public class Test3 {
    public static void main(String[] args) {
        String[] a = new String[] { "aaa", "aaa", "ccc" };
        String[] b = new String[] { "aaa", "bbb", "ccc" };
        Clock clock = Clock.getClock();
        long start = System.nanoTime(); // 获取开始时间
        System.out.println(equals(a,b));
        long end = System.nanoTime(); // 获取结束时间
        clock.stopAndPrint("耗时:");
        System.out.println(end + "===" + start);
    }
    //比较两个string[] 无序是否相等
    public static boolean equals(String a[],String b[]){
           if(a.length!=b.length) return false;
           ].hashCode()^b[].hashCode();
           ;i<a.length;i++){
                n^=a[i].hashCode()^b[i].hashCode();
          }
           ) return true;
             return false;
        }
}  

/**
     * Returns the current value of the most precise available system
     * timer, in nanoseconds.
     *
     * <p>This method can only be used to measure elapsed time and is
     * not related to any other notion of system or wall-clock time.
     * The value returned represents nanoseconds since some fixed but
     * arbitrary time (perhaps in the future, so values may be
     * negative).  This method provides nanosecond precision, but not
     * necessarily nanosecond accuracy. No guarantees are made about
     * how frequently values change. Differences in successive calls
     * that span greater than approximately 292 years (2<sup>63</sup>
     * nanoseconds) will not accurately compute elapsed time due to
     * numerical overflow.
     *
     * <p> For example, to measure how long some code takes to execute:
     * <pre>
     *   long startTime = System.nanoTime();
     *   // ... the code being measured ...
     *   long estimatedTime = System.nanoTime() - startTime;
     * </pre>
     *
     * @return The current value of the system timer, in nanoseconds.
     * @since 1.5
     */

long currentTime = System.currentTimeMillis();

SimpleDateFormat formatter = new SimpleDateFormat("yyyy年-MM月dd日-HH时mm分ss秒");

Date date = new Date(currentTime);

System.out.println(formatter.format(date));

当前时间:2011年-08月10日-14时11分46秒
另：
可获得当前的系统和用户属性：
       String osName = System.getProperty(“os.name”);
　　String user = System.getProperty(“user.name”);
　　System.out.println(“当前操作系统是：” + osName);
　　System.out.println(“当前用户是：” + user);
       System.getProperty 这个方法可以得到很多系统的属性。

 /**
     * Returns the current time in milliseconds.  Note that
     * while the unit of time of the return value is a millisecond,
     * the granularity of the value depends on the underlying
     * operating system and may be larger.  For example, many
     * operating systems measure time in units of tens of
     * milliseconds.
     *
     * <p> See the description of the class <code>Date</code> for
     * a discussion of slight discrepancies that may arise between
     * "computer time" and coordinated universal time (UTC).
     *
     * @return  the difference, measured in milliseconds, between
     *          the current time and midnight, January 1, 1970 UTC.
     * @see     java.util.Date
     */