Home » Core Java » Pi in Java Example Mary has graduated from Mechanical Engineering department at ShangHai JiaoTong University. She also holds a Master degree in Computer Science from Webster University. During her studies she has been involved with a large number of projects ranging from programming and software engineering. She works as a senior Software Engineer in the telecommunications sector where she acts as a leader and works with others to design, implement, and monitor the software solution.

# Pi in Java Example

In this post, we feature a comprehensive article about Pi in Java.

## 1. Introduction

PI is a mathematics number defined as the circumference of any circle divided by its diameter. Java has provided the java.lang.Math class since version 1. It includes a static constant `PI` with value of `3.141592653589793`.

```/*the double value that is closer than any other to pi, the ratio of the circumference of a circle to its diameter.*/
static double PI = 3.141592653589793;```

In this example, I will print out the `Math.PI` value and use it to calculate a circle’s circumference and area.

## 2. Technologies Used

• Java 11
• Maven 3.3.9
• Eclipse Oxygen
• Junit 4.12

## 3. Maven Project

### 3.1 Dependencies

I will include `Junit` in the `pom.xml`.

pom.xml

```<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>jcg.zheng.demo</groupId>
<artifactId>java-pi-demo</artifactId>
<version>0.0.1-SNAPSHOT</version>
<build>
<sourceDirectory>src</sourceDirectory>
<plugins>
<plugin>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.8.0</version>
<configuration>
<release>11</release>
</configuration>
</plugin>
</plugins>
</build>
<dependencies>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.12</version>
</dependency>
</dependencies>
</project>```

### 3.2 Circle

In this step, I will create a `Circle` class which has a diameter data member and two methods:

• `calculateCircumference()` – calculate a circle’s circumference by multiplying PI by its diameter.
• `calculateArea`() – calculate a circle’s area by multiplying PI by the square of its radius.

Circle.java

```package jcg.zheng.demo;

public class Circle {

public Circle(double diameter) {
super();
this.diameter = diameter;
}

private double diameter;

public double calculateCircumference() {
return Math.PI * diameter;
}

public double calculateArea() {
return Math.PI * Math.pow(diameter / 2, 2);
}
}
```

### 3.3. Circle Test

In this step, I will create a `CircleTest` class to print out `Math.PI` value and calculate a circle’s circumference and area.

• `print_Pi_value()` – prints out `Math.PI` value.
• `calculateCircumference()` – calculates the circumference of a circle whose diameter is 10 units.
• `calculateArea()` – calculates the area of a circle whose diameter is 20 units.

CircleTest.java

```package jcg.zheng.demo;

import static org.junit.Assert.assertEquals;

import org.junit.Test;

public class CircleTest {

@Test
public void print_Pi_value() {
System.out.println(Math.PI);
System.out.printf("%.16f", Math.PI);

assertEquals(3.14, Math.PI, 2);
}

@Test
public void calculateCircumference() {
double diameter = 10;
Circle c = new Circle(diameter);

assertEquals(31.42, c.calculateCircumference(), 2);
}

@Test
public void calculateArea() {
double diameter = 20;
Circle c = new Circle(diameter);

assertEquals(314.23, c.calculateArea(), 2);
}
}
```

Execute `mvn test -Dtest=CircleTest` and capture output here.

Output

```-------------------------------------------------------
T E S T S
-------------------------------------------------------
Running jcg.zheng.demo.CircleTest
3.141592653589793
3.1415926535897930
Tests run: 3, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.126 sec

Results :

Tests run: 3, Failures: 0, Errors: 0, Skipped: 0```

Note: `Math.PI` value is defined as 3.141592653589793.

## 4. Pi in Java – Summary

In this example, I demonstrate the `Math.PI` value and how to use it to calculate a circle’s circumference and area.

This example consists of a Maven project which demonstrates the `Math.PI` constant.

You can download the full source code of this example here: Pi in Java Example

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