Decision in Java 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: Age.java Example with If Statement

• 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: Enhanced Age.java Example with User Input

• 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:

  • true condition --> statement(s)

  • false --> rest of code

Page 9: If-Else Statement

• The else statement 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 execute if condition is true } else { //code to execute if condition is false }

Page 11: If-Else Statement Flowchart

• Flowchart:

  • START

  • Is Condition True? --> YES: Statement1

  • NO: Statement2 --> STOP

Page 12: Enhanced 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 14: Else-If Ladder Statement

• In an else-if ladder, a series of if-else statements are linked together. Each else if has a specific condition.

Page 15: Else-If Statement Syntax

• Syntax:

  • if (condition1) { // Code if condition1 is true } else if (condition2) { // Code if condition2 is true } else if (condition3) { // Code if condition3 is true } else { // Code if none conditions are true }

Page 16: TicketPrice.java Example

• 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 18: GradeCalc.java Example

• 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 20: Nested If-Else Statement

• Nested if-else statements involve one if-else statement inside another.

Page 21: Nested If-Else Syntax

• Syntax:

  • if (condition1) { if (condition2) { // Code if both conditions are true } else { // Code if condition1 is true, but condition2 is false } } else { // Code if condition1 is false }

Page 22: DriversLicense.java Example

• 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 24: Switch Statement

• The switch statement provides a multiway branch, allowing a program to select among several alternatives.

Page 25: Switch Case Statement Syntax

• Syntax:

  • switch (expression) { case value1: // Code if expression equals value1 break; case value2: // Code if expression equals value2 break; // Additional cases as needed default: // Code if no cases match }

Page 27: DayofWeek.java Example

• 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 29: SwitchExample.java Example

• 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();  
      }  
    }