How can we combine 2 array lists in java [duplicate] import java.util.* fun main(args: Array) { val firstArray = arrayOf(-1, 2, 3) val secondArray = arrayOf(1,2,-3,4) println(Arrays.toString(firstArray)) println(Arrays.toString(secondArray)) val iArray = firstArray.intersect(secondArray.toList()).toIntArray() println(Arrays.toString(iArray)) } the above program returned [2] how can we achieve like [-1,2,3],[1,2,-3,4] would return [[-1,1],[2,2],[3,-3]]