How to find select the elements that are in one arraylist that are not in another arraylist in kotli-CodePudding

I am attempting to find the difference of 2 arraylists in kotlin i.e the elements in the first arraylist that are not included in the second arraylist. The code below I believe would work for listOf but I need it to work for arraylists of strings structure instead with the same names i.e first, second and difference should all be arraylists of strings.

fun main() {

    private var first = ArrayList<String>()
    private var  second = ArrayList<String>()
    private var difference = ArrayList<String>()

                first.add(“a”)
                first.add(“b”)
                first.add(“c”)
                first.add(“d”)
                first.add(“e”)
                 second.add(“a”)
                 second.add(“b”)
                 second.add(“c”)
val difference = first.minus(second)

println(difference)    // [d, e]

}

CodePudding user response：

You can use arrayListOf:

fun main() {
    val first = arrayListOf("a", "b", "c", "d", "e")
    println("first type: %s".format(first.javaClass.kotlin.qualifiedName))
    val second = arrayListOf("a", "b", "c")
    println("second type: %s".format(second.javaClass.kotlin.qualifiedName))
    val difference = first.minus(second)
    println(difference)
    println("difference type: %s".format(difference.javaClass.kotlin.qualifiedName))
}

Or instead, add the elements to the ArrayList's one by one if desired:

fun main() {
    val first = ArrayList<String>()
    first.add("a")
    first.add("b")
    first.add("c")
    first.add("d")
    first.add("e")
    println("first type: %s".format(first.javaClass.kotlin.qualifiedName))
    val second = ArrayList<String>()
    second.add("a")
    second.add("b")
    second.add("c")
    println("second type: %s".format(second.javaClass.kotlin.qualifiedName))
    val difference = first.minus(second)
    println(difference)
    println("difference type: %s".format(difference.javaClass.kotlin.qualifiedName))
}

Output:

first type: java.util.ArrayList
second type: java.util.ArrayList
[d, e]
difference type: java.util.ArrayList