Java By Example: Constants

Java supports constants of character, string, boolean, and numeric values.

import java.lang.Math;
import java.math.BigDecimal;

class Main {
  public static void main(String[] args) {

    // 'final' declares a constant value.
    final String s = "constant";
    System.out.println(s);

    // A `final` statement can appear before Data Type.
    final Integer n = 500000000;

    // A numeric constant has type usually declared by user.
    final Double d = 3e+20 / n;
    System.out.println(d);

    // To convert a numeric constant type
    // It is required to cast to `BigDecimal` first
    // Then cast to other data types (like `BigInteger`)
    final BigDecimal e = new BigDecimal(d);
    System.out.println(e.toBigInteger());

    System.out.println(Math.sin(d));
  }
}

javac Constants.java
java Constants
# constant
# 6e+11
# 600000000000
# -0.28470407323754404

Reference:
BigDecimal Class in Java - GeeksforGeeks
is there anyway to convert from Double to BigInteger? – Java (tutorialink.com)