Returns the amount of memory available for use by the Java program. - Java Java Virtual Machine

Java examples for Java Virtual Machine:Memory

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Description

Returns the amount of memory available for use by the Java program.

Demo Code

/*//from  w w  w .j a  v  a2 s . co m
 * Copyright (c) 2010-2013, University of Sussex
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 * modification, are permitted provided that the following conditions are met:
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 *    software without specific prior written permission.
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 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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 */
//package com.java2s;

public class Main {
    /**
     * Returns the amount of memory available for use by the Java program. This
     * includes memory that has not yet been allocated to the Java Virtual
     * Machine. <p />
     *
     * @return an approximation to the amount of memory that is available for
     *         use by the Java program.
     */
    public static long freeMaxMemory() {
        return maxMemory() - usedMemory();
    }

    /**
     * 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.
     * <p/>
     * Note that this value has no bearing on the actual physical memory
     * availability of the underlying machine, only the upper limit on what the
     * Java Virtual Machine will attempt to allocate.
     *
     * @return the maximum amount of memory that the virtual machine will
     *         attempt to use, measured in bytes
     */
    public static long maxMemory() {
        return Runtime.getRuntime().maxMemory();
    }

    /**
     * Returns the amount of memory currently used by the Java Virtual Machine.
     * The value returned by this method may vary over time. Calling the
     * {@link Runtime#gc()} method may result in a decreasing the value return
     * by usedMemory.
     *
     * @return an approximation to the amount of memory currently used by
     *         allocated objects, measured in bytes.
     */
    public static long usedMemory() {
        return allocatedMemory() - freeAllocatedMemory();
    }

    /**
     * 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.
     *
     * @return total amount of memory currently available for current and future
     *         objects, measured in bytes.
     */
    public static long allocatedMemory() {
        return Runtime.getRuntime().totalMemory();
    }

    /**
     * Returns the amount of free memory in the Java Virtual Machine. Calling
     * the {@link Runtime#gc()} method may result in increasing the value
     * returned by freeMemory.
     *
     * @return an approximation to the total amount of memory currently
     *         available for future allocated objects, measured in bytes.
     */
    public static long freeAllocatedMemory() {
        return Runtime.getRuntime().freeMemory();
    }
}

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