double numerus = 25;
double basis = Math.E;

// natural logarithm
double exponent = Math.log(numerus);
println("ln of 16 = " + exponent);

// reverse natural logarithm - "antilog"
double check = Math.pow(Math.E, exponent);
println("pow (E, exponent)  = " + check);



// 3rd root of 27
System.out.println( Math. pow( 27, 1.0/3.0 ) );

http://docs.oracle.com/javase/6/docs/api/java/lang/Math.html