com.github.azbh111.utils.java.jvm

类 JVM

java.lang.Object

com.github.azbh111.utils.java.jvm.JVM

public class JVM
extends java.lang.Object

方法概要

限定符和类型	方法和说明
java.lang.management.ThreadInfo[]	dumpAllThreads(boolean lockedMonitors, boolean lockedSynchronizers) Returns the thread info for all live threads with stack trace and synchronization information.
long[]	findDeadlockedThreads() Finds cycles of threads that are in deadlock waiting to acquire object monitors or ownable synchronizers.
long[]	findMonitorDeadlockedThreads() Finds cycles of threads that are in deadlock waiting to acquire object monitors.
void	gc() Runs the garbage collector.
long[]	getAllThreadIds() Returns all live thread IDs.
java.lang.String	getArch() Returns the operating system architecture.
int	getAvailableProcessors() Returns the number of processors available to the Java virtual machine.
java.lang.String	getBootClassPath() Returns the boot class path that is used by the bootstrap class loader to search for class files.
java.lang.String	getClassPath() Returns the Java class path that is used by the system class loader to search for class files.
long	getCurrentThreadCpuTime() Returns the total CPU time for the current thread in nanoseconds.
long	getCurrentThreadUserTime() Returns the CPU time that the current thread has executed in user mode in nanoseconds.
int	getDaemonThreadCount() Returns the current number of live daemon threads.
java.util.List<java.lang.management.GarbageCollectorMXBean>	getGarbageCollectorMXBeans()
java.lang.management.MemoryUsage	getHeapMemoryUsage() Returns the current memory usage of the heap that is used for object allocation.
java.util.List<java.lang.String>	getInputArguments() Returns the input arguments passed to the Java virtual machine which does not include the arguments to the main method.
static JVM	getInstance()
java.lang.String	getLibraryPath() Returns the Java library path.
int	getLoadedClassCount() 返回当前加载到 Java 虚拟机中的类的数量 Returns the number of classes that are currently loaded in the Java virtual machine.
java.lang.String	getManagementSpecVersion() Returns the version of the specification for the management interface implemented by the running Java virtual machine.
java.util.List<java.lang.management.MemoryPoolMXBean>	getMemoryPoolMXBeans()
java.lang.String	getName() Returns the name representing the running Java virtual machine.
java.lang.management.MemoryUsage	getNonHeapMemoryUsage() Returns the current memory usage of non-heap memory that is used by the Java virtual machine.
int	getObjectPendingFinalizationCount() Returns the approximate number of objects for which finalization is pending.
int	getPeakThreadCount() 返回自从 Java 虚拟机启动或峰值重置以来峰值活动线程计数 Returns the peak live thread count since the Java virtual machine started or peak was reset.
java.lang.String	getSpecName() Returns the Java virtual machine specification name.
java.lang.String	getSpecVendor() Returns the Java virtual machine specification vendor.
java.lang.String	getSpecVersion() Returns the Java virtual machine specification version.
long	getStartTime() 返回 Java 虚拟机的启动时间（以毫秒为单位） Returns the start time of the Java virtual machine in milliseconds.
double	getSystemLoadAverage() 返回最后一分钟内系统加载平均值 Returns the system load average for the last minute.
java.util.Map<java.lang.String,java.lang.String>	getSystemProperties() Returns a map of names and values of all system properties.
int	getThreadCount() 返回活动线程的当前数目，包括守护线程和非守护线程 Returns the current number of live threads including both daemon and non-daemon threads.
long	getThreadCpuTime(long id) Returns the total CPU time for a thread of the specified ID in nanoseconds.
java.lang.management.ThreadInfo	getThreadInfo(long id) Returns the thread info for a thread of the specified id with no stack trace.
java.lang.management.ThreadInfo[]	getThreadInfo(long[] ids) Returns the thread info for each thread whose ID is in the input array ids with no stack trace.
java.lang.management.ThreadInfo[]	getThreadInfo(long[] ids, boolean lockedMonitors, boolean lockedSynchronizers) Returns the thread info for each thread whose ID is in the input array ids, with stack trace and synchronization information.
java.lang.management.ThreadInfo[]	getThreadInfo(long[] ids, int maxDepth) Returns the thread info for each thread whose ID is in the input array ids, with stack trace of a specified number of stack trace elements.
java.lang.management.ThreadInfo	getThreadInfo(long id, int maxDepth) Returns a thread info for a thread of the specified id, with stack trace of a specified number of stack trace elements.
long	getThreadUserTime(long id) Returns the CPU time that a thread of the specified ID has executed in user mode in nanoseconds.
long	getTotalLoadedClassCount() 返回自 Java 虚拟机开始执行到目前已经加载的类的总数 Returns the total number of classes that have been loaded since the Java virtual machine has started execution.
long	getTotalStartedThreadCount() 返回自从 Java 虚拟机启动以来创建和启动的线程总数目 Returns the total number of threads created and also started since the Java virtual machine started.
long	getUnloadedClassCount() 返回自 Java 虚拟机开始执行到目前已经卸载的类的总数 Returns the total number of classes unloaded since the Java virtual machine has started execution.
long	getUptime() 返回 Java 虚拟机的正常运行时间（以毫秒为单位） Returns the uptime of the Java virtual machine in milliseconds.
java.lang.String	getVersion() Returns the operating system version.
java.lang.String	getVmName() Returns the Java virtual machine implementation name.
java.lang.String	getVmVendor() Returns the Java virtual machine implementation vendor.
java.lang.String	getVmVersion() Returns the Java virtual machine implementation version.
boolean	isBootClassPathSupported() Tests if the Java virtual machine supports the boot class path mechanism used by the bootstrap class loader to search for class files.
boolean	isCurrentThreadCpuTimeSupported() Tests if the Java virtual machine supports CPU time measurement for the current thread.
boolean	isObjectMonitorUsageSupported() Tests if the Java virtual machine supports monitoring of object monitor usage.
boolean	isSynchronizerUsageSupported() Tests if the Java virtual machine supports monitoring of ownable synchronizer usage.
boolean	isThreadContentionMonitoringEnabled() Tests if thread contention monitoring is enabled.
boolean	isThreadContentionMonitoringSupported() Tests if the Java virtual machine supports thread contention monitoring.
boolean	isThreadCpuTimeEnabled() Tests if thread CPU time measurement is enabled.
boolean	isThreadCpuTimeSupported() Tests if the Java virtual machine implementation supports CPU time measurement for any thread.
void	resetPeakThreadCount() Resets the peak thread count to the current number of live threads.
void	setThreadContentionMonitoringEnabled(boolean enable) Enables or disables thread contention monitoring.
void	setThreadCpuTimeEnabled(boolean enable) Enables or disables thread CPU time measurement.

从类继承的方法 java.lang.Object

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

方法详细资料

getInstance

public static JVM getInstance()

getGarbageCollectorMXBeans

public java.util.List<java.lang.management.GarbageCollectorMXBean> getGarbageCollectorMXBeans()

getMemoryPoolMXBeans

public java.util.List<java.lang.management.MemoryPoolMXBean> getMemoryPoolMXBeans()

getObjectPendingFinalizationCount

public int getObjectPendingFinalizationCount()

Returns the approximate number of objects for which finalization is pending.

返回:

the approximate number objects for which finalization is pending.

getHeapMemoryUsage

public java.lang.management.MemoryUsage getHeapMemoryUsage()

Returns the current memory usage of the heap that is used for object allocation. The heap consists of one or more memory pools. The used and committed size of the returned memory usage is the sum of those values of all heap memory pools whereas the init and max size of the returned memory usage represents the setting of the heap memory which may not be the sum of those of all heap memory pools.

The amount of used memory in the returned memory usage is the amount of memory occupied by both live objects and garbage objects that have not been collected, if any.

MBeanServer access:
The mapped type of MemoryUsage is CompositeData with attributes as specified in MemoryUsage.

返回:

a MemoryUsage object representing the heap memory usage.

getNonHeapMemoryUsage

public java.lang.management.MemoryUsage getNonHeapMemoryUsage()

Returns the current memory usage of non-heap memory that is used by the Java virtual machine. The non-heap memory consists of one or more memory pools. The used and committed size of the returned memory usage is the sum of those values of all non-heap memory pools whereas the init and max size of the returned memory usage represents the setting of the non-heap memory which may not be the sum of those of all non-heap memory pools.

MBeanServer access:
The mapped type of MemoryUsage is CompositeData with attributes as specified in MemoryUsage.

返回:

a MemoryUsage object representing the non-heap memory usage.

gc

public void gc()

Runs the garbage collector. The call gc() is effectively equivalent to the call:

 System.gc()
 

另请参阅:

System.gc()

getArch

public java.lang.String getArch()

Returns the operating system architecture. This method is equivalent to System.getProperty("os.arch").

返回:

the operating system architecture.

抛出:

java.lang.SecurityException - if a security manager exists and its checkPropertiesAccess method doesn't allow access to this system property.

另请参阅:

SecurityManager.checkPropertyAccess(String), System.getProperty(java.lang.String)

getVersion

public java.lang.String getVersion()

Returns the operating system version. This method is equivalent to System.getProperty("os.version").

返回:

the operating system version.

抛出:

java.lang.SecurityException - if a security manager exists and its checkPropertiesAccess method doesn't allow access to this system property.

另请参阅:

SecurityManager.checkPropertyAccess(String), System.getProperty(java.lang.String)

getAvailableProcessors

public int getAvailableProcessors()

Returns the number of processors available to the Java virtual machine. This method is equivalent to the Runtime.availableProcessors() method.

This value may change during a particular invocation of the virtual machine.

返回:

the number of processors available to the virtual machine; never smaller than one.

getSystemLoadAverage

public double getSystemLoadAverage()

返回最后一分钟内系统加载平均值 Returns the system load average for the last minute. The system load average is the sum of the number of runnable entities queued to the available processors and the number of runnable entities running on the available processors averaged over a period of time. The way in which the load average is calculated is operating system specific but is typically a damped time-dependent average.

If the load average is not available, a negative value is returned.

This method is designed to provide a hint about the system load and may be queried frequently. The load average may be unavailable on some platform where it is expensive to implement this method.

返回:

the system load average; or a negative value if not available.

从以下版本开始:

1.6

getTotalLoadedClassCount

public long getTotalLoadedClassCount()

返回自 Java 虚拟机开始执行到目前已经加载的类的总数 Returns the total number of classes that have been loaded since the Java virtual machine has started execution.

返回:

the total number of classes loaded.

getLoadedClassCount

public int getLoadedClassCount()

返回当前加载到 Java 虚拟机中的类的数量 Returns the number of classes that are currently loaded in the Java virtual machine.

返回:

the number of currently loaded classes.

getUnloadedClassCount

public long getUnloadedClassCount()

返回自 Java 虚拟机开始执行到目前已经卸载的类的总数 Returns the total number of classes unloaded since the Java virtual machine has started execution.

返回:

the total number of unloaded classes.

getThreadCount

public int getThreadCount()

返回活动线程的当前数目，包括守护线程和非守护线程 Returns the current number of live threads including both daemon and non-daemon threads.

返回:

the current number of live threads.

getPeakThreadCount

public int getPeakThreadCount()

返回自从 Java 虚拟机启动或峰值重置以来峰值活动线程计数 Returns the peak live thread count since the Java virtual machine started or peak was reset.

返回:

the peak live thread count.

getTotalStartedThreadCount

public long getTotalStartedThreadCount()

返回自从 Java 虚拟机启动以来创建和启动的线程总数目 Returns the total number of threads created and also started since the Java virtual machine started.

返回:

the total number of threads started.

getDaemonThreadCount

public int getDaemonThreadCount()

Returns the current number of live daemon threads.

返回:

the current number of live daemon threads.

getAllThreadIds

public long[] getAllThreadIds()

Returns all live thread IDs. Some threads included in the returned array may have been terminated when this method returns.

返回:

an array of long, each is a thread ID.

抛出:

java.lang.SecurityException - if a security manager exists and the caller does not have ManagementPermission("monitor").

getThreadInfo

public java.lang.management.ThreadInfo getThreadInfo(long id)

Returns the thread info for a thread of the specified id with no stack trace. This method is equivalent to calling:

getThreadInfo(id, 0);

This method returns a ThreadInfo object representing the thread information for the thread of the specified ID. The stack trace, locked monitors, and locked synchronizers in the returned ThreadInfo object will be empty. If a thread of the given ID is not alive or does not exist, this method will return null. A thread is alive if it has been started and has not yet died.

MBeanServer access:
The mapped type of ThreadInfo is CompositeData with attributes as specified in the ThreadInfo.from method.

参数:

id - the thread ID of the thread. Must be positive.

返回:

a ThreadInfo object for the thread of the given ID with no stack trace, no locked monitor and no synchronizer info; null if the thread of the given ID is not alive or it does not exist.

抛出:

java.lang.IllegalArgumentException - if id <= 0.

java.lang.SecurityException - if a security manager exists and the caller does not have ManagementPermission("monitor").

getThreadInfo

public java.lang.management.ThreadInfo[] getThreadInfo(long[] ids)

Returns the thread info for each thread whose ID is in the input array ids with no stack trace. This method is equivalent to calling:

   getThreadInfo(ids, 0);
 

This method returns an array of the ThreadInfo objects. The stack trace, locked monitors, and locked synchronizers in each ThreadInfo object will be empty. If a thread of a given ID is not alive or does not exist, the corresponding element in the returned array will contain null. A thread is alive if it has been started and has not yet died.

MBeanServer access:
The mapped type of ThreadInfo is CompositeData with attributes as specified in the ThreadInfo.from method.

参数:

ids - an array of thread IDs.

返回:

an array of the ThreadInfo objects, each containing information about a thread whose ID is in the corresponding element of the input array of IDs with no stack trace, no locked monitor and no synchronizer info.

抛出:

java.lang.IllegalArgumentException - if any element in the input array ids is <= 0.

java.lang.SecurityException - if a security manager exists and the caller does not have ManagementPermission("monitor").

getThreadInfo

public java.lang.management.ThreadInfo getThreadInfo(long id,
                                                     int maxDepth)

Returns a thread info for a thread of the specified id, with stack trace of a specified number of stack trace elements. The maxDepth parameter indicates the maximum number of StackTraceElement to be retrieved from the stack trace. If maxDepth == Integer.MAX_VALUE, the entire stack trace of the thread will be dumped. If maxDepth == 0, no stack trace of the thread will be dumped. This method does not obtain the locked monitors and locked synchronizers of the thread.

When the Java virtual machine has no stack trace information about a thread or maxDepth == 0, the stack trace in the ThreadInfo object will be an empty array of StackTraceElement.

If a thread of the given ID is not alive or does not exist, this method will return null. A thread is alive if it has been started and has not yet died.

MBeanServer access:
The mapped type of ThreadInfo is CompositeData with attributes as specified in the ThreadInfo.from method.

参数:

id - the thread ID of the thread. Must be positive.

maxDepth - the maximum number of entries in the stack trace to be dumped. Integer.MAX_VALUE could be used to request the entire stack to be dumped.

返回:

a ThreadInfo of the thread of the given ID with no locked monitor and synchronizer info. null if the thread of the given ID is not alive or it does not exist.

抛出:

java.lang.IllegalArgumentException - if id <= 0.

java.lang.IllegalArgumentException - if maxDepth is negative.

java.lang.SecurityException - if a security manager exists and the caller does not have ManagementPermission("monitor").

getThreadInfo

public java.lang.management.ThreadInfo[] getThreadInfo(long[] ids,
                                                       int maxDepth)

Returns the thread info for each thread whose ID is in the input array ids, with stack trace of a specified number of stack trace elements. The maxDepth parameter indicates the maximum number of StackTraceElement to be retrieved from the stack trace. If maxDepth == Integer.MAX_VALUE, the entire stack trace of the thread will be dumped. If maxDepth == 0, no stack trace of the thread will be dumped. This method does not obtain the locked monitors and locked synchronizers of the threads.

When the Java virtual machine has no stack trace information about a thread or maxDepth == 0, the stack trace in the ThreadInfo object will be an empty array of StackTraceElement.

This method returns an array of the ThreadInfo objects, each is the thread information about the thread with the same index as in the ids array. If a thread of the given ID is not alive or does not exist, null will be set in the corresponding element in the returned array. A thread is alive if it has been started and has not yet died.

MBeanServer access:
The mapped type of ThreadInfo is CompositeData with attributes as specified in the ThreadInfo.from method.

参数:

ids - an array of thread IDs

maxDepth - the maximum number of entries in the stack trace to be dumped. Integer.MAX_VALUE could be used to request the entire stack to be dumped.

返回:

an array of the ThreadInfo objects, each containing information about a thread whose ID is in the corresponding element of the input array of IDs with no locked monitor and synchronizer info.

抛出:

java.lang.IllegalArgumentException - if maxDepth is negative.

java.lang.IllegalArgumentException - if any element in the input array ids is <= 0.

java.lang.SecurityException - if a security manager exists and the caller does not have ManagementPermission("monitor").

isThreadContentionMonitoringSupported

public boolean isThreadContentionMonitoringSupported()

Tests if the Java virtual machine supports thread contention monitoring.

返回:

true if the Java virtual machine supports thread contention monitoring; false otherwise.

isThreadContentionMonitoringEnabled

public boolean isThreadContentionMonitoringEnabled()

Tests if thread contention monitoring is enabled.

返回:

true if thread contention monitoring is enabled; false otherwise.

抛出:

java.lang.UnsupportedOperationException - if the Java virtual machine does not support thread contention monitoring.

另请参阅:

isThreadContentionMonitoringSupported()

setThreadContentionMonitoringEnabled

public void setThreadContentionMonitoringEnabled(boolean enable)

Enables or disables thread contention monitoring. Thread contention monitoring is disabled by default.

参数:

enable - true to enable; false to disable.

抛出:

java.lang.UnsupportedOperationException - if the Java virtual machine does not support thread contention monitoring.

java.lang.SecurityException - if a security manager exists and the caller does not have ManagementPermission("control").

另请参阅:

isThreadContentionMonitoringSupported()

getCurrentThreadCpuTime

public long getCurrentThreadCpuTime()

Returns the total CPU time for the current thread in nanoseconds. The returned value is of nanoseconds precision but not necessarily nanoseconds accuracy. If the implementation distinguishes between user mode time and system mode time, the returned CPU time is the amount of time that the current thread has executed in user mode or system mode.

This is a convenient method for local management use and is equivalent to calling:

   getThreadCpuTime(Thread.currentThread().getId());
 

返回:

the total CPU time for the current thread if CPU time measurement is enabled; -1 otherwise.

抛出:

java.lang.UnsupportedOperationException - if the Java virtual machine does not support CPU time measurement for the current thread.

另请参阅:

getCurrentThreadUserTime(), isCurrentThreadCpuTimeSupported(), isThreadCpuTimeEnabled(), setThreadCpuTimeEnabled(boolean)

getCurrentThreadUserTime

public long getCurrentThreadUserTime()

Returns the CPU time that the current thread has executed in user mode in nanoseconds. The returned value is of nanoseconds precision but not necessarily nanoseconds accuracy.

This is a convenient method for local management use and is equivalent to calling:

   getThreadUserTime(Thread.currentThread().getId());
 

返回:

the user-level CPU time for the current thread if CPU time measurement is enabled; -1 otherwise.

抛出:

java.lang.UnsupportedOperationException - if the Java virtual machine does not support CPU time measurement for the current thread.

另请参阅:

getCurrentThreadCpuTime(), isCurrentThreadCpuTimeSupported(), isThreadCpuTimeEnabled(), setThreadCpuTimeEnabled(boolean)

getThreadCpuTime

public long getThreadCpuTime(long id)

Returns the total CPU time for a thread of the specified ID in nanoseconds. The returned value is of nanoseconds precision but not necessarily nanoseconds accuracy. If the implementation distinguishes between user mode time and system mode time, the returned CPU time is the amount of time that the thread has executed in user mode or system mode.

If the thread of the specified ID is not alive or does not exist, this method returns -1. If CPU time measurement is disabled, this method returns -1. A thread is alive if it has been started and has not yet died.

If CPU time measurement is enabled after the thread has started, the Java virtual machine implementation may choose any time up to and including the time that the capability is enabled as the point where CPU time measurement starts.

参数:

id - the thread ID of a thread

返回:

the total CPU time for a thread of the specified ID if the thread of the specified ID exists, the thread is alive, and CPU time measurement is enabled; -1 otherwise.

抛出:

java.lang.IllegalArgumentException - if id <= 0.

java.lang.UnsupportedOperationException - if the Java virtual machine does not support CPU time measurement for other threads.

另请参阅:

getThreadUserTime(long), isThreadCpuTimeSupported(), isThreadCpuTimeEnabled(), setThreadCpuTimeEnabled(boolean)

getThreadUserTime

public long getThreadUserTime(long id)

Returns the CPU time that a thread of the specified ID has executed in user mode in nanoseconds. The returned value is of nanoseconds precision but not necessarily nanoseconds accuracy.

If the thread of the specified ID is not alive or does not exist, this method returns -1. If CPU time measurement is disabled, this method returns -1. A thread is alive if it has been started and has not yet died.

If CPU time measurement is enabled after the thread has started, the Java virtual machine implementation may choose any time up to and including the time that the capability is enabled as the point where CPU time measurement starts.

参数:

id - the thread ID of a thread

返回:

the user-level CPU time for a thread of the specified ID if the thread of the specified ID exists, the thread is alive, and CPU time measurement is enabled; -1 otherwise.

抛出:

java.lang.IllegalArgumentException - if id <= 0.

java.lang.UnsupportedOperationException - if the Java virtual machine does not support CPU time measurement for other threads.

另请参阅:

getThreadCpuTime(long), isThreadCpuTimeSupported(), isThreadCpuTimeEnabled(), setThreadCpuTimeEnabled(boolean)

isThreadCpuTimeSupported

public boolean isThreadCpuTimeSupported()

Tests if the Java virtual machine implementation supports CPU time measurement for any thread. A Java virtual machine implementation that supports CPU time measurement for any thread will also support CPU time measurement for the current thread.

返回:

true if the Java virtual machine supports CPU time measurement for any thread; false otherwise.

isCurrentThreadCpuTimeSupported

public boolean isCurrentThreadCpuTimeSupported()

Tests if the Java virtual machine supports CPU time measurement for the current thread. This method returns true if isThreadCpuTimeSupported() returns true.

返回:

true if the Java virtual machine supports CPU time measurement for current thread; false otherwise.

isThreadCpuTimeEnabled

public boolean isThreadCpuTimeEnabled()

Tests if thread CPU time measurement is enabled.

返回:

true if thread CPU time measurement is enabled; false otherwise.

抛出:

java.lang.UnsupportedOperationException - if the Java virtual machine does not support CPU time measurement for other threads nor for the current thread.

另请参阅:

isThreadCpuTimeSupported(), isCurrentThreadCpuTimeSupported()

setThreadCpuTimeEnabled

public void setThreadCpuTimeEnabled(boolean enable)

Enables or disables thread CPU time measurement. The default is platform dependent.

参数:

enable - true to enable; false to disable.

抛出:

java.lang.UnsupportedOperationException - if the Java virtual machine does not support CPU time measurement for any threads nor for the current thread.

java.lang.SecurityException - if a security manager exists and the caller does not have ManagementPermission("control").

另请参阅:

isThreadCpuTimeSupported(), isCurrentThreadCpuTimeSupported()

findMonitorDeadlockedThreads

public long[] findMonitorDeadlockedThreads()

Finds cycles of threads that are in deadlock waiting to acquire object monitors. That is, threads that are blocked waiting to enter a synchronization block or waiting to reenter a synchronization block after an Object.wait call, where each thread owns one monitor while trying to obtain another monitor already held by another thread in a cycle.

More formally, a thread is monitor deadlocked if it is part of a cycle in the relation "is waiting for an object monitor owned by". In the simplest case, thread A is blocked waiting for a monitor owned by thread B, and thread B is blocked waiting for a monitor owned by thread A.

This method is designed for troubleshooting use, but not for synchronization control. It might be an expensive operation.

This method finds deadlocks involving only object monitors. To find deadlocks involving both object monitors and ownable synchronizers, the findDeadlockedThreads method should be used.

返回:

an array of IDs of the threads that are monitor deadlocked, if any; null otherwise.

抛出:

java.lang.SecurityException - if a security manager exists and the caller does not have ManagementPermission("monitor").

另请参阅:

findDeadlockedThreads()

resetPeakThreadCount

public void resetPeakThreadCount()

Resets the peak thread count to the current number of live threads.

抛出:

java.lang.SecurityException - if a security manager exists and the caller does not have ManagementPermission("control").

另请参阅:

getPeakThreadCount(), getThreadCount()

findDeadlockedThreads

public long[] findDeadlockedThreads()

Finds cycles of threads that are in deadlock waiting to acquire object monitors or ownable synchronizers. Threads are deadlocked in a cycle waiting for a lock of these two types if each thread owns one lock while trying to acquire another lock already held by another thread in the cycle.

This method is designed for troubleshooting use, but not for synchronization control. It might be an expensive operation.

返回:

an array of IDs of the threads that are deadlocked waiting for object monitors or ownable synchronizers, if any; null otherwise.

抛出:

java.lang.SecurityException - if a security manager exists and the caller does not have ManagementPermission("monitor").

java.lang.UnsupportedOperationException - if the Java virtual machine does not support monitoring of ownable synchronizer usage.

从以下版本开始:

1.6

另请参阅:

isSynchronizerUsageSupported(), findMonitorDeadlockedThreads()

isObjectMonitorUsageSupported

public boolean isObjectMonitorUsageSupported()

Tests if the Java virtual machine supports monitoring of object monitor usage.

返回:

true if the Java virtual machine supports monitoring of object monitor usage; false otherwise.

从以下版本开始:

1.6

另请参阅:

dumpAllThreads(boolean, boolean)

isSynchronizerUsageSupported

public boolean isSynchronizerUsageSupported()

Tests if the Java virtual machine supports monitoring of ownable synchronizer usage.

返回:

true if the Java virtual machine supports monitoring of ownable synchronizer usage; false otherwise.

从以下版本开始:

1.6

另请参阅:

dumpAllThreads(boolean, boolean)

getThreadInfo

public java.lang.management.ThreadInfo[] getThreadInfo(long[] ids,
                                                       boolean lockedMonitors,
                                                       boolean lockedSynchronizers)

Returns the thread info for each thread whose ID is in the input array ids, with stack trace and synchronization information.

This method obtains a snapshot of the thread information for each thread including:

• the entire stack trace,
• the object monitors currently locked by the thread if lockedMonitors is true, and
• the ownable synchronizers currently locked by the thread if lockedSynchronizers is true.

This method returns an array of the ThreadInfo objects, each is the thread information about the thread with the same index as in the ids array. If a thread of the given ID is not alive or does not exist, null will be set in the corresponding element in the returned array. A thread is alive if it has been started and has not yet died.

If a thread does not lock any object monitor or lockedMonitors is false, the returned ThreadInfo object will have an empty MonitorInfo array. Similarly, if a thread does not lock any synchronizer or lockedSynchronizers is false, the returned ThreadInfo object will have an empty LockInfo array.

When both lockedMonitors and lockedSynchronizers parameters are false, it is equivalent to calling:

     getThreadInfo(ids, Integer.MAX_VALUE)
 

This method is designed for troubleshooting use, but not for synchronization control. It might be an expensive operation.

MBeanServer access:
The mapped type of ThreadInfo is CompositeData with attributes as specified in the ThreadInfo.from method.

参数:

ids - an array of thread IDs.

lockedMonitors - if true, retrieves all locked monitors.

lockedSynchronizers - if true, retrieves all locked ownable synchronizers.

返回:

an array of the ThreadInfo objects, each containing information about a thread whose ID is in the corresponding element of the input array of IDs.

抛出:

java.lang.SecurityException - if a security manager exists and the caller does not have ManagementPermission("monitor").

java.lang.UnsupportedOperationException -

• if lockedMonitors is true but the Java virtual machine does not support monitoring of object monitor usage; or
• if lockedSynchronizers is true but the Java virtual machine does not support monitoring of ownable synchronizer usage.

从以下版本开始:

1.6

另请参阅:

isObjectMonitorUsageSupported(), isSynchronizerUsageSupported()

dumpAllThreads

public java.lang.management.ThreadInfo[] dumpAllThreads(boolean lockedMonitors,
                                                        boolean lockedSynchronizers)

Returns the thread info for all live threads with stack trace and synchronization information. Some threads included in the returned array may have been terminated when this method returns.

This method returns an array of ThreadInfo objects as specified in the getThreadInfo(long[], boolean, boolean) method.

参数:

lockedMonitors - if true, dump all locked monitors.

lockedSynchronizers - if true, dump all locked ownable synchronizers.

返回:

an array of ThreadInfo for all live threads.

抛出:

java.lang.SecurityException - if a security manager exists and the caller does not have ManagementPermission("monitor").

java.lang.UnsupportedOperationException -

• if lockedMonitors is true but the Java virtual machine does not support monitoring of object monitor usage; or
• if lockedSynchronizers is true but the Java virtual machine does not support monitoring of ownable synchronizer usage.

从以下版本开始:

1.6

另请参阅:

isObjectMonitorUsageSupported(), isSynchronizerUsageSupported()

getName

public java.lang.String getName()

Returns the name representing the running Java virtual machine. The returned name string can be any arbitrary string and a Java virtual machine implementation can choose to embed platform-specific useful information in the returned name string. Each running virtual machine could have a different name.

返回:

the name representing the running Java virtual machine.

getVmName

public java.lang.String getVmName()

Returns the Java virtual machine implementation name. This method is equivalent to System.getProperty("java.vm.name").

返回:

the Java virtual machine implementation name.

抛出:

java.lang.SecurityException - if a security manager exists and its checkPropertiesAccess method doesn't allow access to this system property.

另请参阅:

SecurityManager.checkPropertyAccess(String), System.getProperty(java.lang.String)

getVmVendor

public java.lang.String getVmVendor()

Returns the Java virtual machine implementation vendor. This method is equivalent to System.getProperty("java.vm.vendor").

返回:

the Java virtual machine implementation vendor.

抛出:

java.lang.SecurityException - if a security manager exists and its checkPropertiesAccess method doesn't allow access to this system property.

另请参阅:

SecurityManager.checkPropertyAccess(String), System.getProperty(java.lang.String)

getVmVersion

public java.lang.String getVmVersion()

Returns the Java virtual machine implementation version. This method is equivalent to System.getProperty("java.vm.version").

返回:

the Java virtual machine implementation version.

抛出:

java.lang.SecurityException - if a security manager exists and its checkPropertiesAccess method doesn't allow access to this system property.

另请参阅:

SecurityManager.checkPropertyAccess(String), System.getProperty(java.lang.String)

getSpecName

public java.lang.String getSpecName()

Returns the Java virtual machine specification name. This method is equivalent to System.getProperty("java.vm.specification.name").

返回:

the Java virtual machine specification name.

抛出:

java.lang.SecurityException - if a security manager exists and its checkPropertiesAccess method doesn't allow access to this system property.

另请参阅:

SecurityManager.checkPropertyAccess(String), System.getProperty(java.lang.String)

getSpecVendor

public java.lang.String getSpecVendor()

Returns the Java virtual machine specification vendor. This method is equivalent to System.getProperty("java.vm.specification.vendor").

返回:

the Java virtual machine specification vendor.

抛出:

java.lang.SecurityException - if a security manager exists and its checkPropertiesAccess method doesn't allow access to this system property.

另请参阅:

SecurityManager.checkPropertyAccess(String), System.getProperty(java.lang.String)

getSpecVersion

public java.lang.String getSpecVersion()

Returns the Java virtual machine specification version. This method is equivalent to System.getProperty("java.vm.specification.version").

返回:

the Java virtual machine specification version.

抛出:

java.lang.SecurityException - if a security manager exists and its checkPropertiesAccess method doesn't allow access to this system property.

另请参阅:

SecurityManager.checkPropertyAccess(String), System.getProperty(java.lang.String)

getManagementSpecVersion

public java.lang.String getManagementSpecVersion()

Returns the version of the specification for the management interface implemented by the running Java virtual machine.

返回:

the version of the specification for the management interface implemented by the running Java virtual machine.

getClassPath

public java.lang.String getClassPath()

Returns the Java class path that is used by the system class loader to search for class files. This method is equivalent to System.getProperty("java.class.path").

Multiple paths in the Java class path are separated by the path separator character of the platform of the Java virtual machine being monitored.

返回:

the Java class path.

抛出:

java.lang.SecurityException - if a security manager exists and its checkPropertiesAccess method doesn't allow access to this system property.

另请参阅:

SecurityManager.checkPropertyAccess(String), System.getProperty(java.lang.String)

getLibraryPath

public java.lang.String getLibraryPath()

Returns the Java library path. This method is equivalent to System.getProperty("java.library.path").

Multiple paths in the Java library path are separated by the path separator character of the platform of the Java virtual machine being monitored.

返回:

the Java library path.

抛出:

java.lang.SecurityException - if a security manager exists and its checkPropertiesAccess method doesn't allow access to this system property.

另请参阅:

SecurityManager.checkPropertyAccess(String), System.getProperty(java.lang.String)

isBootClassPathSupported

public boolean isBootClassPathSupported()

Tests if the Java virtual machine supports the boot class path mechanism used by the bootstrap class loader to search for class files.

返回:

true if the Java virtual machine supports the class path mechanism; false otherwise.

getBootClassPath

public java.lang.String getBootClassPath()

Returns the boot class path that is used by the bootstrap class loader to search for class files.

Multiple paths in the boot class path are separated by the path separator character of the platform on which the Java virtual machine is running.

A Java virtual machine implementation may not support the boot class path mechanism for the bootstrap class loader to search for class files. The isBootClassPathSupported() method can be used to determine if the Java virtual machine supports this method.

返回:

the boot class path.

抛出:

java.lang.UnsupportedOperationException - if the Java virtual machine does not support this operation.

java.lang.SecurityException - if a security manager exists and the caller does not have ManagementPermission("monitor").

getInputArguments

public java.util.List<java.lang.String> getInputArguments()

Returns the input arguments passed to the Java virtual machine which does not include the arguments to the main method. This method returns an empty list if there is no input argument to the Java virtual machine.

Some Java virtual machine implementations may take input arguments from multiple different sources: for examples, arguments passed from the application that launches the Java virtual machine such as the 'java' command, environment variables, configuration files, etc.

Typically, not all command-line options to the 'java' command are passed to the Java virtual machine. Thus, the returned input arguments may not include all command-line options.

MBeanServer access:
The mapped type of List<String> is String[].

返回:

a list of String objects; each element is an argument passed to the Java virtual machine.

抛出:

java.lang.SecurityException - if a security manager exists and the caller does not have ManagementPermission("monitor").

getUptime

public long getUptime()

返回 Java 虚拟机的正常运行时间（以毫秒为单位） Returns the uptime of the Java virtual machine in milliseconds.

返回:

uptime of the Java virtual machine in milliseconds.

getStartTime

public long getStartTime()

返回 Java 虚拟机的启动时间（以毫秒为单位） Returns the start time of the Java virtual machine in milliseconds. This method returns the approximate time when the Java virtual machine started.

返回:

start time of the Java virtual machine in milliseconds.

getSystemProperties

public java.util.Map<java.lang.String,java.lang.String> getSystemProperties()

Returns a map of names and values of all system properties. This method calls System.getProperties() to get all system properties. Properties whose name or value is not a String are omitted.

MBeanServer access:
The mapped type of Map<String,String> is TabularData with two items in each row as follows:

Item Name	Item Type
key	String
value	String

返回:

a map of names and values of all system properties.

抛出:

java.lang.SecurityException - if a security manager exists and its checkPropertiesAccess method doesn't allow access to the system properties.