Decision in Java

Java Conditional Statements

Overview of Conditional Statements

• Conditional statements allow executing different blocks of code based on specified conditions.

IF STATEMENT

Definition

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

Syntax

• The basic syntax of an if statement is:

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

Example of IF Statement

• Age.java 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();
      }
  }

Flowchart Representation

• Flowchart illustrates the flow of control based on the condition being true or false:

  • If condition is true: Execute statements

  • If condition is false: Proceed to other code

IF-ELSE STATEMENT

Definition

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

Syntax

• The basic syntax:

  if (condition) {
      // code if condition is true
  } else {
      // code if condition is false
  }

Example of IF-ELSE Statement

• Age.java Example with else:

  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();
      }
  }

Flowchart Representation

• Flowchart illustrates decision flow based on true or false conditions:

  • Start

  • Test condition

  • Execute appropriate statement based on the result

ELSE-IF STATEMENT

Definition

• The else-if ladder permits multiple conditions to be checked in sequence. If one condition is true, its block executes, skipping others.

Syntax

• The basic syntax for an else-if sequence is:

  if (condition1) {
      // code if condition1 is true
  } else if (condition2) {
      // code if condition2 is true
  } else {
      // code if none of the conditions are true
  }

Example of ELSE-IF Statement

• TicketPrice.java 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();
      }
  }

Flowchart Representation

• Flowchart represents flow of evaluation for each condition which leads to respective code execution.

NESTED IF-ELSE STATEMENT

Definition

• Nested if-else statements occur when one if-else is contained within another, allowing for more complex decision-making.

Syntax

• The basic syntax:

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

Example of NESTED IF-ELSE Statement

• DriversLicense.java 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();
      }
  }

Flowchart Representation

• Flowchart describes the decision-making path that includes nested conditions.