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

2^3 = 8

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() = 6 . 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

Some built-in functions in Java live inside utility classes that need to be imported before you can use them. An import statement at the top of your file tells Java where to find these classes. For array helper functions, you need to add import java.util.Arrays; at the top of your file. Without this line, Java won't recognize the Arrays class and your code won't compile. (Note: The Math and String functions we covered earlier don't require an import because they are part of Java's core java.lang package, which is automatically available.) 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, Java import java.util.Arrays; int[] a = {5, 2, 4, 3, 1}; Arrays.sort(a); System.out.println(Arrays.toString(a)); // Output: [1, 2, 3, 4, 5]

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Using Built-in Functions

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

Java

import java.util.Arrays;

public class Main {
    public static void main(String[] args) {
        // Math functions in action
        System.out.println(Math.max(5, 10));  // prints 10
        System.out.println(Math.pow(3, 2));  // prints 9.0
        System.out.println(Math.sqrt(16));   // prints 4.0
        System.out.println(Math.random());   // prints a random number

        // String functions at work
        String str1 = "Hello", str2 = " World!";
        System.out.println(str1.length());         // prints 5
        System.out.println(str1.charAt(1));        // prints 'e'
        System.out.println(str2.substring(1, 4));  // prints 'Wor'
        System.out.println(str1.concat(str2));     // prints 'Hello World!'
        System.out.println(str1.equals(str2));     // prints false

        // Array functions used
        int[] arr = {7, 2, 10, 5, 3};
        Arrays.sort(arr);
        System.out.println(Arrays.toString(arr));  // prints '[2, 3, 5, 7, 10]'
    }
}

import java.util.Arrays;

public class Main {
    public static void main(String[] args) {
        // Math functions in action
        System.out.println(Math.max(5, 10));  // prints 10
        System.out.println(Math.pow(3, 2));  // prints 9.0
        System.out.println(Math.sqrt(16));   // prints 4.0
        System.out.println(Math.random());   // prints a random number

        // String functions at work
        String str1 = "Hello", str2 = " World!";
        System.out.println(str1.length());         // prints 5
        System.out.println(str1.charAt(1));        // prints 'e'
        System.out.println(str2.substring(1, 4));  // prints 'Wor'
        System.out.println(str1.concat(str2));     // prints 'Hello World!'
        System.out.println(str1.equals(str2));     // prints false

        // Array functions used
        int[] arr = {7, 2, 10, 5, 3};
        Arrays.sort(arr);
        System.out.println(Arrays.toString(arr));  // prints '[2, 3, 5, 7, 10]'
    }
}

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