java基础（一）---数据类型&Math方法&强制转换

 1 public class HelloWorld {
 2     public static void main(String args[]) {
 3         //各种数据类型的熟悉掌握，强制类型转换要看级别
 4         final int var = 100;
 5         int varr = 200;
 6         float m = -21.5f;
 7         double p = 21.234;
 8         boolean judge = true;
 9         char ch = ‘a‘;
10         long num = 625;
11         short num1 = 12;
12         byte a = 1;
13         String str = "I am a great boy!";
14         
15         //算术运算依赖Math类各种静态方法
16         System.out.println(Math.abs(m));    //绝对值
17         System.out.println(Math.sin(a));        //三角函数
18         System.out.println(Math.asin(0.5));//反三角函数
19         System.out.println(Math.sqrt(var));//开平方跟
20         System.out.println(Math.cbrt(num));//开立方根
21         System.out.println(Math.round(m));//四舍五入
22         System.out.println(Math.ceil(1.5));//向上取整
23         System.out.println(Math.floor(1.9));//向下取整
24         System.out.println(Math.max(100, 50));//取大值
25         System.out.println(Math.min(12.3, 13.3));//取小值
26         System.out.println(Math.random()+1);//生成随机数
27         System.out.println(Math.pow(2, 10));//指数运算：计算        
28 a(前者)的b(后者)次幂
29         System.out.println(Math.log10(100));//对数运算
30     }
31 }        
//以上代码eclipse编译通过