java.lang Runtime

java.lang
Runtime

Declaration
public class Runtime
java.lang.Object
|
+--java.lang.Runtime
Description
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.
Since: JDK1.0, CLDC 1.0


Methods
void exit(int status)
long freeMemory()
void gc()
static Runtime getRuntime()
long totalMemory()


Methods inherited from class Object
equals(Object), getClass(), hashCode(), notify(), notifyAll(), toString(), wait(),
wait(), wait()


Methods
getRuntime()
Declaration:
public static java.lang.Runtime getRuntime()


exit(int)

Description:
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(int)
Declaration:
public void exit(int status)
Description:
Terminates the currently running Java application. This method never returns normally.
The argument serves as a status code; by convention, a nonzero status code indicates abnormal termination.
Parameters:
status - exit status.
Since: JDK1.0
freeMemory()
Declaration:
public long freeMemory()
Description:
Returns the amount of free memory in the system. 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.
totalMemory()
Declaration:
public long totalMemory()
Description:
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 implementationdependent.
Returns: the total amount of memory currently available for current and future objects, measured in bytes.
gc()
Declaration:
public void gc()
Description:
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 Java Virtual Machine has made its best effort to recycle all
discarded objects.






The name gc stands for “garbage collector”. The Java Virtual Machine performs this recycling process
automatically as needed even if the gc method is not invoked explicitly.
The method System.gc() is the conventional and convenient means of invoking this method.