add(element:E) : 添加单个元素 示例:setlist.add(“Hello”) addAll(elements: Collection< E >) : 批量添加多个元素; 示例: setlist.addAll(setOf(“Hello”,“Hi”)) 删除元素操作 remove(element:E): 删除指定元素,删除成功返回 true; removeAll(elements: Collection< E >): 批量删除多个元素; retai...
AI代码解释 fun<T>Collection<T>.joinToString(separator:String=" ",prefix:String="[",postfix:String="]"):String{val sb=StringBuilder(prefix)for((index,element)inthis.withIndex()){if(index>0)sb.append(separator)sb.append(element)}sb.append(postfix)returnsb.toString()} 在这里声明成了Collection...
返回值分析 : 返回给定[index]处的元素,如果[index]不在列表范围内,则返回’ null '。 三、List 创建与元素获取代码示例 代码示例 : 代码语言:javascript 代码运行次数:0 运行 AI代码解释 fun main() { var list = listOf("Tom", "Jerry") println("${list[0]}") println(list.getOrElse(2, {"UnK...
public fun Collection<Int>.toIntArray(): IntArray { val result = IntArray(size) var index = 0 for (element in this) result[index++] = element return result } 1. 2. 3. 4. 5. 6. 7. 例子: fun listToArray(){ val list = listOf<Int>(1,2,3,4,5,6) // 声明一个Int类型的...
Example 1: Get Index of Last Occurrence of Element In this example, we will take a list of elements (say strings). We will then find the last index of element"bc"in the list using List.lastIndexOf() function. Kotlin Program </> ...
1.1、List List< T>以指定的顺序存储元素,并提供使用索引访问元素的方法。从第一个元素索引0 到最后一个元素索引(list.size - 1)为止。List的默认实现是ArrayList。 //不可变List,List 的默认实现是 ArrayListval numList =listOf("one","two","three")println(numList[0])//oneprintln(numList.get(0))/...
getOrNull(3)) } 输出 f null 还可以基于lambda表达式删除指定条件的元素 fun main() { val list = mutableListOf("a", "b", "c") list.removeIf{ it == "c" } print(list) } 输出 [a, b] 遍历集合 kotlin中也提供了多种方式来遍历集合: for .. in forEach forEachIndexed fun main() { ...
返回第一个满足条件的元素,没有则抛出NoSuchElementException val list = listOf(1,2,3,4) assertEquals(2,list.first { it > 1 }) firstOrNull 返回第一个满足条件的元素,没有,则 返回Null val list = listOf(1, 2, 3, 4) assertEquals(null, list.firstOrNull { it > 5 }) find 同firstOrNul...
publicinterfaceList<outE>:Collection<E>{override val size:Int override funisEmpty():Boolean override funcontains(element:@UnsafeVarianceE):Boolean override funiterator():Iterator<E>override funcontainsAll(elements:Collection<@UnsafeVarianceE>):Booleanpublicoperator funget(index:Int):EpublicfunindexOf(el...
Kotlin – Get First Element of Array To get the first element of an Array in Kotlin language, use Array.first() method. Call first() method on this array, and the method returns the first element. Syntax The syntax to call first() method on Array arr is </> Copy arr.first() ...