더쿨라이프

Java의 정규표현식에서 \와 $ 사용할 때, 오류 발생할 수 있습니다.

이런 문제점을 보완하기 위해서는 quoteReplacement()를 사용할 수 있습니다.

예제1: test.replaceAll(Matcher.quoteReplacement("\\"), "/");

예제2: test.replaceAll("/", Matcher.quoteReplacement("\\"));

• quoteReplacement

  public static String quoteReplacement(String s)

  Returns a literal replacement String for the specified String. This method produces a String that will work as a literal replacement s in the appendReplacement method of the Matcher class. The String produced will match the sequence of characters in s treated as a literal sequence. Slashes ('\') and dollar signs ('$') will be given no special meaning.

  Parameters:

  s - The string to be literalized

  Returns:

  A literal string replacement

  Since:

  1.5

출처 : http://docs.oracle.com/javase/7/docs/api/java/util/regex/Matcher.html#quoteReplacement(java.lang.String)

In mathematics, the root mean square (abbreviated RMS or rms), also known as the quadratic mean, is a statistical measure of the magnitude of a varying quantity. It is especially useful when variates are positive and negative, e.g., sinusoids. In the field of electrical engineering, the effective (RMS) value of a periodic current is equal to the DC voltage that delivers the same average power to a resistor as the periodic current.^[1]

It can be calculated for a series of discrete values or for a continuously varying function. Its name comes from its definition as the square root of the meanof the squares of the values. It is a special case of the generalized mean with the exponent p = 2.

Definition[edit]

The RMS value of a set of values (or a continuous-time waveform) is the square root of the arithmetic mean (average) of the squares of the original values (or the square of the function that defines the continuous waveform).

In the case of a set of n values , the RMS

The corresponding formula for a continuous function (or waveform) f(t) defined over the interval  is

and the RMS for a function over all time is

The RMS over all time of a periodic function is equal to the RMS of one period of the function. The RMS value of a continuous function or signal can be approximated by taking the RMS of a series of equally spaced samples. Additionally, the RMS value of various waveforms can also be determined withoutcalculus, as shown by Cartwright.^[2]

In the case of the RMS statistic of a random process, the expected value is used instead of the mean.

(출처: http://en.wikipedia.org/wiki/Root_mean_square)