📜  Java-数字类

📅  最后修改于: 2020-11-15 04:16:56             🧑  作者: Mango


通常,在使用Numbers时,我们使用原始数据类型,例如byte,int,long,double等。

int i = 5000;
float gpa = 13.65f;
double mask = 125;

但是,在开发过程中,我们遇到了需要使用对象而不是原始数据类型的情况。为了实现这一点,Java提供了包装器类

所有包装器类(Integer,Long,Byte,Double,Float,Short)都是抽象类Number的子类。

数字类

包装类的对象包含或包装其各自的原始数据类型。将原始数据类型转换为对象称为boxing ,编译器会注意这一点。因此,在使用包装器类时,您只需要将原始数据类型的值传递给Wrapper类的构造函数。

Wrapper对象将转换回原始数据类型,此过程称为拆箱。 Number类是java.lang包的一部分。

以下是装箱和拆箱的示例-

现场演示

public class Test {

   public static void main(String args[]) {
      Integer x = 5; // boxes int to an Integer object
      x =  x + 10;   // unboxes the Integer to a int
      System.out.println(x); 
   }
}

这将产生以下结果-

输出

15

为x分配整数值时,编译器将整数装箱,因为x是整数对象。以后,将x取消装箱,以便可以将它们添加为整数。

编号方法

以下是Number类的所有子类实现的实例方法的列表-

Sr.No. Method & Description
1 xxxValue()

Converts the value of this Number object to the xxx data type and returns it.

2 compareTo()

Compares this Number object to the argument.

3 equals()

Determines whether this number object is equal to the argument.

4 valueOf()

Returns an Integer object holding the value of the specified primitive.

5 toString()

Returns a String object representing the value of a specified int or Integer.

6 parseInt()

This method is used to get the primitive data type of a certain String.

7 abs()

Returns the absolute value of the argument.

8 ceil()

Returns the smallest integer that is greater than or equal to the argument. Returned as a double.

9 floor()

Returns the largest integer that is less than or equal to the argument. Returned as a double.

10 rint()

Returns the integer that is closest in value to the argument. Returned as a double.

11 round()

Returns the closest long or int, as indicated by the method’s return type to the argument.

12 min()

Returns the smaller of the two arguments.

13 max()

Returns the larger of the two arguments.

14 exp()

Returns the base of the natural logarithms, e, to the power of the argument.

15 log()

Returns the natural logarithm of the argument.

16 pow()

Returns the value of the first argument raised to the power of the second argument.

17 sqrt()

Returns the square root of the argument.

18 sin()

Returns the sine of the specified double value.

19 cos()

Returns the cosine of the specified double value.

20 tan()

Returns the tangent of the specified double value.

21 asin()

Returns the arcsine of the specified double value.

22 acos()

Returns the arccosine of the specified double value.

23 atan()

Returns the arctangent of the specified double value.

24 atan2()

Converts rectangular coordinates (x, y) to polar coordinate (r, theta) and returns theta.

25 toDegrees()

Converts the argument to degrees.

26 toRadians()

Converts the argument to radians.

27 random()

Returns a random number.

接下来是什么?

在下一节中,我们将介绍Java中的字符类。您将学习如何在Java中使用对象字符和原始数据类型char。