Jobsheet 6 - Conditional 2

In the previous jobsheet, we learn about basic conditional. Furthermore, we will discuss about condition inside condition (nested-if).

Conditional syntax if-else-if

In picture above, statement 1 will be executed if condition 1 is true. If condition 1 is false, then the program will check condition 2. If condition 2 is true, then statement 2 will be executed, and so on. And if there are no condition that fullfilled, statement x will be executed. Please check the basic structure below.

if (condition-1) {
  statement-1;
} else if (condition-2) {
  statement-2;
} else if (condition-3) {
  statement-3;
}
...
...
else {
  statement-3;
}

Nested if

In statement if(or if-else) there may be a statement if (if-else). This form called nested-if. As general, the structure can be described below:

if (condition-1) {
  if (condition-2) {
    statement-1;
    ...
    ...
    if (condition-n) {
      statement-2;
    } else {
      statement-3;
    }
  } else {
    statement-n;
  }
} else {
  statement-x;
}

You can also check the flowchart below:

Experiment

Experiment 1

Open your text editor
Create file .java with give name TrafficLight.java
Write basic structure function main()
Add import statement Scanner library in top of program
Declare Scanner variable to receive input
Create variable with String datatype, give name light
Ask user to input the color of light.
Create structure to check condition of light
- if light have green color, display "Please go!"
- if light have yellow color, display "Be carefull!"
- if light have red color, display "Stop!"
- Otherwise display "Wrong Input!"

import java.util.Scanner;

public class TrafficLight {
  public static void main(String[] args) {
    String light;
    Scanner sc = new Scanner(System.in);

    System.out.println("Input the color of light: ");
    light = sc.nextLine();

    if ("green".equals(light))
      System.out.println("Please go!");
    else if ("yellow".equals(light))
      System.out.println("Be carefull!");
    else if ("red".equals(light))
      System.out.println("Stop");
    else
      System.out.println("Wrong input!");
  }
}

Question 1

Explain the meaning of "green".euals(light)
What output if the value of light is red? and why?

Experiment 2

Open your text editor
Create file .java and give name NestedIf.java
Write basic structure function main()
Add import Scanner library at top of program
Declare Scanner
Create variable with int datatype, give name value
Ask value from user
Create structure to check value.
- The value must between 0 - 100, Otherwise display "Invalid input!"
- If the value is valid, check the passing grade of student.
- If the value between 90-100, display "Your grade is A"
- If the value between 80-89, display "Your grade is B"
- If the value between 60-79, display "Your grade is C"
- If the value between 50-59, display "Your grade is D"
- If the value below 50, display "Your grade is E"

import java.util.Scanner;

public class NestedIf {

  public static void main(String[] args) {
    Scanner scanner = new Scanner(System.in);
    System.out.print("Input your value: ");
    int value = scanner.nextInt();

    if (value >= 0 && value <= 100) {
      if (value >= 90) {
        System.out.println("Your grade is A");
      } else if (value >= 80) {
        System.out.println("Your grade is B");
      } else if (value >= 60) {
        System.out.println("Your grade is C");
      } else if (value >= 50) {
        System.out.println("Your grade is D");
      } else {
        System.out.println("Your grade is E");
      }
    } else {
      System.out.println("Invalid value");
    }
  }
}

Question 2

What the output if value is -50? Please explain!
What the output if value is 90? Please explain!

Assignment

Create a program to find the biggest and smallest number from 3 inputted numbers!
Create a program using if-else-if syntax based on flowchart below!
Create a program to calculate the price based on total transaction specifically for members of store. The program needs member id (hardcoded in program), price and amount of item. If the member id is match, then:
- If transaction less than 10 items, then no discount.
- If transaction between 11 - 30 items, get 15% discount.
- If transaction more than 30 items, get 30% discount.
Display ouput total price before discount, discount and total price after discount!
Create a program that receives three input numbers. The input is represents angle value of triangle. If an angle equals to total two of angles, then display "Right Triangle" else "Not Right Triangle". The angle must fullfill requirements below:
- Total three of angles equals to 180°
- The input can't be negative
- Every angle must more than 0° and less than 180°
- Display error message if the input is invalid.

6 - Conditional 2