Number & Math 类-java

Java Number & Math class
development process, we will meet applicable object rather than the case of built-in data types. To solve this problem, Java language provides a corresponding wrapper class for each built-in data types.
Integer, Long, Byte, Double, Float, Short abstract classes are subclasses of Number.

• Java Math
• Number & Math methods

Special support by the compiler package to be packing, so when the built-in data types are treated as objects used, the compiler will it as a built-in type packing wrapper class, the compiler can also put a target for the unpacking built-in objects. Number java.lang class data packet.

Examples

public class Test{

   public static void main(String args[]){
      Integer x = 5;
      x =  x + 10;
      System.out.println(x); 
   }
}

 

Java Math

It contains the properties and methods used to perform basic mathematical operations, like ever exponential, logarithmic, trigonometric functions and square root.
Math methods are defined as static in the form of the function can be called directly by the main math class.

 

public class Test {  
    public static void main (String []args)  
    {  
        System.out.println("90 度的正弦值：" + Math.sin(Math.PI/2));  
        System.out.println("0度的余弦值：" + Math.cos(0));  
        System.out.println("60度的正切值：" + Math.tan(Math.PI/3));  
        System.out.println("1的反正切值： " + Math.atan(1));  
        System.out.println("π/2的角度值：" + Math.toDegrees(Math.PI/2));  
        System.out.println(Math.PI);  
    }  
}

Number & Math methods

 

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Numbering	Methods and description
1	xxxValue () converts the value XXX Number object data type and returns
2	the compareTo () will be compared with parameters of the object number
3	equals () is determined number
4	valueOf () Returns a specified Number object built-in data types
5	toString () Returns a string value
6	the parseInt () parse a string of type int
7	ABS () returns the absolute value of the parameter
8	ceil () Returns greater than or equal to (> =) to a given parameter smallest integer, double precision floating-type
9	floor () returns is less than or equal to (<=) the largest integer given parameter
10	RINT () returns the nearest integer parameters. Return type is double
11	round () rounding, Math.floor (x + 0.5), plus the original digital round down 0.5
12	min () returns the minimum of the two parameters
13	max () Returns the maximum value of the two parameters
14	exp () Returns the number of parameters of power base e of natural
15	log () to return the value of the parameters of the natural logarithm base
16	POW () returns the first parameter the second parameter th
17	sqrt () request parameter square root
18	sin () Sine the parameter value of the specified type double
19	cos () request type parameter specifies the cosine double
20	Tan () request tangent type parameter specifies double
21	asin () request to specify the parameters of the type double arcsine
22	ACOS () request type parameter specifies double arccosine
23	ATN () request type parameter specifies double arctangent
24	atn2 () to Cartesian coordinates to polar coordinates, polar coordinates and returns the value of the angle
25	toDergrees () converts the parameter to an angle
26	toRadians () will be converted to an angle in radians
27	random() 返回一个随机数

示例:floor,round和ceil

public class Main {   
  public static void main(String[] args) {   
    double[] nums = { 1.4, 1.5, 1.6, -1.4, -1.5, -1.6 };   
    for (double num : nums) {   
      test(num);   
    }   
  }   

  private static void test(double num) {   
    System.out.println("Math.floor(" + num + ")=" + Math.floor(num));   
    System.out.println("Math.round(" + num + ")=" + Math.round(num));   
    System.out.println("Math.ceil(" + num + ")=" + Math.ceil(num));   
  }   
}