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A collection of Java utilities.
There is a newer version: 1.9
//
// samskivert library - useful routines for java programs
// Copyright (C) 2001-2012 Michael Bayne, et al.
// http://github.com/samskivert/samskivert/blob/master/COPYING

package com.samskivert.util;

import java.awt.DisplayMode;
import java.awt.GraphicsDevice;
import java.awt.GraphicsEnvironment;

/**
 * A record detailing that gathers and makes available various useful bits
 * of system information.  The record is populated with the current system
 * statistics at construction time, and may be refreshed as desired with a
 * call to {@link #update}.
 */
public class SystemInfo
{
    /** The operating system name. */
    public String osName;

    /** The operating system version. */
    public String osVersion;

    /** The operating system architecture. */
    public String osArch;

    /** The JVM version. */
    public String javaVersion;

    /** The JVM vendor. */
    public String javaVendor;

    /** The amount of free memory in kilobytes. */
    public long freeMemory;

    /** The amount of used memory in kilobytes. */
    public long usedMemory;

    /** The amount of total memory available in kilobytes. */
    public long totalMemory;

    /** The maximum amount of memory available in kilobytes. */
    public long maxMemory;

    /** Whether the video display is headless or video information is
     * unavailable. */
    public boolean isHeadless;

    /** The video display bit depth; see {@link DisplayMode}. */
    public int bitDepth;

    /** The video display refresh rate in kHz; see {@link DisplayMode}. */
    public int refreshRate;

    /** Whether the video display is currently set to full-screen mode. */
    public boolean isFullScreen;

    /** The video display width in pixels. */
    public int displayWidth;

    /** The video display height in pixels. */
    public int displayHeight;

    /**
     * Constructs a system info object.
     */
    public SystemInfo ()
    {
        // gather initial system info
        update();
    }

    /**
     * Updates the system info record's statistics to reflect the current
     * state of the JVM.
     */
    public void update ()
    {
        // grab the various system properties
        osName = System.getProperty("os.name");
        osVersion = System.getProperty("os.version");
        osArch = System.getProperty("os.arch");
        javaVersion = System.getProperty("java.version");
        javaVendor = System.getProperty("java.vendor");

        // determine memory usage
        Runtime rtime = Runtime.getRuntime();
        freeMemory = rtime.freeMemory() / 1024;
        totalMemory = rtime.totalMemory() / 1024;
        usedMemory = totalMemory - freeMemory;
        maxMemory = rtime.maxMemory() / 1024;

        // determine video display information
        isHeadless = GraphicsEnvironment.isHeadless();
        if (!isHeadless) {
            try {
                GraphicsEnvironment env =
                    GraphicsEnvironment.getLocalGraphicsEnvironment();
                GraphicsDevice gd = env.getDefaultScreenDevice();
                DisplayMode mode = gd.getDisplayMode();
                bitDepth = mode.getBitDepth();
                refreshRate = mode.getRefreshRate() / 1024;
                isFullScreen = (gd.getFullScreenWindow() != null);
                displayWidth = mode.getWidth();
                displayHeight = mode.getHeight();

            } catch (Throwable t) {
                isHeadless = true;
            }
        }
    }

    /**
     * Returns a terse readable string representation of the operating
     * system name, version and architecture.
     */
    public String osToString ()
    {
        return osName + " (" + osVersion + "-" + osArch + ")";
    }

    /**
     * Returns a terse readable string representation of the java virtual
     * machine version and vendor.
     */
    public String jvmToString ()
    {
        return javaVersion + ", " + javaVendor;
    }

    /**
     * Returns a terse readable string representation of memory usage.
     */
    public String memoryToString ()
    {
        return freeMemory + "k free, " + usedMemory + "k used, " +
            totalMemory + "k total, " + maxMemory + "k max";
    }

    /**
     * Returns a terse readable string representation of the video display
     * settings.
     */
    public String videoToString ()
    {
        if (isHeadless) {
            return "headless or unavailable";
        }

        String sdepth = (bitDepth == -1) ? "unknown bit depth" :
            bitDepth + "-bit";
        String srate = (refreshRate == DisplayMode.REFRESH_RATE_UNKNOWN) ?
            "unknown refresh rate" : (refreshRate + "kHz");
        String sfull = (isFullScreen) ? "full-screen" : "windowed";
        return displayWidth + "x" + displayHeight + ", " + sdepth + ", " +
            srate + ", " + sfull;
    }

    @Override
    public String toString ()
    {
        StringBuilder buf = new StringBuilder();
        buf.append("OS: ").append(osToString()).append("\n");
        buf.append("JVM: ").append(jvmToString()).append("\n");
        buf.append("Memory: ").append(memoryToString()).append("\n");
        buf.append("Video: ").append(videoToString());
        return buf.toString();
    }
}