMs)` Silently pause for the provided `durationMs` milliseconds.
`static @NotNull ExceptionHandler`	`perf()` Returns an ExceptionHandler for performance messages, this prints as System.out or INFO level logging.
`static @NotNull Map<ExceptionKey,Integer>`	`recordExceptions()`
`static @NotNull Map<ExceptionKey,Integer>`	`recordExceptions(boolean debug)`
`static @NotNull Map<ExceptionKey,Integer>`	`recordExceptions(boolean debug, boolean exceptionsOnly)`
`static @NotNull Map<ExceptionKey,Integer>`	`recordExceptions(boolean debug, boolean exceptionsOnly, boolean logToSlf4j)`
`static void`	`reportUnoptimised()`
`static void`	`resetExceptionHandlers()`
`static <T extends Throwable> @NotNull RuntimeException`	`rethrow(Throwable throwable)` Cast any Throwable (e.g.
`static void`	`safepoint()` Inserts a low-cost Java safe-point in the code path if -Djvm.safepoint.enabled
`static void`	`setAccessible(@NotNull AccessibleObject accessibleObject)` Set the accessible flag for the provided `accessibleObject` indicating that the reflected object should suppress Java language access checking when it is used.
`static void`	`setDebugExceptionHandler(ExceptionHandler exceptionHandler)`
`static void`	`setErrorExceptionHandler(ExceptionHandler exceptionHandler)`
`static void`	`setExceptionHandlers(@Nullable ExceptionHandler error, @Nullable ExceptionHandler warn, @Nullable ExceptionHandler debug)`
`static void`	`setExceptionHandlers(@Nullable ExceptionHandler error, @Nullable ExceptionHandler warn, @Nullable ExceptionHandler debug, @Nullable ExceptionHandler perf)`
`static void`	`setPerfExceptionHandler(ExceptionHandler exceptionHandler)`
`static void`	`setResourceTracing(boolean resourceTracing)` Sets the state of resource tracing.
`static void`	`setThreadLocalExceptionHandlers(@Nullable ExceptionHandler error, @Nullable ExceptionHandler warn, @Nullable ExceptionHandler debug)`
`static void`	`setThreadLocalExceptionHandlers(@Nullable ExceptionHandler error, @Nullable ExceptionHandler warn, @Nullable ExceptionHandler debug, @Nullable ExceptionHandler perf)`
`static void`	`setWarnExceptionHandler(ExceptionHandler exceptionHandler)`
`static boolean`	`stackTraceEndsWith(String endsWith, int maxDepth)` Returns if there is a class name that ends with the provided `endsWith` string when examining the current stack trace of depth at most up to the provided `maxDepth`.
`static @NotNull ExceptionHandler`	`startup()` Returns an ExceptionHandler for startup messages, this prints as System.out or INFO level logging.
`static boolean`	`supportThread()`
`static int`	`trimLast(int first, @NotNull StackTraceElement[] stes)`
`static void`	`trimStackTrace(@NotNull StringBuilder stringBuilder, StackTraceElement... stackTraceElements)` Append the provided `StackTraceElements` to the provided `stringBuilder` trimming some internal methods.
`static <T> Class<T>`	`uncheckedCast(Class<?> o)` Performs an unchecked cast of a `Class` object to `Class<T>`.
`static <T> T`	`uncheckedCast(Object o)` Performs an unchecked cast of an object to the target type `T`.
`static <T> T[]`	`uncheckedCast(Object[] o)` Performs an unchecked cast of an array of objects to an array of the target type `T[]`.
`static long`	`usedDirectMemory()` Returns the accumulated amount of memory in bytes used by direct ByteBuffers or 0 if the value cannot be determined.
`static long`	`usedNativeMemory()` Returns the accumulated amount of memory used in bytes by UnsafeMemory.allocate().
`static @NotNull String`	`userHome()` Returns the user's home directory (e.g.
`static @NotNull ExceptionHandler`	`warn()` Returns an ExceptionHandler for warnings, this prints as System.out or WARN level logging.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail
- JAVA_CLASS_PATH
```
public static final String JAVA_CLASS_PATH
```
  See Also:
  
  Constant Field Values
- SYSTEM_PROPERTIES
```
public static final String SYSTEM_PROPERTIES
```
  See Also:
  
  Constant Field Values

Method Detail

reportUnoptimised

public static void reportUnoptimised()

init
```
public static void init()
```

compileThreshold
```
public static int compileThreshold()
```
Returns the compile threshold for the JVM or else an estimate thereof (e.g. 10_000).
The compile threshold can be explicitly set using the command line parameter "-XX:CompileThreshold="

Returns:

the compile threshold for the JVM or else an estimate thereof (e.g. 10_000)

majorVersion
```
public static int majorVersion()
```
Returns:

the major Java version (e.g. 8, 11 or 17)

isJava9Plus
```
public static boolean isJava9Plus()
```
Returns:

if the major Java version is 9 or higher

isJava12Plus
```
public static boolean isJava12Plus()
```
Returns:

if the major Java version is 12 or higher

isJava14Plus
```
public static boolean isJava14Plus()
```
Returns:

if the major Java version is 14 or higher

isJava15Plus
```
public static boolean isJava15Plus()
```
Returns:

if the major Java version is 15 or higher

isJava19Plus
```
public static boolean isJava19Plus()
```
Returns:

if the major Java version is 19 or higher

isJava20Plus
```
public static boolean isJava20Plus()
```
Returns:

if the major Java version is 20 or higher

isJava21Plus
```
public static boolean isJava21Plus()
```
Returns:

if the major Java version is 21 or higher

getProcessId
```
public static int getProcessId()
```
Returns the current process id.

Returns:

the current process id or, if the process id cannot be determined, 1 is used.

rethrow
```
@NotNull
public static <T extends Throwable> @NotNull RuntimeException rethrow(Throwable throwable)
                                                                        throws T extends Throwable
```
Cast any Throwable (e.g. a checked exception) to a RuntimeException.

Type Parameters:

T - the type of the Throwable

Parameters:

throwable - to cast

Returns:

this method will never return a Throwable instance, it will just throw it.

Throws:

T - the throwable as an unchecked throwable

T extends Throwable

trimStackTrace

public static void trimStackTrace(@NotNull
                                  @NotNull StringBuilder stringBuilder,
                                  @NotNull
                                  StackTraceElement... stackTraceElements)

Append the provided StackTraceElements to the provided stringBuilder trimming some internal methods.

Parameters:: stringBuilder - to append to; stackTraceElements - stack trace elements

trimLast

public static int trimLast(int first,
                           @NotNull
                           @NotNull StackTraceElement[] stes)

isDebug
```
public static boolean isDebug()
```
Returns if the JVM is running in debug mode.

Returns:

if the JVM is running in debug mode

isFlightRecorder
```
public static boolean isFlightRecorder()
```
Returns if the JVM is running in flight recorder mode.

Returns:

if the JVM is running in flight recorder mode

isCodeCoverage
```
public static boolean isCodeCoverage()
```
Returns if the JVM is running in code coverage mode.

Returns:

if the JVM is running in code coverage mode

pause
```
public static void pause(long durationMs)
```
Silently pause for the provided durationMs milliseconds.
If the provided durationMs is positive, then the current thread sleeps.
If the provided durationMs is zero, then the current thread yields.

Parameters:

durationMs - to sleep for.

nanoPause
```
public static void nanoPause()
```
Pause in a busy loop for a very short time.

busyWaitMicros
```
public static void busyWaitMicros(long durationUs)
```
Pause in a busy loop for the provided durationUs microseconds.
This method is designed to be used when the time to be waited is very small, typically under a millisecond (@{code durationUs < 1_000}).

Parameters:

durationUs - Time in durationUs

busyWaitUntil
```
public static void busyWaitUntil(long waitUntilNs)
```
Pauses the current thread in a busy loop until the provided waitUntilNs time is reached.
This method is designed to be used when the time to be waited is very small, typically under a millisecond (@{code durationNs < 1_000_000}).

Parameters:

waitUntilNs - nanosecond precision counter value to await.

getField

@NotNull
public static @NotNull Field getField(@NotNull
                                               @NotNull Class<?> clazz,
                                               @NotNull
                                               @NotNull String fieldName)

Returns the Field for the provided clazz and the provided fieldName or throws an Exception if no such Field exists.

Parameters:: clazz - to get the field for; fieldName - of the field
Returns:: the Field.
Throws:: AssertionError - if no such Field exists

getFieldOrNull

@Nullable
public static @Nullable Field getFieldOrNull(@NotNull
                                                       @NotNull Class<?> clazz,
                                                       @NotNull
                                                       @NotNull String fieldName)

Returns the Field for the provided clazz and the provided fieldName or null if no such Field exists.

Parameters:: clazz - to get the field for; fieldName - of the field
Returns:: the Field.
Throws:: AssertionError - if no such Field exists

getMethod

@NotNull
public static @NotNull Method getMethod(@NotNull
                                                 @NotNull Class<?> clazz,
                                                 @NotNull
                                                 @NotNull String methodName,
                                                 Class<?>... argTypes)

Returns the Method for the provided clazz, methodName and argTypes or throws an Exception.

if it exists or throws AssertionError.

Default methods are not detected unless the class explicitly overrides it

Parameters:: clazz - class; methodName - methodName; argTypes - argument types
Returns:: method
Throws:: AssertionError - if no such Method exists

setAccessible
```
public static void setAccessible(@NotNull
                                 @NotNull AccessibleObject accessibleObject)
```
Set the accessible flag for the provided accessibleObject indicating that the reflected object should suppress Java language access checking when it is used.
The setting of the accessible flag might be subject to security manager approval.

Parameters:

accessibleObject - to modify

Throws:

SecurityException - – if the request is denied.

See Also:

SecurityManager.checkPermission(java.security.Permission), RuntimePermission

getValue
```
@Nullable
public static <V> V getValue(@NotNull
                                       @NotNull Object target,
                                       @NotNull
                                       @NotNull String fieldName)
```
Returns the value of the provided fieldName extracted from the provided target.
The provided fieldName can denote fields of arbitrary depth (e.g. foo.bar.baz, whereby the foo value will be extracted from the provided target and then the bar value will be extracted from the foo value and so on).

Type Parameters:

V - return type

Parameters:

target - used for extraction

fieldName - denoting the field(s) to extract

Returns:

the value of the provided fieldName extracted from the provided target

lockWithStack
```
public static String lockWithStack(@NotNull
                                   @NotNull ReentrantLock lock)
```
Log the stack trace of the thread holding a lock.

Parameters:

lock - to log

Returns:

the lock.toString plus a stack trace.

fieldOffset
```
public static long fieldOffset(Class<?> clazz,
                               String fieldName)
```
Parameters:

clazz - the class for which you want to get field from [ it won't see inherited fields ]

fieldName - the name of the field

Returns:

the offset

usedDirectMemory
```
public static long usedDirectMemory()
```
Returns the accumulated amount of memory in bytes used by direct ByteBuffers or 0 if the value cannot be determined.
(i.e. ever allocated via ByteBuffer.allocateDirect())

Returns:

the accumulated amount of memory in bytes used by direct ByteBuffers or 0 if the value cannot be determined

usedNativeMemory
```
public static long usedNativeMemory()
```
Returns the accumulated amount of memory used in bytes by UnsafeMemory.allocate().

Returns:

the accumulated amount of memory used in bytes by UnsafeMemory.allocate()

maxDirectMemory
```
public static long maxDirectMemory()
```
Returns the maximum direct memory in bytes that can ever be allocated or 0 if the value cannot be determined. (i.e. ever allocated via ByteBuffer.allocateDirect())

Returns:

the maximum direct memory in bytes that can ever be allocated or 0 if the value cannot be determined

is64bit
```
public static boolean is64bit()
```
Returns if the JVM runs in 64 bit mode.

Returns:

if the JVM runs in 64 bit mode

resetExceptionHandlers

public static void resetExceptionHandlers()

setErrorExceptionHandler

public static void setErrorExceptionHandler(ExceptionHandler exceptionHandler)

setWarnExceptionHandler

public static void setWarnExceptionHandler(ExceptionHandler exceptionHandler)

setDebugExceptionHandler

public static void setDebugExceptionHandler(ExceptionHandler exceptionHandler)

setPerfExceptionHandler

public static void setPerfExceptionHandler(ExceptionHandler exceptionHandler)

disableDebugHandler

public static void disableDebugHandler()

disablePerfHandler

public static void disablePerfHandler()

disableWarnHandler

public static void disableWarnHandler()

recordExceptions

@NotNull
public static @NotNull Map<ExceptionKey,Integer> recordExceptions()

recordExceptions

@NotNull
public static @NotNull Map<ExceptionKey,Integer> recordExceptions(boolean debug)

recordExceptions

@NotNull
public static @NotNull Map<ExceptionKey,Integer> recordExceptions(boolean debug,
                                                                           boolean exceptionsOnly)

recordExceptions

@NotNull
public static @NotNull Map<ExceptionKey,Integer> recordExceptions(boolean debug,
                                                                           boolean exceptionsOnly,
                                                                           boolean logToSlf4j)

hasException

public static boolean hasException(@NotNull
                                   @NotNull Map<ExceptionKey,Integer> exceptions)

setExceptionHandlers

public static void setExceptionHandlers(@Nullable
                                        @Nullable ExceptionHandler error,
                                        @Nullable
                                        @Nullable ExceptionHandler warn,
                                        @Nullable
                                        @Nullable ExceptionHandler debug)

setExceptionHandlers

public static void setExceptionHandlers(@Nullable
                                        @Nullable ExceptionHandler error,
                                        @Nullable
                                        @Nullable ExceptionHandler warn,
                                        @Nullable
                                        @Nullable ExceptionHandler debug,
                                        @Nullable
                                        @Nullable ExceptionHandler perf)

setThreadLocalExceptionHandlers

public static void setThreadLocalExceptionHandlers(@Nullable
                                                   @Nullable ExceptionHandler error,
                                                   @Nullable
                                                   @Nullable ExceptionHandler warn,
                                                   @Nullable
                                                   @Nullable ExceptionHandler debug)

setThreadLocalExceptionHandlers

public static void setThreadLocalExceptionHandlers(@Nullable
                                                   @Nullable ExceptionHandler error,
                                                   @Nullable
                                                   @Nullable ExceptionHandler warn,
                                                   @Nullable
                                                   @Nullable ExceptionHandler debug,
                                                   @Nullable
                                                   @Nullable ExceptionHandler perf)

error
```
@NotNull
public static @NotNull ExceptionHandler error()
```
Returns an ExceptionHandler for errors, this prints as System.err or ERROR level logging. In tests these messages are usually captured and checked that the error expected and only those expected are produced.

Returns:

the ERROR exception handler

warn
```
@NotNull
public static @NotNull ExceptionHandler warn()
```
Returns an ExceptionHandler for warnings, this prints as System.out or WARN level logging. In tests these messages are usually captured and checked that the warning expected and only those expected are produced.

Returns:

the WARN exception handler

startup
```
@NotNull
public static @NotNull ExceptionHandler startup()
```
Returns an ExceptionHandler for startup messages, this prints as System.out or INFO level logging. In tests these messages are generally not captured for checking.

Returns:

the STARTUP exception handler

perf
```
@NotNull
public static @NotNull ExceptionHandler perf()
```
Returns an ExceptionHandler for performance messages, this prints as System.out or INFO level logging. In tests these messages are generally not captured for checking, but a few tests may check performance metrics are reported.

Returns:

the PERF exception handler

debug
```
@NotNull
public static @NotNull ExceptionHandler debug()
```
Returns an ExceptionHandler for debug messages, this prints as System.out or DEBUG level logging. In tests these messages are generally not captured for checking.

Returns:

the DEBUG exception handler

dumpException

public static void dumpException(@NotNull
                                 @NotNull Map<ExceptionKey,Integer> exceptions)

isDebugEnabled

public static boolean isDebugEnabled(Class<?> aClass)

isPerfEnabled

public static boolean isPerfEnabled(Class<?> aClass)

addSignalHandler
```
public static void addSignalHandler(Jvm.SignalHandler signalHandler)
```
Adds the provided signalHandler to an internal chain of handlers that will be invoked upon detecting system signals (e.g. HUP, INT, TERM).
Not all signals are available on all operating systems.

Parameters:

signalHandler - to call on a signal

safepoint
```
public static void safepoint()
```
Inserts a low-cost Java safe-point in the code path if -Djvm.safepoint.enabled

areOptionalSafepointsEnabled

public static boolean areOptionalSafepointsEnabled()

stackTraceEndsWith
```
public static boolean stackTraceEndsWith(String endsWith,
                                         int maxDepth)
```
Returns if there is a class name that ends with the provided endsWith string when examining the current stack trace of depth at most up to the provided maxDepth.

Parameters:

endsWith - to test against the current stack trace

maxDepth - to examine

Returns:

if there is a class name that ends with the provided endsWith string when examining the current stack trace of depth at most up to the provided maxDepth

isArm
```
public static boolean isArm()
```
Returns if the JVM runs on a CPU using the ARM architecture.

Returns:

if the JVM runs on a CPU using the ARM architecture

isMacArm
```
public static boolean isMacArm()
```
Returns if the JVM runs on a CPU using a Mac ARM architecture.

Returns:

if the JVM runs on a CPU using the Mac ARM architecture e.g. Apple M1.

classMetrics
```
@NotNull
public static @NotNull ClassMetrics classMetrics(Class<?> clazz)
                                                   throws IllegalArgumentException
```
Acquires and returns the ClassMetrics for the provided clazz.

Parameters:

clazz - for which ClassMetrics shall be acquired

Returns:

the ClassMetrics for the provided clazz

Throws:

IllegalArgumentException - if no ClassMetrics can be acquired

See Also:

ClassMetrics

userHome
```
@NotNull
public static @NotNull String userHome()
```
Returns the user's home directory (e.g. "/home/alice") or "." if the user's home director cannot be determined.

Returns:

the user's home directory (e.g. "/home/alice") or "." if the user's home director cannot be determined

dontChain

public static boolean dontChain(Class<?> tClass)

isResourceTracing
```
public static boolean isResourceTracing()
```
Returns if certain chronicle resources (such as memory regions) are traced.
Tracing resources incurs slightly less performance but provides a means of detecting proper release of resources.

Returns:

true if specific chronicle resources are traced, false otherwise.

setResourceTracing
```
public static void setResourceTracing(boolean resourceTracing)
```
Sets the state of resource tracing. This is especially useful for testing scenarios.
Note: Enabling resource tracing can exert significant pressure on the garbage collector during stress tests.

Parameters:

resourceTracing - true to enable resource tracing, false to disable.

getProperty
```
public static String getProperty(String systemPropertyKey)
```
Guarantees that Jvm class is initialized before property is read.

See Also:

System.getProperty(String)

getProperty

public static String getProperty(String systemPropertyKey,
                                 String defaultValue)

Guarantees that Jvm class is initialized before property is read.

See Also:: System.getProperty(String, String)

getLong

public static Long getLong(String systemPropertyKey,
                           Long defVal)

Guarantees that Jvm class is initialized before property is read.

See Also:: Long.getLong(String, Long)

getInteger

public static Integer getInteger(String systemPropertyKey,
                                 Integer defVal)

Guarantees that Jvm class is initialized before property is read.

See Also:: Integer.getInteger(String, Integer)

getBoolean
```
public static boolean getBoolean(String systemPropertyKey)
```
Returns if a System Property with the provided systemPropertyKey either exists, is set to "yes" or is set to "true".
This provides a more permissive boolean System systemPropertyKey flag where -Dflag -Dflag=true -Dflag=yes are all accepted.
Guarantees that Jvm class is initialized before property is read.

Parameters:

systemPropertyKey - name to lookup

Returns:

if a System Property with the provided systemPropertyKey either exists, is set to "yes" or is set to "true"

getBoolean
```
public static boolean getBoolean(String systemPropertyKey,
                                 boolean defaultValue)
```
Returns if a System Property with the provided systemPropertyKey either exists, is set to "yes" or is set to "true" or, if it does not exist, returns the provided defaultValue.
This provides a more permissive boolean System systemPropertyKey flag where -Dflag -Dflag=true -Dflag=yes are all accepted.
Guarantees that Jvm class is initialized before property is read.

Parameters:

systemPropertyKey - name to lookup

defaultValue - value to be used if unknown

Returns:

if a System Property with the provided systemPropertyKey either exists, is set to "yes" or is set to "true" or, if it does not exist, returns the provided defaultValue.

parseSize

public static long parseSize(@NotNull
                             @NotNull String value)
                      throws IllegalArgumentException

Parse a string as a decimal memory size with an optional scale. K/k = * 2¹⁰, M/m = 2²⁰, G/g = 2¹⁰, T/t = 2⁴⁰

trailing B/b/iB/ib are ignored.

This table illustrates examples of various string inputs representing memory sizes and their corresponding parsed outputs in bytes. It demonstrates how strings with different suffixes and formats are converted to their respective byte equivalents using factors like kilobytes (KB), megabytes (MB), gigabytes (GB), and terabytes (TB), where these units are powers of 2.
100	100 bytes
100b	100 bytes
0.5kb	512 bytes
0.125MB	128 KiB
2M	2 MiB
0.75GiB	768 MiB
0.001TiB	1.024 GiB

Parameters:: value - size to parse
Returns:: the size
Throws:: IllegalArgumentException - if the string could not be parsed

getSize
```
public static long getSize(String property,
                           long defaultValue)
```
Uses Jvm.parseSize to parse a system property or returns defaultValue if not present, empty or unparseable.

Parameters:

property - to look up

defaultValue - to use otherwise

Returns:

the size in bytes as a long

address
```
public static long address(@NotNull
                           @NotNull ByteBuffer byteBuffer)
```
Returns the native address of the provided byteBuffer.
Use with caution!. Native address should always be carefully guarded to prevent unspecified results or even JVM crashes.

Parameters:

byteBuffer - from which to extract the native address

Returns:

the native address of the provided byteBuffer

arrayByteBaseOffset
```
public static int arrayByteBaseOffset()
```
Returns the array byte base offset used by this JVM.
The value is the number of bytes that precedes the actual memory layout of a byte[] array in a java array object.
Use with caution!. Native address should always be carefully guarded to prevent unspecified results or even JVM crashes.

Returns:

the array byte base offset used by this JVM

doNotCloseOnInterrupt
```
public static void doNotCloseOnInterrupt(Class<?> clazz,
                                         FileChannel fc)
```
Employs a best-effort of preventing the provided fc from being automatically closed whenever the current thread gets interrupted.
If the effort failed, the provided clazz is used for logging purposes.

Parameters:

clazz - to use for logging should the effort fail.

fc - to prevent from automatically closing upon interrupt.

addToClassPath
```
public static void addToClassPath(@NotNull
                                  @NotNull Class<?> clazz)
```
Ensures that all the jars and other resources are added to the class path of the classloader associated by the provided clazz.

Parameters:

clazz - to use as a template.

getDouble
```
public static double getDouble(String systemPropertyKey,
                               double defaultValue)
```
Returns the System Property associated with the provided systemPropertyKey parsed as a double or, if no such parsable System Property exists, returns the provided defaultValue.
Guarantees that Jvm class is initialized before property is read.

Parameters:

systemPropertyKey - to lookup in the System Properties

defaultValue - to be used if no parsable key association exists

Returns:

the System Property associated with the provided systemPropertyKey parsed as a double or, if no such parsable System Property exists, returns the provided defaultValue

isProcessAlive
```
public static boolean isProcessAlive(long pid)
```
Returns if a process with the provided pid process id is alive.

Parameters:

pid - the process id (pid) of the process to check

Returns:

if a process with the provided pid process id is alive

isAzulZing
```
public static boolean isAzulZing()
```

isAzulZulu
```
public static boolean isAzulZulu()
```

getCpuClass
```
public static String getCpuClass()
```
Returns:

Obtain the model of CPU on Linux or the os.arch on other OSes.

isAssertEnabled
```
public static boolean isAssertEnabled()
```
Was assertion enabled for the Jvm class when it was initialised.

Returns:

if assertions were enabled.

supportThread
```
public static boolean supportThread()
```

park
```
public static void park()
```
park the current thread, and stay parked

findAnnotation
```
public static <A extends Annotation> A findAnnotation(AnnotatedElement annotatedElement,
                                                      Class<A> annotationType)
```
Retrieve an annotation of the specified annotationType that is present on the given annotatedElement, including considering nested annotations and method inheritance. If the annotation isn't found, this method returns null.

Type Parameters:

A - denotes the annotation type.

Parameters:

annotatedElement - the element (e.g., class, method, field) to inspect for annotations.

annotationType - the desired annotation's type.

Returns:

the found annotation of type A or null if not present.

isLambdaClass
```
public static boolean isLambdaClass(Class<?> clazz)
```
Checks if the given class represents a lambda expression.
Java creates synthetic classes for lambda expressions. Typically, the name of these classes contains the "$$Lambda" substring. Note that this naming convention is JVM-specific and can change in future versions. The approach is known to work up to Java 21.

Parameters:

clazz - the class to be checked.

Returns:

true if the class is a lambda, false otherwise.

uncheckedCast
```
public static <T> T uncheckedCast(Object o)
```
Performs an unchecked cast of an object to the target type T. This method bypasses generic type checks, allowing for casting without explicit type checking, offering a convenient way to avoid compiler warnings for unchecked casts.
Note: Use with caution as improper use can lead to ClassCastException at runtime if the object is not of type T. Intended for situations where the type safety is guaranteed through other means but cannot be expressed without generic type warnings.

Type Parameters:

T - the target type to cast to

Parameters:

o - the object to be cast

Returns:

the casted object of type T

Throws:

ClassCastException - if the object cannot be casted to the target type T (a runtime risk due to type erasure)

uncheckedCast
```
public static <T> T[] uncheckedCast(Object[] o)
```
Performs an unchecked cast of an array of objects to an array of the target type T[]. This method bypasses generic array type checks, facilitating casting without explicit array type checking.
Note: Use with caution as improper use can lead to ClassCastException at runtime if the objects in the array cannot be cast to type T[]. This method is useful when the programmer is confident in the implicit type safety of the operation but wishes to avoid compiler warnings about unchecked operations.

Type Parameters:

T - the target component type of the array to cast to

Parameters:

o - the object array to be cast

Returns:

the casted object array of type T[]

Throws:

ClassCastException - if the objects in the array cannot be cast to the component type T[]

uncheckedCast
```
public static <T> Class<T> uncheckedCast(Class<?> o)
```
Performs an unchecked cast of a Class object to Class<T>. This operation is particularly useful in scenarios involving reflection where generic type parameters are known but cannot be statically enforced by the compiler.
By bypassing compile-time generic type checks, it provides a way to work with generic types in a dynamic context at the cost of compile-time type safety.
Note: Use with caution as improper use can lead to a ClassCastException at runtime if the class object cannot actually be cast to Class<T>. This method should be employed when there is certainty about the underlying type compatibility.

Type Parameters:

T - the target generic type to cast the class to

Parameters:

o - the class object to be cast

Returns:

the class object cast to Class<T>

Throws:

ClassCastException - if the class object cannot be cast to Class<T> (a runtime risk inherent to unchecked casting)

currentThreadId
```
public static long currentThreadId()
```
Retrieves the unique identifier of the current thread.
This method provides a straightforward way to obtain the ID of the thread from which the method is called. Currently, it uses Thread.currentThread() and Thread.getId() to accomplish this. The method is safe to use across various versions of Java.
Note: In future versions, this implementation may be updated to use Thread.threadId() or another updated mechanism for obtaining the thread ID, as newer Java versions from version 19 deprecate the current approach.

Returns:

the identifier of the current thread

getPackageName
```
public static String getPackageName(Class clazz)
```
Returns the package name of the specified class.
This method uses Class.getPackageName() if running on Java 9 or newer. For older versions, it uses a cached value determined by the class name.

Parameters:

clazz - the class whose package name is to be determined

Returns:

the package name of the specified class

Class Jvm

Nested Class Summary

Field Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

JAVA_CLASS_PATH

SYSTEM_PROPERTIES

Method Detail

reportUnoptimised

init

compileThreshold

majorVersion

isJava9Plus

isJava12Plus

isJava14Plus

isJava15Plus

isJava19Plus

isJava20Plus

isJava21Plus

getProcessId

rethrow

trimStackTrace

trimLast

isDebug

isFlightRecorder

isCodeCoverage

pause

nanoPause

busyWaitMicros

busyWaitUntil

getField

getFieldOrNull

getMethod

setAccessible

getValue

lockWithStack

fieldOffset

usedDirectMemory

usedNativeMemory

maxDirectMemory

is64bit

resetExceptionHandlers

setErrorExceptionHandler

setWarnExceptionHandler

setDebugExceptionHandler

setPerfExceptionHandler

disableDebugHandler

disablePerfHandler

disableWarnHandler

recordExceptions

recordExceptions

recordExceptions

recordExceptions

hasException

setExceptionHandlers

setExceptionHandlers

setThreadLocalExceptionHandlers

setThreadLocalExceptionHandlers

error

warn

startup

perf

debug

dumpException

isDebugEnabled

isPerfEnabled

addSignalHandler

safepoint

areOptionalSafepointsEnabled

stackTraceEndsWith

isArm

isMacArm

classMetrics

userHome

dontChain

isResourceTracing

setResourceTracing

getProperty

getProperty