Java's Math class contains methods and constants that support mathematical computation. : Math class « Utility Classes « SCJP

1. SCJP
2. Utility Classes
3. Math class

Math class is declared final, so you cannot extend it. 
Constructor of Math class is private, so you cannot create an instance. 
Methods and constants from Math class are static, 

public class MainClass{
 public static void main(String args[]) {
  System.out.println(Math.E);
  System.out.println(Math.PI);
  System.out.println(Math.abs(-1234));
  System.out.println(Math.cos(Math.PI/4));
  System.out.println(Math.sin(Math.PI/2));
  System.out.println(Math.tan(Math.PI/4));
  System.out.println(Math.log(1));
  System.out.println(Math.exp(Math.PI));
  for(int i=0;i<3;++i)
   System.out.print(Math.random()+" ");
  System.out.println();
 }
}

2.718281828459045
3.141592653589793
1234
0.7071067811865476
1.0
0.9999999999999999
0.0
23.140692632779267
0.05110563295004433 0.6168577584907208 0.19441074013526116