kotlin练习 - 集合练习
Set集合
fun main(args: Array<String>) {
//创建不可变集合，返回Set
var set = setOf("java", "kotlin", "go")
println(set)//[java, kotlin, go]
println("setOf 返回类型 ${set.javaClass}")
//创建可变集合，返回值MutableSet
var mutablemap = mutableListOf("java", "kotlin", "go")
mutablemap[0] = "JavaScript"
println(mutablemap)//[JavaScript, kotlin, go]
println("mutableListOf 返回类型 ${mutablemap.javaClass}")
//创建LinkedHashSet集合
var linkedHashSet = linkedSetOf("java", "kotlin", "go")
println(linkedHashSet)
println("linkedHashSet 返回类型 ${linkedHashSet.javaClass}")
//创建HashSet集合
var hashSet = hashSetOf("java", "kotlin", "go")
println(hashSet)//不保证元素的顺序--[kotlin, go, java]
//创建TreeSet集合
var treeSet = sortedSetOf("java", "kotlin", "go")
println(treeSet)//集合按从小到大排列--[go, java, kotlin]
}
//创建不可变集合，返回Set
var set = setOf("java", "kotlin", "go")
//判断是否所有的元素长度都大于5 ------所有元素都满足条件
println(set.all { it.length > 5 })// false
//判断是否任意一元素的长度大于5 ------任意元素都满足条件
println(set.any { it.length > 5 })//true
//以Lambda 表达式的值为key , 集合元素为value ,组成的Map集合
var map = set.associateBy({ "我正在学习${it}" })
println(map)//{我正在学习java=java, 我正在学习kotlin=kotlin, 我正在学习go=go}
//使用in、!in运算符
println("java" in set)// true
println("java" !in set)// false
//删除Set集合前面两个元素
var dropedList = set.drop(2)
println(dropedList)// [go]
//对Set集合进行过滤: 需要得到所有包含 va 的集合,
var filteredList1 = set.filter({ "va" in it })//如果没有返回空元素的集合
println(filteredList1)//[java]
//查找Set集合中包含 va 的元素，如果找到就返回该元素，否则返回 null
var filteredList2 = set.find({ "o" in it })
println(filteredList2)//kotlin
var filteredList3 = set.find({ "va1" in it })
println(filteredList3)//null
//将Set集合中所有字符串拼接在一起
var foldedList1 = set.fold("", { acc, s -> acc + s })
println(foldedList1)//javakotlingo
var foldedList2 = set.fold("456", { acc, s -> acc +" 123 ${s}" })
println(foldedList2)//456 123 java 123 kotlin 123 go
//查找某个元素的出现位置------没有就会返回-1
println(set.indexOf("kotlin"))// 1
println(set.indexOf("kotlin1"))// -1
//循环遍历
var books = setOf("疯狂java讲义", "疯狂kotlin讲义", "疯狂IOS讲义", "疯狂android讲义")
for (book in books){
println(book)
}
books.forEach({
println(it)
})
for (i in books.indices){
println(books.elementAt(i))
}
var books = mutableSetOf("疯狂java讲义")
//新增
books.addAll(setOf("疯狂kotlin讲义", "疯狂IOS讲义"))
books.add("疯狂android讲义")
println(books.toString())//[疯狂java讲义, 疯狂kotlin讲义, 疯狂IOS讲义, 疯狂android讲义]
//删除
books.remove("疯狂kotlin讲义")
println(books.toString())//[疯狂java讲义,疯狂IOS讲义, 疯狂android讲义]
books.removeAll(setOf("疯狂java讲义"))
println(books.toString())//[疯狂IOS讲义, 疯狂android讲义]
//清空所有
books.clear()
println(books.toString())//[]
//只保留公共的元素
books = mutableSetOf("疯狂java讲义", "疯狂kotlin讲义", "疯狂IOS讲义", "疯狂android讲义")
books.retainAll(setOf("疯狂kotlin讲义", "疯狂PHP讲义", "疯狂android讲义"))
println(books.toString())//[疯狂kotlin讲义, 疯狂android讲义]
List集合
var list1 = listOf(1, 2, 3, 4, 5, null, 7, 8, 9)
println(list1.toString())//[1, 2, 3, 4, 5, null, 7, 8, 9]
var list2 = listOfNotNull(1, 2, 3, 4, 5, null, 7, 8, 9)
println(list2.toString())//[1, 2, 3, 4, 5, 7, 8, 9]
var list3 = mutableListOf(1, 2, 3, 4, 5, null, 7, 8, 9)
println(list3.toString())//[1, 2, 3, 4, 5, null, 7, 8, 9]
list3.add(10)
list3.set(5, 6)
println(list3.toString())//[1, 2, 3, 4, 5, 6, 7, 8, 9,10]
var list4 = arrayListOf(1, 2, 3, 4, 5, null, 7, 8, 9)
println(list4.toString())//[1, 2, 3, 4, 5, null, 7, 8, 9]
list4.set(5, 6)
list4.add(10)
println(list4.toString())//[1, 2, 3, 4, 5, 6, 7, 8, 9,10]
//遍历List
var list1 = listOf("Java", null, "Kotlin", "Go")
list1.forEach {
println(it)
}
for (str in list1) {
println(str)
}
for (i in list1.indices) {
println(list1[i])
println("get = ${list1.get(i)}")
println("elementAt = ${list1.elementAt(i)}")
}
var index = list1.indexOf("Go")
println("Go 在数组中的位置：${index}")//3
var list2 = mutableListOf(1, 2, 3, 1, 8, 3, 4, 6, 1, 4, 2, 3)
//最后一次出现的的位置
var last1 = list2.lastIndexOf(2)//10
//最后一次出现的的位置
var last2 = list2.indexOfLast { it == 2 }//10
//第一次出现的位置
var first = list2.indexOfFirst { it == 2 }//1
println("2在数组中第一次出现在${first},最后一次出现在${last1},${last2}")
//返回集合
var list3 = listOf("Java", null, "Kotlin", "PHP", null, "Go")
var sublist = list3.subList(2, 5)//从第2个到第5个之间的元素
println(sublist.toString())//[Kotlin, PHP, null]
// var list4 = mutableListOf("Java", "JavaScript", null, "HTML", "Kotlin", null, "Python", "PHP", "Go")
var list4 = mutableListOf("Java", null, "HTML", "Go")
println(list4)//[Java, null, HTML, Go]
//新增
list4.add("Python")
list4.add(2, "C++")
list4.addAll(listOf("Kotlin", null))
println(list4)//[Java, null, C++, HTML, Go, Python, Kotlin, null]
//删除
list4.removeAt(1)
println(list4)//[Java, C++, HTML, Go, Python, Kotlin, null]
//list4[6] ="CSS";
list4.set(6, "CSS")
println(list4)//[Java, C++, HTML, Go, Python, Kotlin, CSS]
list4.remove("Go")
println(list4)//[Java, C++, HTML, Python, Kotlin, CSS]
list4.add(3, "Go")
list4.add(5, "Go")
println(list4)//[Java, C++, HTML, Go, Python, Go, Kotlin, CSS]
//替换元素
list4.replaceAll {
if (it.equals("Go")) {
"go"
} else {
it
}
}
println(list4)//[Java, C++, HTML, go, Python, go, Kotlin, CSS]
//删除
list4.removeAll(listOf("go"))
println(list4)//[Java, C++, HTML, Python, Kotlin, CSS]
//清空
list4.clear()
println(list4)//[]
Map集合
//不可变map集合
var map1 = mapOf("Java" to 1, "JavaScript" to 2, "HTML" to 3, "Kotlin" to 4)
println(map1)//{Java=1, JavaScript=2, HTML=3, Kotlin=4}
//可变集合MutableMap
var map2 = mutableMapOf("Java" to 1, "JavaScript" to 2, "HTML" to 3, "Kotlin" to 4)
println(map2)//{Java=1, JavaScript=2, HTML=3, Kotlin=4}
map2.put("Python", 5)
println(map2)//{Java=1, JavaScript=2, HTML=3, Kotlin=4, Python=5}
map2.remove("JavaScript")
println(map2)//{Java=1, HTML=3, Kotlin=4, Python=5}
//HashMap集合----不保证key-value的顺序
var map3 = hashMapOf("Java" to 1, "JavaScript" to 2, "HTML" to 3, "Kotlin" to 4)
println(map3)//{Java=1, HTML=3, JavaScript=2, Kotlin=4}
//LinkedHashMap集合---key-value按添加顺序排列
var map4 = linkedMapOf("Java" to 1, "JavaScript" to 2, "HTML" to 3, "Kotlin" to 4)
println(map4)//{Java=1, JavaScript=2, HTML=3, Kotlin=4}
//SortedMap集合------ key-value按key由小到大排列
var map5 = sortedMapOf("Java" to 1, "Python" to 5, "HTML" to 3, "Kotlin" to 4, "JavaScript" to 2, "Go" to 6)
println(map5)//{Go=6, HTML=3, Java=1, JavaScript=2, Kotlin=4, Python=5}
var map1 = mapOf("Java" to 1, "JavaScript" to 2, "HTML" to 3, "Kotlin" to 4)
//当map集合中所有key-value对都满足条件返回true
var all = map1.all {
it.key.length >= 4 && it.value > 0
}
println(all)//true
//当map集合中任意一个key-value对满足条件就会返回true
var any = map1.any {
it.key.length >= 10 && it.value > 1
}
println(any)//true
//判断map集合中是否有对于key的key-value
println("Java" in map1);//true
println("Java" !in map1);//false
println("Go" in map1);//false
println("Go" !in map1);//true
//对map进行过滤，要求key中包含：Java
var filterMap1 = map1.filter { "Java" in it.key }
println(filterMap1)//{Java=1, JavaScript=2}
var filterMap2 = map1.filter { it.key in "Java" }
println(filterMap2)//{Java=1}
//通过map集合，返回一个新的List
var mappedList1 = map1.map { "《疯狂${it.key}》讲义,第${it.value}个" }
var mappedList2 = map1.map { "《疯狂${it.key}》讲义" to "第${it.value}个" }
println(mappedList1)//[《疯狂Java》讲义,第1个, 《疯狂JavaScript》讲义,第2个, 《疯狂HTML》讲义,第3个, 《疯狂Kotlin》讲义,第4个]
println(mappedList2)//[(《疯狂Java》讲义, 第1个), (《疯狂JavaScript》讲义, 第2个), (《疯狂HTML》讲义, 第3个), (《疯狂Kotlin》讲义, 第4个)]
//Map集合中key-value对中 value最大的值
var maxby1 = map1.maxBy { it.value }
println(maxby1)//Kotlin=4
//Map集合中key-value对中 value最小的值
var minby1 = map1.minBy { it.value }
println(minby1)//Java=1
//Map集合中key-value对中 key的长度最大的值
var maxby2 = map1.maxBy { it.key.length }
println(maxby2)//JavaScript=2
//Map集合中key-value对中 key的长度最小的值
var minby2 = map1.minBy { it.key.length }
println(minby2)//Java=1
var map2 = mapOf("Java" to 1, "JavaScript" to 2, "HTML" to 3, "Kotlin" to 4)
var map3 = mapOf("Python" to 1, "Go" to 2, "HTML" to 3, "Kotlin" to 4)
//集合相加---相当于并集
println(map2 + map3)//{Java=1, JavaScript=2, HTML=3, Kotlin=4, Python=1, Go=2}
//集合相减---减去公共的元素
println(map2 - map3)//{Java=1, JavaScript=2, HTML=3, Kotlin=4}
var plus = map2.plus(map3)
println(plus)//{Java=1, JavaScript=2, HTML=3, Kotlin=4, Python=1, Go=2}
var minus = map2.minus(map3)
println(minus)//{Java=1, JavaScript=2, HTML=3, Kotlin=4}
//遍历Map集合
var map4 = mapOf("Java" to 1, "JavaScript" to 2, "HTML" to 3, "Kotlin" to 4, "Go" to 5)
for (en in map4.entries) {
println("${en.key} -> ${en.value}")
}
for (key in map4.keys) {
println("${key} -> ${map4[key]}")
}
for ((key, value) in map4) {
println("${key} -> ${value}")
}
map4.forEach({
println("${it.key} -> ${it.value}")
})
var map5 = mutableMapOf("Java" to 1, "JavaScript" to 2, "HTML" to 3, "Kotlin" to 4, "Go" to 5)
map5["Go"] = 0
println(map5)//{Java=1, JavaScript=2, HTML=3, Kotlin=4, Go=0}
map5.put("HTML", 10)
println(map5)//{Java=1, JavaScript=2, HTML=10, Kotlin=4, Go=0}
map5.remove("Go")
println(map5)//{Java=1, JavaScript=2, HTML=10, Kotlin=4}
map5.remove("Java", 2)
println(map5)//{Java=1, JavaScript=2, HTML=10, Kotlin=4}
map5.remove("Java", 1)
println(map5)//{JavaScript=2, HTML=10, Kotlin=4}
map5.putAll(hashMapOf("PHP" to 6, "C++" to 7,"JavaScript" to 8 ))
println(map5)//{JavaScript=8, HTML=10, Kotlin=4, PHP=6, C++=7}
//清空Map集合
map5.clear()
println(map5)//{}
