The Numbers Classes数字类

When working with numbers, most of the time you use the primitive types in your code.在处理数字时，大多数情况下都会在代码中使用基本类型。For example:例如：

int i = 500;
float gpa = 3.65f;
byte mask = 0x7f;

There are, however, reasons to use objects in place of primitives, and the Java platform provides wrapper classes for each of the primitive data types.然而，使用对象代替原语是有原因的，Java平台为每种原语数据类型提供了包装类。These classes "wrap" the primitive in an object.这些类将原语“包装”到对象中。Often, the wrapping is done by the compiler—if you use a primitive where an object is expected, the compiler boxes the primitive in its wrapper class for you.通常，包装是由编译器完成的—如果在需要对象的位置使用原语，编译器会将原语装箱到其包装类中。Similarly, if you use a number object when a primitive is expected, the compiler unboxes the object for you.类似地，如果在需要原语时使用数字对象，编译器将为您拆箱该对象。For more information, see Autoboxing and Unboxing有关详细信息，请参阅自动装箱和拆箱。

All of the numeric wrapper classes are subclasses of the abstract class Number:所有数字包装类都是抽象类Number的子类：

There are three reasons that you might use a Number object rather than a primitive:使用Number对象而不是原语有三个原因：

1. As an argument of a method that expects an object (often used when manipulating collections of numbers).作为期望对象的方法的参数（通常在处理数字集合时使用）。
2. To use constants defined by the class, such as MIN_VALUE and MAX_VALUE, that provide the upper and lower bounds of the data type.使用类定义的常量，例如提供数据类型上限和下限的MIN_VALUE和MAX_VALUE。
3. To use class methods for converting values to and from other primitive types, for converting to and from strings, and for converting between number systems (decimal, octal, hexadecimal, binary).使用类方法将值与其他基元类型进行转换，将值与字符串进行转换，并在数字系统（十进制、八进制、十六进制、二进制）之间进行转换。

The following table lists the instance methods that all the subclasses of the Number class implement.下表列出了Number类的所有子类实现的实例方法。

Each Number class contains other methods that are useful for converting numbers to and from strings and for converting between number systems.每个Number类都包含其他方法，这些方法对于在字符串之间转换数字以及在数字系统之间转换数字非常有用。The following table lists these methods in the Integer class.下表列出了Integer类中的这些方法。Methods for the other Number subclasses are similar:其他Number子类的方法类似：