Kotlin for 循环写法整理
Posted android阿杜
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1、Map 的 in 运算符方式:
fun forMap1()
val map = hashMapOf<String, String>("name" to "Hili", "age" to "93")
for ((k, v) in map)
println("$k -> $v")
输出:
name -> Hili
age -> 93
2、List 的 in 运算符方式:
fun forList1()
val list = listOf("apple", "banana", "kiwifruit")
for (item in list)
println(item)
输出:
apple
banana
kiwifruit
3、List 的 in 运算符方式,带上数据类型:
fun forList2()
val list = listOf("apple", "banana", "kiwifruit")
for (item: String in list)
println(item)
输出:
apple
banana
kiwifruit
4、List 的 indices 索引方式:
fun forList3()
val list = listOf("apple", "banana", "kiwifruit")
for (index in list.indices)
val str = "item at $index is $list[index]"
println(str)
输出:
item at 0 is apple
item at 1 is banana
item at 2 is kiwifruit
5、List 的 withIndex() 库函数方式:
fun forList4()
val list = listOf("apple", "banana", "kiwifruit")
// 库函数 withIndex() 获取索引
for ((i, v) in list.withIndex())
val str = "the element at $i is $v"
println(str)
输出:
the element at 0 is apple
the element at 1 is banana
the element at 2 is kiwifruit
6、Array 的 in 运算符方式(同 List):
fun forArray1()
val array = arrayOf("java", "c plus plus", "kotlin", "python")
for (item in array)
println(item)
输出:
java
c plus plus
kotlin
python
7、Array 的 in 运算符方式,带上数据类型(同 List):
fun forArray2()
val array = arrayOf("java", "c plus plus", "kotlin", "python")
for (item: String in array)
println(item)
输出:
java
c plus plus
kotlin
python
8、Array 的 indices 索引方式(同 List):
fun forArray3()
val array = arrayOf("java", "c plus plus", "kotlin", "python")
for (index in array.indices)
val str = "item at $index is $array[index]"
println(str)
输出:
item at 0 is java
item at 1 is c plus plus
item at 2 is kotlin
item at 3 is python
9、Array 的 withIndex() 库函数方式(同 List):
fun forArray4()
val array = arrayOf("java", "c plus plus", "kotlin", "python")
// 库函数 withIndex() 获取索引
for ((i, v) in array.withIndex())
val str = "the element at $i is $v"
println(str)
输出:
the element at 0 is java
the element at 1 is c plus plus
the element at 2 is kotlin
the element at 3 is python
10、.. (rangeTo()) 方式:
fun forRange1()
for (item in 1..5)
print(item)
输出:
1
2
3
4
5
11、.. (rangeTo()) step 方式:
fun forRange2()
for (item in 0..10 step 3)
print(item)
输出:
0
3
6
9
12、.. (rangeTo()) downTo 方式:
fun forRange3()
for (item in 10 downTo 0)
print(item)
输出:
10
9
8
7
6
5
4
3
2
1
0
13、.. (rangeTo()) downTo step方式:
fun forRange4()
for (item in 10 downTo 0 step 3)
print(item)
输出:
10
7
4
1
14、until [闭,开) 区间方式:
fun forRange5()
for (item in 0 until 10)
print(item)
输出:
0
1
2
3
4
5
6
7
8
9
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