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Math constants

Learn built-in constants like Math.PI.

Math constants

Java's Math class provides mathematical constants and methods. The best-known constants are Math.PI (the number pi) and Math.E (the number e). These constants are static final and can be used directly.

Example: double area = Math.PI * radius * radius;. Here Math.PI gives the number pi; approximately 3.14159. It is used to calculate a circle's area. Math.E is the natural logarithm base; approximately 2.71828. You do not need to define these constants yourself; the Math class provides them ready. Math also contains methods like abs, max and sqrt; these are static and called through the class name.

Math methods

The Math class also provides mathematical methods: Math.abs for absolute value, Math.max for the largest, Math.sqrt for square root. All are static and called through the class name.

Example: int absVal = Math.abs(-5); returns five. int big = Math.max(3, 7); returns seven. double root = Math.sqrt(16); returns four. These methods are called as Math.methodName(...) without an instance. The Math class's constructor is hidden; new Math() cannot be written. All members are static. This is the typical design of utility classes.

Practice Use Math constants and methods

In a main method calculate a circle's area. Write double radius = 5.0. Calculate the area with double area = Math.PI * radius * radius;. Get the absolute value with int absVal = Math.abs(-10);. Print the area and absVal values on separate lines.

Starter code

Main.java
// Use Math in main
// Calculate circle area and absolute value
// Print results

Sample solution

Main.java
public class Main {
    public static void main(String[] args) {
        double radius = 5.0;
        double area = Math.PI * radius * radius;
        int absVal = Math.abs(-10);
        System.out.println(area);
        System.out.println(absVal);
    }
}

Expected output

78.53981633974483
10

Questions and answers

Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.

1 Which constant is used for a circle's area?

  • Math.PI Correct answer
  • Math.E
  • Math.AREA
  • Math.RADIUS

Explanation: Math.PI gives the number pi; it is used in circle area.

2 Complete the Math.abs call

Question 
int result = ____;
Answer 
int result = Math.abs(-5);

Explanation: Math.abs gives the absolute value.

3 Match Math members

Term Meaning
Math.abs Absolute value
Math.max Largest
Math.sqrt Square root
Math.PI Pi number

All lessons in Intermediate

1 Classes

  1. class
  2. Attributes
  3. Methods
  4. new
  5. toString
  6. Summary - Classes

2 Constructor

  1. Constructor basics
  2. Parameterized constructor
  3. Constructor overloading
  4. this()
  5. Default constructor
  6. Summary - Constructor

3 Inheritance

  1. extends
  2. super
  3. Method overriding
  4. Object class
  5. final class and method
  6. Summary - Inheritance

4 Project: Library

  1. Class design
  2. Book model
  3. Member management
  4. Borrow flow
  5. Putting it together

5 Encapsulation

  1. private fields
  2. Getter
  3. Setter
  4. Package-private
  5. Record
  6. Summary - Encapsulation

6 Static

  1. static fields
  2. static methods
  3. static block
  4. Class variables
  5. instanceof
  6. Summary - Static

7 Constants

  1. static final
  2. Uppercase convention
  3. Constants with enum
  4. Interface constants
  5. Math constants
  6. Summary - Constants

8 Project: Quiz app

  1. Quiz model
  2. Adding questions
  3. Running the quiz
  4. Score calculation
  5. Putting it together

9 Interface

  1. interface
  2. implements
  3. default methods
  4. static methods
  5. Multiple interfaces
  6. Summary - Interface

10 Abstract class

  1. abstract class
  2. abstract methods
  3. Abstract and concrete
  4. Abstract vs interface
  5. Sealed class
  6. Summary - Abstract class

11 Polymorphism

  1. Polymorphism basics
  2. Dynamic binding
  3. Override rules
  4. Abstract reference
  5. Pattern matching
  6. Summary - Polymorphism

12 Project: Blog app

  1. Model design
  2. Blog class
  3. Adding comments
  4. Search and filter
  5. Putting it together

13 File I/O

  1. File class
  2. FileReader and FileWriter
  3. BufferedReader
  4. PrintWriter
  5. try-with-resources
  6. Summary - File I/O

14 Serialization

  1. Jackson ObjectMapper
  2. readValue
  3. writeValueAsString
  4. JsonProperty
  5. List and Map serialization
  6. Summary - Serialization

15 Generics

  1. Generic class
  2. Generic method
  3. Bounded type
  4. Wildcard
  5. Type erasure
  6. Summary - Generics

16 Generic collections

  1. List<E>
  2. Map<K,V>
  3. Set<E>
  4. Queue and Deque
  5. Collections class
  6. Summary - Generic collections

17 Iterator

  1. Iterator
  2. remove
  3. ListIterator
  4. Iterable
  5. Spliterator
  6. Summary - Iterator

18 Lambda expressions

  1. Lambda basics
  2. Parameterized lambda
  3. Method reference
  4. forEach with lambda
  5. Comparator with lambda
  6. Summary - Lambda expressions

19 Stream API basics

  1. stream()
  2. filter
  3. map
  4. forEach and count
  5. collect toList
  6. Summary - Stream API basics

20 Intermediate final

  1. Project design
  2. OOP model
  3. Stream layer
  4. File I/O
  5. Putting it together