简单的分组算法

Grouping.kt

internal object MapTest {
    @JvmStatic
    fun main(args: Array<String>) {

        /*1、准备数据**/
        val sku1 = Student(1L, "p1", 100L)
        val sku2 = Student(2L, "p2", 101L)
        val sku5 = Student(2L, "p5", 100L)
        val sku3 = Student(3L, "p3", 102L)
        val sku4 = Student(3L, "p3", 102L)
        val sku6 = Student(5L, "p6", 100L)

        val studentLists = Arrays.asList<Student>(sku1, sku2, sku3, sku4, sku5, sku6)

        /*2、分组算法**/
        val map = LinkedHashMap<Long, ArrayList<Student>>()

        for (Student in studentLists) {
            var tempList: ArrayList<Student>? = map[Student.age]

            if (tempList == null) {
                tempList = ArrayList()
                tempList.add(Student)
                map[Student.age] = tempList
            } else {
                // 如果Student.age重复,可以利用HashSet的特性进行去重
                tempList.add(Student)
            }
        }

        /*3、遍历map,验证结果**/
        for (skuId in map.keys) {
            println(map[skuId])
        }

    }
}