Summary of Numbers - Java Tutorial 5.0 英文版

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Summary of Numbers

You use an instance of one of the Number classes — Byte, Double, Float, Integer, Long, and Short — to contain a number of primitive type. You can also use BigInteger and BigDecimal for arbitrary-precision numbers.

The Number classes include class methods and constants, which are useful in a variety of ways. The MIN_VALUE and MAX_VALUE constants contain the smallest and largest values that can be contained by an object of that type. The byteValue, shortValue, and similar methods convert one numeric type to another. The valueOf method converts a string to a number, and the toString method converts a number to a string.

To format a number to display to an end user, you use the NumberFormat class in the java.text package. When using NumberFormat, you can get a default format for decimal numbers, percentages, or currency. Or, you can design a custom format using patterns. If you are using JDK 5.0 or later, the printf facility provides yet another means for formatting your output.

The Math class contains a variety of class methods for performing mathematical functions. This class includes the trigonometric functions, such as computing sine, cosine, and so on. Math also includes functions for logarithm calculations, as well as basic arithmetic functions, such as rounding. Finally, Math contains a method, random, for generating random numbers.

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