Lesson 3

Unlocking the Power of Java's Built-In Functions

Lesson Overview

Welcome, Cosmic Coder! Today, we are venturing into the realm of Java's built-in functions — pre-packaged tools that will turbocharge your coding experience. Our journey includes acquainting ourselves with built-in functions, their variations uses, tips, and some hands-on coding.

Types of Built-In Functions

Built-in functions are like freebies in Java. They are built-in and ready to use. You just call them, and they respond, making your programming life easier!

Java offers a wide range of built-in functions that mostly fit under three categories — Math, String, and Array. Let's dive in!

Built-in Functions: Mathematical Functions

Java's Math class is your calculator. Key functions include:

  • Math.max(a, b): It resolves the "which number is greater" debate! For example, Math.max(8, 10) = 10.

  • Math.pow(a, b): Raises a to the power b. For example, Math.pow(2, 3) = 8.0, as 23=82^3 = 8.

  • Math.sqrt(a): Calculates the square root of a. For example, Math.sqrt(16) = 4, as 16=4\sqrt{16} = 4.

  • Math.random(): Returns a float random number from 0.0 to 1.0, adding an element of surprise.

Built-in Functions: String Manipulation Functions

Java strings carry built-in methods for manipulation:

  • str.length(): Measures the size of string str. For example, "Hello!".length() = 5.

  • str.charAt(index): Finds the character at the index-th location of string str. For example, "Hello!".charAt(0) = 'H'.

  • str.substring(startIndex, endIndex): Carves out a part of the narrative str from startIndex (inclusive) to endIndex (exclusive). For example, "Hello".substring(1, 3) = "el".

  • str.concat(anotherStr): Merges str and anotherStr into one string. For example, "Hello".concat(" world") = "Hello world".

  • str.equals(anotherStr): Checks if str and anotherStr match completely. For example, "Hello".equals("Hello") = true.

Built-in Functions: Array Functions

Java arrays come with built-in functions:

  • Arrays.toString(arr): Translates arr into a string.
  • Arrays.sort(arr): Organizes arr in ascending order, much like arranging books alphabetically. For example,
1int[] a = {5, 2, 4, 3, 1}; 2Arrays.sort(a); 3System.out.println(Arrays.toString(a)); // Output: [1, 2, 3, 4, 5]
Using Built-in Functions

Let's get hands-on with a sample code:

1import java.util.Arrays; 2 3public class Main { 4 public static void main(String[] args) { 5 // Math functions in action 6 System.out.println(Math.max(5, 10)); // prints 10 7 System.out.println(Math.pow(3, 2)); // prints 9.0 8 System.out.println(Math.sqrt(16)); // prints 4.0 9 System.out.println(Math.random()); // prints a random number 10 11 // String functions at work 12 String str1 = "Hello", str2 = " World!"; 13 System.out.println(str1.length()); // prints 5 14 System.out.println(str1.charAt(1)); // prints 'e' 15 System.out.println(str2.substring(1, 4)); // prints 'Wor' 16 System.out.println(str1.concat(str2)); // prints 'Hello World!' 17 System.out.println(str1.equals(str2)); // prints false 18 19 // Array functions used 20 int[] arr = {7, 2, 10, 5, 3}; 21 Arrays.sort(arr); 22 System.out.println(Arrays.toString(arr)); // prints '[2, 3, 5, 7, 10]' 23 } 24}

Copy this into your environment or the CodeSignal IDE and run it to get a hands-on understanding of Java's built-in functions.

Lesson Summary and Practice

Marvelous! You've navigated through Java's universe of built-in functions, discovering their types, uses, and pitfalls. Java's built-in functions are at your service, ready to accelerate your coding speed.

Next, it's practice time! The exercises are designed to let you apply and sharpen your newly acquired skills. Remember, every problem solved brings you closer to mastering Java! Let's keep coding and exploring!

Enjoy this lesson? Now it's time to practice with Cosmo!

Practice is how you turn knowledge into actual skills.