柯特林集合写入操作
原文:https://www . geeksforgeeks . org/kot Lin-collection-write-operations/
集合写入操作用于更改可变集合的内容。可变集合定义为具有添加和删除等写操作的集合。
-
添加元素 移除元素和 Updating elements
添加元素–
add() 函数用于将元素添加到现有的可变集合组中。它将对象追加到集合的末尾。 科特林程序演示添加一个元素–
kt //add a single element to a list or //a set, use the add() function fun main(args: Array<String>) { val integers = mutableListOf(11, 12, 13, 14) integers.add(15) println(integers) }输出:
kt [11, 12, 13, 14, 15]addAll() 函数用于将列表的所有元素添加到可变集合中。该参数可以是任何形式的可迭代、序列或数组。 科特林计划演示添加元素–
```kt //add multiple elements to a list //or a set, use the addAll() function fun main(args: Array
) { val numbers = mutableListOf(1, 2, 5, 6) // add set elements to list numbers.addAll(2, setOf(2, 13, 14)) println(numbers) // add array elements to list numbers.addAll(arrayOf(7, 8)) println(numbers) } ```
输出:
```kt [1, 2, 2, 13, 14, 5, 6] [1, 2, 2, 13, 14, 5, 6, 7, 8]
```
plussasign(+=)运算符也用于在集合中添加元素。 科特林计划演示添加元素–
```kt //add element to a list //or a set, use the plus operator fun main(args: Array
) { val list = mutableListOf("one", "two", "seven") list += listOf("four", "five") println(list) list += "three" println(list) } ```
输出:
```kt [one, two, seven, four, five] [one, two, seven, four, five, three]
```
元素移除–
remove() 函数用于从可变集合中删除一个元素。它移除元素的第一个匹配项。如果列表中不存在某个元素，则不移除任何内容。 科特林程序演示元素的移除–
kt //remove element to a list //or a set, use the remove() function fun main(args: Array<String>) { val numbers = mutableListOf(11, 22, 33, 44, 33) // removes first occurrence 33 numbers.remove(33) println(numbers) // removes nothing numbers.remove(53) println(numbers) }输出:
```kt [11, 22, 44, 33] [11, 22, 44, 33]
```
removeAll() 函数用于删除所有与参数匹配的元素。 科特林程序演示元素的移除–
kt //remove element to a list //or a set, use the removeAll() function fun main(args: Array<String>) { val counting = mutableSetOf("one", "two", "three", "four") println(counting) // remove all the elements passed as an argument counting.removeAll(setOf("one", "two", "four")) println(counting) }输出:
```kt [one, two, three, four] [three]
```
反赋值(- =)运算符也用于移除集合中的元素。 科特林程序演示元素的移除–
kt //remove element to a list or a set fun main(args: Array<String>) { val counting = mutableListOf("one", "two", "three", "three", "four") counting -= "three" println(counting) // removes the elements counting -= listOf("four", "five", "two") println(counting) }输出:
```kt [one, two, three, four] [one, three]
```
retainal()功能也用于移除元素。它删除条件不满足的元素。 T4【科特林计划–
kt //remove element to a list or a set, use the retainAll() function fun main(args: Array<String>) { val numbers = mutableListOf(11, 22, 33, 44) println(numbers) // only retain the numbers which satisfy the condition numbers.retainAll { it >= 33 } println(numbers) }输出:
kt [11, 22, 33, 44] [33, 44]清除()功能删除所有采集元素。 T4【科特林计划–
kt //remove element to a list or a set, use the clear() function fun main(args: Array<String>) { val numbers = mutableListOf(12, 23, 34, 45) println(numbers) // it empty the list by removing all numbers.clear() println(numbers) }输出:
```kt [12, 23, 34, 45] []
```
元素的更新–
更新元素操作也由可变集合提供。
运算符[] 用于替换给定位置的元素。 T3】科特林项目–
kt //update element to a list fun main(args: Array<String>) { val numbers = mutableListOf("one", "five", "three") numbers[1] = "two" numbers[2] = "two" println(numbers) }输出:
kt [one, two, two]fill()函数用于将所有集合元素替换为指定值.. T4【科特林计划–
kt //update element to a list fun main(args: Array<String>) { val numbers = mutableListOf(1, 2, 3, 4) // replaces all elements by 3 numbers.fill(3) println(numbers) // replaces all elements by 0 numbers.fill(0) println(numbers) }输出:
```kt [3, 3, 3, 3] [0, 0, 0, 0]
```
