If I have items like this

-> [1,2,3,4,5,6,7,8,9,10]

And if ChunkSize =3, spring batch ItemReader reads item like

[1,2,3]
[4,5,6]
[7,8,9]
[10]

But, I want to

[1,2,3]
[4,5,6]
[7,8,9,10]

Is there any way to do this?

CodePudding user response：

You can make the adjustment by checking the size of the last item in the result, and if it's smaller than the chunkSize, then append it to the second-last item of the result:

fun main() {
    val l = listOf(1,2,3,4,5,6,7,8,9,10,11)
    val chunkSize = 3
    val c = l.chunked(chunkSize)
    println(c)
    val d = if (c.size >= 2 && c.last().size < chunkSize)
            c.slice(0..c.lastIndex - 2)   listOf(c[c.lastIndex - 1]   c.last())
        else
            c
    println(d)
}

Output:

[[1, 2, 3], [4, 5, 6], [7, 8, 9], [10]]
[[1, 2, 3], [4, 5, 6], [7, 8, 9, 10]]

CodePudding user response：

val list = listOf(1, 2, 3, 4, 5, 6, 7, 8, 9, 10)

val chunkSize = 3

val result = list.chunked(chunkSize)
  .run {
    if (isNotEmpty() && last().count() != chunkSize) {
      dropLast(2)   listOf(takeLast(2).flatten())
    } else {
      this
    }
  }

println(result)   // Output: [[1, 2, 3], [4, 5, 6], [7, 8, 9, 10]]