loops.md

Loops

• Practice writing for-loops, while-loops, and forEach statements
• Practice writing a constructor

Prerequisites

• Hello World
• Calculator

Instructions

1. Create a new project called Loops and a new Kotlin file within your project. Name the file Main. Create your main method.

2. Create a new Kotlin class within your project and name it Loops.

3. Create a method called basicForLoops. Write four separate for loops that will...

   • Part 1: print variable x in 0-10 inclusive
   • Part 2: print variable x in 0-10 not inclusive of 10
   • Part 3: print variable x in 0-10 inclusive skipping every other number
   • Part 4: print variable x in 10-0 inclusive skipping every other number

4. Create a method called forLoops. Write two separate for loops.

   • Part 1: declare a list called colors of three string elements. Using a for loop, print each element in the list.
   • Part 2: create a new for loop that will iterate through the index and value of each element in colors. In the body of your loop, print the index and value in one line.

5. Create a method called whileLoop. In your method declare an integer variable named x set to 0. Set your loop so that it prints the value of x while x is less than 10. Remember to increase x by 1 in the body of the loop.

6. Create a method called forEachStatement. In your method create a list of two string elements and using a forEach statement, print each of the strings.

7. Create a method called delay. Add two print statements and add code for a 2 second delay between the statements.

8. At the top of your Loops class, add an initializing constructor that prints Initialize

9. Go back to the file with your main method. Inside the main method, create an instance of your Loops class and then call each of the methods from that class. Print the outputs to the console.

Results

Try it yourself before looking at these!

Code

Main.kt

        fun main(){
            val loops = Loops()
            loops.basicForLoops()
            loops.forLoops()
            loops.whileLoop()
            loops.forEachStatement()
            loops.delay()
        }

Loops.kt

    class Loops {

        //constructor
        init{
            println("Initialize")
        }

        fun basicForLoops(){
            print("\n Part 1: ")
            for (x in 0..10) print("$x, ") // Prints 0 through 10 (inclusive)
            print("\n Part 2: ")
            for (x in 0 until 10) print("$x, ") // Prints 0 through 9
            print("\n Part 3: ")
            for (x in 0..10 step 2) print("$x, ") // Prints 0, 2, 4, 6, 8, 10
            print("\n Part 4: ")
            for (x in 10 downTo 0 step 2) print("$x, ") // Prints 10, 8, 6, 4, 2, 0
        }

        fun forLoops(){
            val colors = listOf("red", "green", "blue")
            println("Part 1: ")
            for (color in colors){
                println(color)
            }
            println("Part 2: ")
            for ((index, value) in colors.withIndex()) {
                println("$index: $value")
            }
        }

        fun whileLoop(){
            var x = 0
            while (x < 10) {
                println(x)
                x++
            }
        }

        fun forEachStatement(){
            listOf("Green", "Hope").forEach { word ->
                println(word)
            }
        }

        fun delay(){
            //print after delay of two sec
                println("FRC")
                Thread.sleep(2000)
                println("5190")
        }
    }

Console Output

basicForLoops

        Initialize

        Part 1: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 
        Part 2: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 
        Part 3: 0, 2, 4, 6, 8, 10, 
        Part 4: 10, 8, 6, 4, 2, 0, 
        Process finished with exit code 0

forLoops

    Initialize
    Part 1: 
    red
    green
    blue
    Part 2: 
    0: red
    1: green
    2: blue

    Process finished with exit code 0

whileLoop

    Initialize
    0
    1
    2
    3
    4
    5
    6
    7
    8
    9

    Process finished with exit code 0

forEachStatement

    Initialize
    Green
    Hope

    Process finished with exit code 0

delay

    Initialize
    FRC
    5190

    Process finished with exit code 0