How do I get the PI value?

The number π is a mathematical constant, the ratio of a circle’s circumference to its diameter, commonly approximated as 3.14159. It has been represented by the Greek letter “π” since the mid-18th century, though it is also sometimes spelled out as “pi” (/paɪ/).

From: Wikipedia

The code snippet below show you how to obtain the PI value in Java. We use the Math.PI static field to get the value of PI.

package org.kodejava.example.math;

public class GetPiExample {
    public static void main(String[] args) {
        // The PI value represented by Math.PI
        System.out.println("PI = " + Math.PI);

        // Using the Math.PI to calculate area of a circle.
        double radius = 8;
        double circleArea = Math.PI * Math.pow(radius, 2);
        System.out.println("Circle Area = " + circleArea);
    }
}

Here is the program output:

PI = 3.141592653589793
Circle Area = 201.06192982974676

How do I get the minimum or maximum value between two numbers?

The code below show you how to use the Math.min() and Math.max() method call the get the minimum and maximum value between two numbers. As other method in the Math class these methods also overloaded to accept many types of primitive data.

package org.kodejava.example.math;

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

        Double value1 = 100.0D;
        Double value2 = 200.0D;

        double max1 = Math.max(value1, value2);
        double min1 = Math.min(value1, value2);

        float max2 = Math.max(value1.floatValue(), value2.floatValue());
        float min2 = Math.min(value1.floatValue(), value2.floatValue());

        int max3 = Math.max(value1.intValue(), value2.intValue());
        int min3 = Math.min(value1.intValue(), value2.intValue());

        long max4 = Math.max(value1.longValue(), value2.longValue());
        long min4 = Math.min(value1.longValue(), value2.longValue());

        System.out.println("Max value in double: " + max1);
        System.out.println("Min value in double: " + min1);
        System.out.println("Max value in float : " + max2);
        System.out.println("Min value in float : " + min2);
        System.out.println("Max value in int   : " + max3);
        System.out.println("Min value in int   : " + min3);
        System.out.println("Max value in long  : " + max4);
        System.out.println("Min value in long  : " + min4);
    }
}

The result of the above program are:

Max value in double: 200.0
Min value in double: 100.0
Max value in float : 200.0
Min value in float : 100.0
Max value in int   : 200
Min value in int   : 100
Max value in long  : 200
Min value in long  : 100

How do I get the absolute value of a number?

The example below show you how to get the absolute value of a number. To get the absolute value or the abs value of a number we use the Math.abs() method call. The Math.abs() method is an overloaded that can accept value in type of double, float, int or long.

package org.kodejava.example.math;

public class GetAbsoluteValueExample {
    public static void main(String[] args) {
        Double value = -10.0D;

        double abs1 = Math.abs(value);
        System.out.println("Absolute value in double: " + abs1);

        float abs2 = Math.abs(value.floatValue());
        System.out.println("Absolute value in float : " + abs2);

        int abs3 = Math.abs(value.intValue());
        System.out.println("Absolute value in int   : " + abs3);

        long abs4 = Math.abs(value.longValue());
        System.out.println("Absolute value in long  : " + abs4);
    }
}

The code snippet above print the following result:

Absolute value in double: 10.0
Absolute value in float : 10.0
Absolute value in int   : 10
Absolute value in long  : 10

How do I convert BigInteger into another radix number?

In this example you’ll see how we can convert a java.math.BigInteger number into another radix such as binary, octal and hexadecimal.

package org.kodejava.example.math;

import java.math.BigInteger;

public class BigIntegerConversion {
    public static void main(String[] args) {
        BigInteger number = new BigInteger("2017");

        System.out.println("Number      = " + number);
        System.out.println("Binary      = " + number.toString(2));
        System.out.println("Octal       = " + number.toString(8));
        System.out.println("Hexadecimal = " + number.toString(16));

        number = new BigInteger("FF", 16);
        System.out.println("Number      = " + number);
        System.out.println("Number      = " + number.toString(16));
    }
}

The result of our examples:

Number      = 2017
Binary      = 11111100001
Octal       = 3741
Hexadecimal = 7e1
Number      = 255
Number      = ff

How do I do math operation for BigDecimal?

package org.kodejava.example.math;

import java.math.BigDecimal;
import java.math.RoundingMode;

public class BigDecimalOperation {
    public static void main(String[] args) {
        BigDecimal decimalA = new BigDecimal("98765432123456789");
        BigDecimal decimalB = new BigDecimal("10");

        decimalA = decimalA.add(decimalB);
        System.out.println("decimalA = " + decimalA);

        decimalA = decimalA.multiply(decimalB);
        System.out.println("decimalA = " + decimalA);

        decimalA = decimalA.subtract(decimalB);
        System.out.println("decimalA = " + decimalA);

        decimalA = decimalA.divide(decimalB, RoundingMode.DOWN);
        System.out.println("decimalA = " + decimalA);

        decimalA = decimalA.pow(2);
        System.out.println("decimalA = " + decimalA);

        decimalA = decimalA.negate();
        System.out.println("decimalA = " + decimalA);
    }
}

Our code snippet results are:

decimalA = 98765432123456799
decimalA = 987654321234567990
decimalA = 987654321234567980
decimalA = 98765432123456798
decimalA = 9754610582533151990855052972412804
decimalA = -9754610582533151990855052972412804

How do I do math operation for BigInteger?

package org.kodejava.example.math;

import java.math.BigInteger;

public class BigIntegerOperation {
    public static void main(String[] args) {
        BigInteger numberA = new BigInteger("98765432123456789");
        BigInteger numberB = BigInteger.TEN;

        numberA = numberA.add(numberB);
        System.out.println("numberA = " + numberA);

        numberA = numberA.multiply(numberB);
        System.out.println("numberA = " + numberA);

        numberA = numberA.subtract(numberB);
        System.out.println("numberA = " + numberA);

        numberA = numberA.divide(numberB);
        System.out.println("numberA = " + numberA);

        numberA = numberA.mod(numberB);
        System.out.println("numberA = " + numberA);

        numberA = numberA.pow(2);
        System.out.println("numberA = " + numberA);

        numberA = numberA.negate();
        System.out.println("numberA = " + numberA);
    }
}

Our class result are:

numberA = 98765432123456799
numberA = 987654321234567990
numberA = 987654321234567980
numberA = 98765432123456798
numberA = 8
numberA = 64
numberA = -64