Java - Numbers Class 数值类
2019-05-22 本文已影响0人
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Java - Numbers Class
Number Methods
| NO. | Method && Description |
|---|---|
| 1 | xxxValue()<br />转换为指定类型的值 |
| 2 | compareTo()<br />比较值的大小 |
| 3 | equals()<br />判断大小 |
| 4 | valueOf()<br />返回一个整数对象并且持有指定的值 |
| 5 | toString()<br />返回一个字符串对象代表当前指定的int or integer |
| 6 | parseInt()<br />方法用于格式化一些字符串返回整数 |
| 7 | abs()<br />求绝对值 |
| 8 | ceil()<br />向上取整 , 返回double |
| 9 | floor()<br />向下取整, 返回 double |
| 10 | rint()<br />四舍五入取整数，返回double |
| 11 | round()<br />四舍五入 |
| 12 | min()<br />取最小值 |
| 13 | max()<br />取最大值 |
| 14 | exp()<br />对数e的计算 |
| 15 | log()<br />返回自然的对数 |
| 16 | pow()<br />阶运算，第一个参数做底数，第二参数做阶数 |
| 17 | sqrt()<br />获取平方根 |
| 18 | sin()<br />正弦 |
| 19 | cos()<br />余弦 |
| 20 | tan()<br />正切 |
| 21 | asin()<br />反正弦 |
| 22 | acos()<br />反余弦 |
| 23 | atan()<br />反正切 |
| 24 | atan2()<br />直角坐标转换为极坐标 |
| 25 | toDegrees()<br />转换为角度 |
| 26 | toRadians()<br />转换为弧度 |
| 27 | random()<br />随机数 |
Example
public class Methods {
public static void main(String[] args) {
Integer x = 8;
// XXXValue()
System.out.println("Number.xxxValue()");
// return byte primitive data type
System.out.println(x.byteValue());
// return double primitive data type
System.out.println(x.doubleValue());
// return long primitive data type
System.out.println(x.longValue());
// compareTo();
System.out.println("Number.compareTo()");
// return 1
System.out.println(x.compareTo(6));
// return 0
System.out.println(x.compareTo(8));
// return -1
System.out.println(x.compareTo(10));
// equals()
System.out.println("Number.equals()");
Integer y = 8;
Integer z = 9;
short h = 8;
String m = "8";
System.out.println(x.equals(y));
System.out.println(x.equals(z));
System.out.println(x.equals(h));
System.out.println(x.equals(m));
// valueOf()
System.out.println("Number.valueOf()");
System.out.println(Double.valueOf("99"));
System.out.println(Float.valueOf("90"));
System.out.println(Long.valueOf("999"));
System.out.println(Integer.valueOf("9", 16));
// toString
System.out.println("Number.toString()");
String s1 = Integer.toString(8);
System.out.println(s1 instanceof String);
// parseInt()
System.out.println("parseInt()");
System.out.println(Integer.parseInt("666"));
System.out.println(Double.parseDouble("888"));
System.out.println(Float.parseFloat("777"));
// abs()
System.out.println("Math.abs()");
System.out.println(Math.abs(Integer.parseInt("-99")));
System.out.println(Math.abs(Double.parseDouble("-88.88")));
// ceil() return double type
double d1 = -100.81;
float f1 = 99;
System.out.println("Math.ceil()");
System.out.println(Math.ceil(d1));
System.out.println(Math.ceil(f1));
// floor()
System.out.println("Math.floor()");
System.out.println(Math.floor(-99.99));
System.out.println(Math.floor(88.10));
// rint()
System.out.println("Math.rint()");
System.out.println(Math.rint(99.1));
System.out.println(Math.rint(99.5));
System.out.println(Math.rint(99.6));
// round()
System.out.println("Math.round()");
System.out.println(Math.round(99.1));
System.out.println(Math.round(99.9));
// min()
System.out.println("Math.min()");
System.out.println(Math.min(11, 44.1));
// max()
System.out.println("Math.max()");
System.out.println(Math.max(11, 44.1));
// exp() 对数
System.out.println("Math.exp()");
System.out.println(Math.E);
System.out.println(Math.exp(2));
// log()
System.out.println("Math.log()");
System.out.println(Math.log(7.39));
// pow
System.out.println("Math.pow");
System.out.println(Math.pow(2, 5));
// sqrt
System.out.println("Math.sqrt");
System.out.println(Math.sqrt(2));
// sin
double degrees = 60.0;
double radians = Math.toRadians(degrees);
System.out.println("Math.sin()");
System.out.println(radians);
System.out.println(Math.sin(radians));
System.out.println(Math.sqrt(3) / 2);
// cos
System.out.println("Math.cos()");
System.out.println(Math.cos(radians));
// tan
System.out.println("Math.tan()");
System.out.println(Math.tan(radians));
// asin
System.out.println("Math.asin()");
System.out.println(Math.asin(Math.sin(radians)) == radians);
// acos
System.out.println("Math.acos()");
System.out.println(Math.acos(Math.cos(radians)) == radians);
// atan
System.out.println("Math.atan()");
System.out.println(Math.atan(Math.tan(radians)) == radians);
// atan2
System.out.println("Math.atan2()");
System.out.println(Math.atan2(30, 45));
//toDegrees
System.out.println("Math.toDegrees()");
System.out.println(Math.round(Math.toDegrees(radians)));
//toRadians
System.out.println("Math.toRadians()");
System.out.println(Math.toRadians(degrees));
//random
System.out.println("Math.random()");
System.out.println(Math.round(Math.random() * 1000 + 1));
}
}
Output
Number.xxxValue()
8
8.0
8
Number.compareTo()
1
0
-1
Number.equals()
true
false
false
false
Number.valueOf()
99.0
90.0
999
9
Number.toString()
true
parseInt()
666
888.0
777.0
Math.abs()
99
88.88
Math.ceil()
-100.0
99.0
Math.floor()
-100.0
88.0
Math.rint()
99.0
100.0
100.0
Math.round()
99
100
Math.min()
11.0
Math.max()
44.1
Math.exp()
2.718281828459045
7.38905609893065
Math.log()
2.0001277349601105
Math.pow
32.0
Math.sqrt
1.4142135623730951
Math.sin()
1.0471975511965976
0.8660254037844386
0.8660254037844386
Math.cos()
0.5000000000000001
Math.tan()
1.7320508075688767
Math.asin()
true
Math.acos()
true
Math.atan()
true
Math.atan2()
0.5880026035475675
Math.toDegrees()
60
Math.toRadians()
1.0471975511965976
Math.random()
199
