Java 系统相关参数获取

今天看lucene看到来源代码中有对操作系统和虚拟机方面的属性的工具类，特贴上以备后需。

package org.apache.lucene.util;

import java.lang.reflect.Field;
import java.util.StringTokenizer;


/**
 * Some useful constants.
 **/

public final class Constants {
  private Constants() {}  // can't construct

  /** JVM vendor info. */
  public static final String JVM_VENDOR = System.getProperty("java.vm.vendor");
  public static final String JVM_VERSION = System.getProperty("java.vm.version");
  public static final String JVM_NAME = System.getProperty("java.vm.name");
  public static final String JVM_SPEC_VERSION = System.getProperty("java.specification.version");

  /** The value of <tt>System.getProperty("java.version")</tt>. **/
  public static final String JAVA_VERSION = System.getProperty("java.version");
 
  /** The value of <tt>System.getProperty("os.name")</tt>. **/
  public static final String OS_NAME = System.getProperty("os.name");
  /** True iff running on Linux. */
  public static final boolean LINUX = OS_NAME.startsWith("Linux");
  /** True iff running on Windows. */
  public static final boolean WINDOWS = OS_NAME.startsWith("Windows");
  /** True iff running on SunOS. */
  public static final boolean SUN_OS = OS_NAME.startsWith("SunOS");
  /** True iff running on Mac OS X */
  public static final boolean MAC_OS_X = OS_NAME.startsWith("Mac OS X");
  /** True iff running on FreeBSD */
  public static final boolean FREE_BSD = OS_NAME.startsWith("FreeBSD");

  public static final String OS_ARCH = System.getProperty("os.arch");
  public static final String OS_VERSION = System.getProperty("os.version");
  public static final String JAVA_VENDOR = System.getProperty("java.vendor");
  
  private static final int JVM_MAJOR_VERSION;
  private static final int JVM_MINOR_VERSION;
 
  /** True iff running on a 64bit JVM */
  public static final boolean JRE_IS_64BIT;
  
  static {
    final StringTokenizer st = new StringTokenizer(JVM_SPEC_VERSION, ".");
    JVM_MAJOR_VERSION = Integer.parseInt(st.nextToken());
    if (st.hasMoreTokens()) {
      JVM_MINOR_VERSION = Integer.parseInt(st.nextToken());
    } else {
      JVM_MINOR_VERSION = 0;
    }
    boolean is64Bit = false;
    try {
      final Class<?> unsafeClass = Class.forName("sun.misc.Unsafe");
      final Field unsafeField = unsafeClass.getDeclaredField("theUnsafe");
      unsafeField.setAccessible(true);
      final Object unsafe = unsafeField.get(null);
      final int addressSize = ((Number) unsafeClass.getMethod("addressSize")
        .invoke(unsafe)).intValue();
      //System.out.println("Address size: " + addressSize);
      is64Bit = addressSize >= 8;
    } catch (Exception e) {
      final String x = System.getProperty("sun.arch.data.model");
      if (x != null) {
        is64Bit = x.indexOf("64") != -1;
      } else {
        if (OS_ARCH != null && OS_ARCH.indexOf("64") != -1) {
          is64Bit = true;
        } else {
          is64Bit = false;
        }
      }
    }
    JRE_IS_64BIT = is64Bit;
  }

  public static final boolean JRE_IS_MINIMUM_JAVA8 = JVM_MAJOR_VERSION > 1 || (JVM_MAJOR_VERSION == 1 && JVM_MINOR_VERSION >= 8);
  public static final boolean JRE_IS_MINIMUM_JAVA9 = JVM_MAJOR_VERSION > 1 || (JVM_MAJOR_VERSION == 1 && JVM_MINOR_VERSION >= 9);
 
}