repicea.lang

Class MemoryWatchDog

java.lang.Object

repicea.lang.MemoryWatchDog

public class MemoryWatchDog
extends java.lang.Object

This class is used to control the memory before a OutOfMemoryError object is thrown. The class only has one static method that checks the available memory. If the available memory is below a given threshold, the method throws a ExpectedMemoryCapacityException. This kind of exception is derived from RunTimeException. Consequently, there is no need for the method that implements checkAvailabmeMemory() to throw Exception.

The threshold can be set either in terms of percentage of the total memory (through MAXIMUM_PROPORTION_USED public static member) or in terms of minimum free space available in MegaBytes (through MINIMUM_FREE_SPACE public static member). By default, MAXIMUM_PROPORTION_USED is set to 0.9 and MINIMUM_FREE_SPACE is set to 10.

Example of code:

public void myMethod() {

try {

MemoryWatchDog.checkAvailableMemory()
...

} catch (Exception e)

System.out.println(e.getMessage());

}

}

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	MemoryWatchDog.ExpectedMemoryCapacityException This exception class is thrown when the memory is about to exceed its capacity.

Field Summary

Fields

Modifier and Type	Field and Description
static double	MAXIMUM_PROPORTION_USED The maximum proportion of the memory that can be used before throwing an ExpectedMemoryCapacityException.
static double	MINIMUM_FREE_SPACE The minimum memory space that should be free to allow the system to work properly.

Constructor Summary

Constructors

Constructor and Description
MemoryWatchDog()

Method Summary

Modifier and Type	Method and Description
static double	checkAvailableMemory() Checks if the available memory is still above the threshold is used.
static double	checkUsedMemory() Checks the memory that is currently used.

Methods inherited from class java.lang.Object

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

Field Detail

MAXIMUM_PROPORTION_USED

public static double MAXIMUM_PROPORTION_USED

The maximum proportion of the memory that can be used before throwing an ExpectedMemoryCapacityException. A double between 0 to 1. The default value is 0.90 .

MINIMUM_FREE_SPACE

public static double MINIMUM_FREE_SPACE

The minimum memory space that should be free to allow the system to work properly. A double that represents a number of MegaBytes. The default value is set to 10 Mb.

Constructor Detail

MemoryWatchDog

public MemoryWatchDog()

Method Detail

checkAvailableMemory

public static double checkAvailableMemory()
                                   throws MemoryWatchDog.ExpectedMemoryCapacityException

Checks if the available memory is still above the threshold is used. If not, the garbage collector is called and the test is run again. If the available memory is still below the threshold after calling the garbage collector, an ExpectedMemoryCapacityException is thrown.

Returns:

the number of Mg still available

Throws:

a - ExpectedMemoryCapacityException object

MemoryWatchDog.ExpectedMemoryCapacityException

checkUsedMemory

public static double checkUsedMemory()

Checks the memory that is currently used.

Returns:

the memory load in Mg