Working with Scanner Class

To locate the Scanner class in API documentation:

1. Type "Scanner" in the search bar
2. The dictionary will display various input methods: nextInt(), nextDouble(), nextFloat(), nextLong(), nextByte(), nextShort(), next(), and others.

// Example of using Scanner methods to retrieve different data types
// Import statement: import java.util.Scanner;
import java.util.Scanner;

class InputReader {
    public static void main(String[] args) {
        // Instantiate Scanner object
        InputReader reader = new InputReader();
        Scanner input = new Scanner(System.in);
        
        // Using Scanner methods to capture user input
        System.out.print("Enter your name: ");
        String userName = input.next(); // String input
        System.out.println(userName);
        
        System.out.print("Enter your age: ");
        int userAge = input.nextInt();
        System.out.println(userAge);
        
        System.out.print("Enter your weight: ");
        double bodyWeight = input.nextDouble();
        System.out.println(bodyWeight);
        
        System.out.print("Do you like me? (true/false): ");
        boolean affection = input.nextBoolean();
        System.out.println(affection);

        // For character input, Scanner lacks direct methods. Use string and extract character
        System.out.print("Enter your gender (M/F): ");
        String genderInput = input.next(); // "M"
        char genderChar = genderInput.charAt(0); // Reference API: String class, find char method, index at 0
    }
}

Conditional Branching Examples

Key considerations:

• Match input type with corresponding method - mismatch causes errors
• else blocks are optional
• Percision in condition defniitions is crucial

import java.util.Scanner;
class GradeEvaluator {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        
        System.out.print("Enter student's exam score (0-100): ");
        int grade = scanner.nextInt();
        
        if (grade == 100) {
            System.out.println("Reward: BMW car");
        } else if (grade > 80 && grade <= 99) {
            System.out.println("Reward: iPhone Xs Max");
        } else if (grade >= 60 && grade <= 80) {
            System.out.println("Reward: iPad tablet");
        } else {
            System.out.println("No reward this time");
        }
    }
}

Sorting Three Numbers

This example demonstrates sorting three integers using conditional statements:

import java.util.Scanner;
class NumberSorter {
    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        
        System.out.print("Enter first number: ");
        int firstNum = input.nextInt();
        System.out.print("Enter second number: ");
        int secondNum = input.nextInt();
        System.out.print("Enter third number: ");
        int thirdNum = input.nextInt();
        
        if (firstNum >= secondNum) {
            if (thirdNum >= firstNum) {
                System.out.println(secondNum + ", " + firstNum + ", " + thirdNum);
            } else if (thirdNum <= secondNum) {
                System.out.println(thirdNum + ", " + secondNum + ", " + firstNum);
            } else {
                System.out.println(secondNum + ", " + thirdNum + ", " + firstNum);
            }
        } else {
            if (thirdNum >= secondNum) {
                System.out.println(firstNum + ", " + secondNum + ", " + thirdNum);
            } else if (thirdNum <= firstNum) {
                System.out.println(thirdNum + ", " + firstNum + ", " + secondNum);
            } else {
                System.out.println(firstNum + ", " + thirdNum + ", " + secondNum);
            }
        }
    }
}

Dog Age Calculator

Converts dog years to human equivalent:

class DogAgeConverter {
    public static void main(String[] args) {
        int dogYears = 6;
        if (dogYears >= 0 && dogYears <= 2) {
            System.out.println("Human equivalent: " + dogYears * 10.5);
        } else if (dogYears > 2) {
            System.out.println("Human equivalent: " + (2 * 10.5 + (dogYears - 2) * 4));
        } else {
            System.out.println("Invalid age: dog not born yet");
        }
    }
}

Generating Random Numbers

Using Math.random() with type casting:

int randomValue = (int)(Math.random() * 90 + 10); // Range [10, 99]
// General formula: [a, b] range: (int)(Math.random() * (b - a + 1) + a)

Switch-Case Structure

Syntax pattern:

switch (expression) {
    case constant1:
        statement1;
        // break;
    case constant2:
        statement2;
        // break;
    default:
        statementN;
        // break;
}

Important rules for switch-case:

• Expression supports: byte, short, char, int, Enum (JDK 5.0+), String (JDK 7.0+)
• Identical cases can be merged
• break statements are optional
• Can incorporate if-else within switch blocks

Loop Structures

For loop components:

• Initialization: i = 0
• Condition: i <= 10
• Body: execution code
• Increment: i++

// Basic for loop syntax: for(initialization; condition; increment) { body }

// Example 1: Repetitive output
for(int counter = 0; counter <= 10; counter++) {
    System.out.println("Practice makes perfect through consistent coding");
}

// Example 2: Sequential number printing
for(int num = 1; num <= 100; num++) {
    System.out.println(num);
}

// Example 3: Combining loops with conditions
int sumOdd = 0;
for (int index = 1; index <= 100; index++) {
    if(index % 2 != 0) {
        System.out.println("Odd numbers 1-100: " + index);
        sumOdd += index;
    }
}
System.out.println("Sum of odd numbers 1-100: " + sumOdd);