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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* accompanied this code).
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* 2 along with this work; if not, write to the Free Software Foundation,
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package java.lang.management;
import javax.management.openmbean.CompositeData;
import sun.management.MemoryUsageCompositeData;
/**
* A {@code MemoryUsage} object represents a snapshot of memory usage.
* Instances of the {@code MemoryUsage} class are usually constructed
* by methods that are used to obtain memory usage
* information about individual memory pool of the Java virtual machine or
* the heap or non-heap memory of the Java virtual machine as a whole.
*
* <p> A {@code MemoryUsage} object contains four values:
* <table class="striped">
* <caption style="display:none">Describes the MemoryUsage object content</caption>
* <thead>
* <tr><th scope="col">Value</th><th scope="col">Description</th></tr>
* </thead>
* <tbody style="text-align:left">
* <tr>
* <th scope="row" style="vertical-align:top"> {@code init} </th>
* <td style="vertical-align:top"> represents the initial amount of memory (in bytes) that
* the Java virtual machine requests from the operating system
* for memory management during startup. The Java virtual machine
* may request additional memory from the operating system and
* may also release memory to the system over time.
* The value of {@code init} may be undefined.
* </td>
* </tr>
* <tr>
* <th scope="row" style="vertical-align:top"> {@code used} </th>
* <td style="vertical-align:top"> represents the amount of memory currently used (in bytes).
* </td>
* </tr>
* <tr>
* <th scope="row" style="vertical-align:top"> {@code committed} </th>
* <td style="vertical-align:top"> represents the amount of memory (in bytes) that is
* guaranteed to be available for use by the Java virtual machine.
* The amount of committed memory may change over time (increase
* or decrease). The Java virtual machine may release memory to
* the system and {@code committed} could be less than {@code init}.
* {@code committed} will always be greater than
* or equal to {@code used}.
* </td>
* </tr>
* <tr>
* <th scope="row" style="vertical-align:top"> {@code max} </th>
* <td style="vertical-align:top"> represents the maximum amount of memory (in bytes)
* that can be used for memory management. Its value may be undefined.
* The maximum amount of memory may change over time if defined.
* The amount of used and committed memory will always be less than
* or equal to {@code max} if {@code max} is defined.
* A memory allocation may fail if it attempts to increase the
* used memory such that {@code used > committed} even
* if {@code used <= max} would still be true (for example,
* when the system is low on virtual memory).
* </td>
* </tr>
* </tbody>
* </table>
*
* Below is a picture showing an example of a memory pool:
*
* <pre>
* +----------------------------------------------+
* +//////////////// | +
* +//////////////// | +
* +----------------------------------------------+
*
* |--------|
* init
* |---------------|
* used
* |---------------------------|
* committed
* |----------------------------------------------|
* max
* </pre>
*
* <h3>MXBean Mapping</h3>
* {@code MemoryUsage} is mapped to a {@link CompositeData CompositeData}
* with attributes as specified in the {@link #from from} method.
*
* @author Mandy Chung
* @since 1.5
*/
public class MemoryUsage {
private final long init;
private final long used;
private final long committed;
private final long max;
/**
* Constructs a {@code MemoryUsage} object.
*
* @param init the initial amount of memory in bytes that
* the Java virtual machine allocates;
* or {@code -1} if undefined.
* @param used the amount of used memory in bytes.
* @param committed the amount of committed memory in bytes.
* @param max the maximum amount of memory in bytes that
* can be used; or {@code -1} if undefined.
*
* @throws IllegalArgumentException if
* <ul>
* <li> the value of {@code init} or {@code max} is negative
* but not {@code -1}; or</li>
* <li> the value of {@code used} or {@code committed} is negative;
* or</li>
* <li> {@code used} is greater than the value of {@code committed};
* or</li>
* <li> {@code committed} is greater than the value of {@code max}
* {@code max} if defined.</li>
* </ul>
*/
public MemoryUsage(long init,
long used,
long committed,
long max) {
if (init < -1) {
throw new IllegalArgumentException( "init parameter = " +
init + " is negative but not -1.");
}
if (max < -1) {
throw new IllegalArgumentException( "max parameter = " +
max + " is negative but not -1.");
}
if (used < 0) {
throw new IllegalArgumentException( "used parameter = " +
used + " is negative.");
}
if (committed < 0) {
throw new IllegalArgumentException( "committed parameter = " +
committed + " is negative.");
}
if (used > committed) {
throw new IllegalArgumentException( "used = " + used +
" should be <= committed = " + committed);
}
if (max >= 0 && committed > max) {
throw new IllegalArgumentException( "committed = " + committed +
" should be < max = " + max);
}
this.init = init;
this.used = used;
this.committed = committed;
this.max = max;
}
/**
* Constructs a {@code MemoryUsage} object from a
* {@link CompositeData CompositeData}.
*/
private MemoryUsage(CompositeData cd) {
// validate the input composite data
MemoryUsageCompositeData.validateCompositeData(cd);
this.init = MemoryUsageCompositeData.getInit(cd);
this.used = MemoryUsageCompositeData.getUsed(cd);
this.committed = MemoryUsageCompositeData.getCommitted(cd);
this.max = MemoryUsageCompositeData.getMax(cd);
}
/**
* Returns the amount of memory in bytes that the Java virtual machine
* initially requests from the operating system for memory management.
* This method returns {@code -1} if the initial memory size is undefined.
*
* @return the initial size of memory in bytes;
* {@code -1} if undefined.
*/
public long getInit() {
return init;
}
/**
* Returns the amount of used memory in bytes.
*
* @return the amount of used memory in bytes.
*
*/
public long getUsed() {
return used;
};
/**
* Returns the amount of memory in bytes that is committed for
* the Java virtual machine to use. This amount of memory is
* guaranteed for the Java virtual machine to use.
*
* @return the amount of committed memory in bytes.
*
*/
public long getCommitted() {
return committed;
};
/**
* Returns the maximum amount of memory in bytes that can be
* used for memory management. This method returns {@code -1}
* if the maximum memory size is undefined.
*
* <p> This amount of memory is not guaranteed to be available
* for memory management if it is greater than the amount of
* committed memory. The Java virtual machine may fail to allocate
* memory even if the amount of used memory does not exceed this
* maximum size.
*
* @return the maximum amount of memory in bytes;
* {@code -1} if undefined.
*/
public long getMax() {
return max;
};
/**
* Returns a descriptive representation of this memory usage.
*/
public String toString() {
StringBuilder buf = new StringBuilder();
buf.append("init = " + init + "(" + (init >> 10) + "K) ");
buf.append("used = " + used + "(" + (used >> 10) + "K) ");
buf.append("committed = " + committed + "(" +
(committed >> 10) + "K) " );
buf.append("max = " + max + "(" + (max >> 10) + "K)");
return buf.toString();
}
/**
* Returns a {@code MemoryUsage} object represented by the
* given {@code CompositeData}. The given {@code CompositeData}
* must contain the following attributes:
*
* <table class="striped" style="margin-left:2em;">
* <caption style="display:none">The attributes and the types the given CompositeData contains</caption>
* <thead>
* <tr>
* <th scope="col">Attribute Name</th>
* <th scope="col">Type</th>
* </tr>
* </thead>
* <tbody style="text-align:left">
* <tr>
* <th scope="row">init</th>
* <td>{@code java.lang.Long}</td>
* </tr>
* <tr>
* <th scope="row">used</th>
* <td>{@code java.lang.Long}</td>
* </tr>
* <tr>
* <th scope="row">committed</th>
* <td>{@code java.lang.Long}</td>
* </tr>
* <tr>
* <th scope="row">max</th>
* <td>{@code java.lang.Long}</td>
* </tr>
* </tbody>
* </table>
*
* @param cd {@code CompositeData} representing a {@code MemoryUsage}
*
* @throws IllegalArgumentException if {@code cd} does not
* represent a {@code MemoryUsage} with the attributes described
* above.
*
* @return a {@code MemoryUsage} object represented by {@code cd}
* if {@code cd} is not {@code null};
* {@code null} otherwise.
*/
public static MemoryUsage from(CompositeData cd) {
if (cd == null) {
return null;
}
if (cd instanceof MemoryUsageCompositeData) {
return ((MemoryUsageCompositeData) cd).getMemoryUsage();
} else {
return new MemoryUsage(cd);
}
}
}