Decision in Java

Java Conditional Statements Notes

Page 1

Page 2: IF STATEMENT

The Java if statement is a conditional statement that executes a block of code only if a specified condition is true.

Page 3: IF STATEMENT SYNTAX

Syntax:
- if (condition) { // code to be executed if condition is true }

Page 4: Example - Age.java

Code Example:

public class Age {
    public void printAge() {
        byte age = 18;
        if (age >= 18) {
            System.out.println("You are an adult.");
        }
    }
    public static void main(String[] args) {
        Age age = new Age();
        age.printAge();
    }
}

Page 5: Extended Example - Age.java with Scanner

Code Example:

import java.util.Scanner;
public class Age {
    public void printAge() {
        Scanner sc = new Scanner(System.in);
        System.out.println("How old are you?");
        byte age = sc.nextByte();
        if (age >= 18) {
            System.out.println("You are an adult.");
        }
    }
    public static void main(String[] args) {
        Age age = new Age();
        age.printAge();
    }
}

Page 6: IF STATEMENT FLOWCHART

Flowchart Representation:
- True condition: Executes statement(s).
- False condition: Proceeds to the rest of the code.

Page 8: F-ELSE STATEMENT JAVA

Page 9: IF-ELSE STATEMENT

The else statement in Java executes a block of code if the condition of an if statement is false.

Page 10: IF-ELSE STATEMENT SYNTAX

Syntax:
- if (condition) { // code to be executed if condition is true } else { // code to be executed if condition is false }

Page 11: IF-ELSE STATEMENT FLOWCHART

Flowchart Representation:
- START
- Is Condition True?
  - Yes: Executes Statement 1
  - No: Executes Statement 2
- STOP

Page 12: Extended Example - Age.java with IF-ELSE

Code Example:

import java.util.Scanner;
public class Age {
    public void printAge() {
        Scanner sc = new Scanner(System.in);
        System.out.println("How old are you?");
        byte age = sc.nextByte();
        if (age >= 18) {
            System.out.println("You are an adult.");
        } else {
            System.out.println("You are a minor.");
        }
    }
    public static void main(String[] args) {
        Age age = new Age();
        age.printAge();
    }
}

Page 13: DECISIONS ELSE-IF JAVA LADDER

Page 14: ELSE-IF LADDER STATEMENT

In an "else-if ladder," a series of if-else statements are linked together. Each else-if is associated with a specific condition evaluated sequentially.

Page 15: IF-ELSE STATEMENT SYNTAX

Syntax for Else-If:
- if (condition1) { // Code for condition1 true } else if (condition2) { // Code for condition2 true } else if (condition3) { // Code for condition3 true } else { // Code if none are true }

Page 16: Extended Example - TicketPrice

Code Example:

import java.util.Scanner;
public class TicketPrice {
    public void determineTicket() {
        Scanner scanner = new Scanner(System.in);
        System.out.print("Enter your age: ");
        int age = scanner.nextInt();
        if (age >= 0 && age <= 12) {
            System.out.println("Ticket Price: Php 100");
        } else if (age >= 13 && age <= 17) {
            System.out.println("Ticket Price: Php 150");
        } else if (age >= 18 && age <= 59) {
            System.out.println("Ticket Price: Php 250");
        } else {
            System.out.println("Ticket Price: Php 150");
        }
        scanner.close();
    }
    public static void main(String[] args) {
        TicketPrice tp = new TicketPrice();
        tp.determineTicket();
    }
}

Page 17: ELSE-IF STATEMENT FLOWCHART

Flowchart Representation:
- Test Expression 1: If true, execute Statement 1.
- Test Expression 2: If true, execute Statement 2.
- Test Expression 3: If true, execute Statement 3.
- Body of else: Contains the following if-else statement.

Page 18: Extended Example - GradeCalc

Code Example:

import java.util.Scanner;
public class GradeCalc {
    public void printGrade() {
        Scanner scanner = new Scanner(System.in);
        System.out.print("Enter the student's score: ");
        int score = scanner.nextInt();
        if (score >= 95 && score <= 100) {
            System.out.println("Grade: E");
        } else if (score >= 85 && score < 94) {
            System.out.println("Grade: A");
        } else if (score >= 75 && score < 84) {
            System.out.println("Grade: P");
        } else {
            System.out.println("Grade: NI");
        }
    }
    public static void main(String[] args) {
        GradeCalc gc = new GradeCalc();
        gc.printGrade();
    }
}

Page 19: DECISIONS NESTED JAVA IF-ELSE

Page 20: NESTED IF-ELSE STATEMENT

Nested if-else statements refer to the situation where one if-else statement is nested inside another.

Page 21: NESTED IF-ELSE STATEMENT SYNTAX

Syntax:
- if (condition1) { // Code if condition1 true if (condition2) { // Code if both true } else { // Code if condition1 true, but condition2 false } } else { // Code if condition1 false }

Page 22: Extended Example - DriversLicense

Code Example:

import java.util.Scanner;
public class DriversLicense {
    public void license() {
        Scanner scanner = new Scanner(System.in);
        System.out.print("Enter your age: ");
        int age = scanner.nextInt();
        if (age >= 18) {
            System.out.println("You are an adult.");
            System.out.print("Do you have a driver's license? (yes/no): ");
            String hasLicense = scanner.next();
            if (hasLicense.equalsIgnoreCase("yes")) {
                System.out.println("You can drive legally.");
            } else {
                System.out.println("You cannot drive legally without a license.");
            }
        } else {
            System.out.println("You are a minor.");
        }
        scanner.close();
    }
    public static void main(String[] args) {
        DriversLicense dl = new DriversLicense();
        dl.license();
    }
}

Page 23: NESTED IF-ELSE FLOWCHART

Flowchart Representation:
- True condition: Execute Body of nested If.
- False condition: Proceed to else condition.

Page 24: DECISIONS SWITCH JAVA CASE

Page 25: SWITCH CASE STATEMENT

The switch statement enables a program to select among several alternatives, providing efficiency for multiway branching as compared to nested if statements.

Page 26: SWITCH CASE STATEMENT SYNTAX

Syntax:
- switch (expression) { case value1: // Code for value1 break; case value2: // Code for value2 break; // Additional cases as needed default: // Code if expression doesn't match any case }

Page 27: Extended Example - DayofWeek

Code Example:

import java.util.Scanner;
public class DayofWeek {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        System.out.print("Enter a number (1-7): ");
        int dayNumber = scanner.nextInt();
        String day;
        switch (dayNumber) {
            case 1: day = "Sunday"; break;
            case 2: day = "Monday"; break;
            case 3: day = "Tuesday"; break;
            case 4: day = "Wednesday"; break;
            case 5: day = "Thursday"; break;
            case 6: day = "Friday"; break;
            case 7: day = "Saturday"; break;
            default: day = "Invalid day number";
        }
        System.out.println("The day is: " + day);
        scanner.close();
    }
}

Page 28: SWITCH CASE FLOW CHART

Flowchart Representation:
- Expression Matches: Checks each case one by one.
- Default case: If no matches are found, executes the default code.

Page 29: Extended Example - SwitchExample

Code Example:

public class SwitchExample {
    public void day() {
        String day = "Monday";
        switch (day) {
            case "Sunday": System.out.println("It's the first day of the week!"); break;
            case "Monday": System.out.println("It's the start of the workweek."); break;
            case "Friday": System.out.println("It's almost the weekend!"); break;
            default: System.out.println("It's a regular day.");
        }
    }
    public static void main(String[] args) {
        SwitchExample se = new SwitchExample();
        se.day();
    }
}