# Java Pi

Programming is used to solve real-life problems that may include implementing different mathematical formulas. And these formulas are used in various mathematical constants and functions.

### What is Pi?

The Pi is a constant value used in different formulas in geometry like calculating circumference, area, volume, etc. It is a mathematical constant that is defined as the circumference of a circle divided by its diameter.

The value of a constant pi is approximately 3.14. Java provides built-in constant field of Pi that belong to java.lang,Math class.

The following program shows the use of constant value pi without using the built-in constant field.

SamplePi.java

Output:

```Radius of circle: 5
Area of circle is: 78.5
Circumference of circle is: 31.400000000000002
```

In the above code, the pi value is set to 3.14 using a final double variable pi. And the area and circumference are calculated and displayed.

### Pi in Java

The Java Math class provides methods for implementing numeric operations like logarithm, square root, trigonometric functions, minimum or maximum number.

The pi is a field defined in the Math class as a static variable of type double. To access this constant the Java program has to import java.lang.Math class. As it's a static variable we can directly access it using the Math.PI into the Java program.

The following program shows the use of Math.PI variable in a Java program.

SamplePi2.java

Output:

```Radius of circle: 5
Area of circle is: 78.53981633974483
Circumference of circle is: 31.41592653589793
```

In the above code, the Math.PI is used instead of declaring a local variable. And the area and circumference of the circle is displayed on the console.

### Program for calculating the volume of a cylinder using built-in variable and user-defined variable

SamplePi3.java

Output:

```Volume of cylinder by using built-in variable PI is: 1178.0972450961724
Volume of cylinder by using the user-defined Pi value is: 1177.5
```

The above Java code demonstrates both the ways of using Pi constant in a program. The area of a cylinder is calculated using multiplication operation and displayed using both methods.

In this article, we have discussed the mathematical constant Pi, how it can be implemented in a Java program and a program to demonstrate it.

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