Collections

Mutable List

Create a mutable list and summarize its values.

mutable A mutable list can be changed after it is created, and it is read like other lists.

Mutable List

added
MutableListExample.kt
Replay: real traced execution (multi-file project)
fun main() {
    val added = 5
    val scores = mutableListOf(3, 4, added)
    val total = scores[0] + scores[1] + scores[2]
    val count = scores.size

    println("total=$total")
    println("count=$count")
}

fun main() {
    val added = 2
    val scores = mutableListOf(3, 4, added)
    val total = scores[0] + scores[1] + scores[2]
    val count = scores.size

    println("total=$total")
    println("count=$count")
}

fun main() {
    val added = 8
    val scores = mutableListOf(3, 4, added)
    val total = scores[0] + scores[1] + scores[2]
    val count = scores.size

    println("total=$total")
    println("count=$count")
}

  1. added ← 5, scores ← [3, 4, 5], total ← 12, count ← 3

    1fun main() {2    val added→ 5 = 5 //@added=2, 83    val scores→ [3, 4, 5] = mutableListOf(3, 4, added5)4    val total→ 12 = scores[0]3 + scores[1]4 + scores[2]55    val count→ 3 = scores.size367    println("total=$total12")8    println("count=$count3")9}
    outputtotal=12
count=3

  1. added ← 2, scores ← [3, 4, 2], total ← 9, count ← 3

    1fun main() {2    val added→ 2 = 23    val scores→ [3, 4, 2] = mutableListOf(3, 4, added2)4    val total→ 9 = scores[0]3 + scores[1]4 + scores[2]25    val count→ 3 = scores.size367    println("total=$total9")8    println("count=$count3")9}
    outputtotal=9
count=3

  1. added ← 8, scores ← [3, 4, 8], total ← 15, count ← 3

    1fun main() {2    val added→ 8 = 83    val scores→ [3, 4, 8] = mutableListOf(3, 4, added8)4    val total→ 15 = scores[0]3 + scores[1]4 + scores[2]85    val count→ 3 = scores.size367    println("total=$total15")8    println("count=$count3")9}
    outputtotal=15
count=3

Sum the Scores

  1. added is 5.
  2. The mutable list starts as 3, 4, and 5.
  3. The code reads each index and adds the values.
  4. The total is 12 and the count is 3. | Index | Score | | --- | --- | | 0 | 3 | | 1 | 4 | | 2 | 5 |

Exercise: MutableListExample.kt

Create a mutable score list, add the indexed values, and print the total and count