java.lang

Class Runtime

java.lang.Object

java.lang.Runtime

public class Runtime
extends Object

Every Java application has a single instance of class Runtime that allows the application to interface with the environment in which the application is running. The current runtime can be obtained from the getRuntime method.

An application cannot create its own instance of this class.

See Also:

getRuntime()

Method Summary

Methods

Modifier and Type	Method and Description
void	exit(int status) Terminates the currently running Java virtual machine by initiating its shutdown sequence.
long	freeMemory() Returns the amount of free memory in the Java Virtual Machine.
void	gc() Runs the garbage collector.
static Runtime	getRuntime() Returns the runtime object associated with the current Java application.
long	maxMemory() Returns the maximum amount of memory that the Java virtual machine will attempt to use.
long	totalMemory() Returns the total amount of memory in the Java virtual machine.

Methods inherited from class java.lang.Object

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

Method Detail

getRuntime

public static Runtime getRuntime()

Returns the runtime object associated with the current Java application. Most of the methods of class Runtime are instance methods and must be invoked with respect to the current runtime object.

Returns:

the Runtime object associated with the current Java application.

exit

public void exit(int status)

Terminates the currently running Java virtual machine by initiating its shutdown sequence. This method never returns normally. The argument serves as a status code; by convention, a nonzero status code indicates abnormal termination.

The System.exit method is the conventional and convenient means of invoking this method.

Parameters:

status - Termination status. By convention, a nonzero status code indicates abnormal termination.

freeMemory

public long freeMemory()

Returns the amount of free memory in the Java Virtual Machine. Calling the gc method may result in increasing the value returned by freeMemory.

Returns:

an approximation to the total amount of memory currently available for future allocated objects, measured in bytes.

gc

public void gc()

Runs the garbage collector. Calling this method suggests that the Java virtual machine expend effort toward recycling unused objects in order to make the memory they currently occupy available for quick reuse. When control returns from the method call, the virtual machine has made its best effort to recycle all discarded objects.

The name gc stands for "garbage collector". The virtual machine performs this recycling process automatically as needed, in a separate thread, even if the gc method is not invoked explicitly.

The method System.gc() is the conventional and convenient means of invoking this method.

maxMemory

public long maxMemory()

Returns the maximum amount of memory that the Java virtual machine will attempt to use. If there is no inherent limit then the value Long.MAX_VALUE will be returned.

Returns:

the maximum amount of memory that the virtual machine will attempt to use, measured in bytes

totalMemory

public long totalMemory()

Returns the total amount of memory in the Java virtual machine. The value returned by this method may vary over time, depending on the host environment.

Note that the amount of memory required to hold an object of any given type may be implementation-dependent.

Returns:

the total amount of memory currently available for current and future objects, measured in bytes.