循環

列印出List(names)中的每一項

val names = listOf("Root", "Java", "Lua","Flutter", "R&B", "Crips")
for (name in names) { 
    println(name) 
}

for(name in names)
names 代表上方所宣告的List集合
name 是在迴圈中所使用的變數 盡量不要與外部宣告變數重疊

利用 .. 的方式讓x設定區間

for(x in 0..10) 
    Log.d("xxx","$x")

輸出 0-10

設定區間並且排除最後一個數字

for (x in 0 until 10)
    Log.d("xxo","$x") 

輸出 0-9

step讓區間數字0到10 間隔2

for (x in 0 until 10 step 2)
    Log.d("xxoo","$x") 

输出 0, 2, 4, 6, 8

downTo的方式讓製作遞減迴圈

重點 step 後的數字不允許負數

for (x in 10 downTo 0 step 2)
    println(x)

输出 10, 8, 6, 4, 2, 0

快速建置連續整數numbers的List

val numbers = (0..9).toList() 
Log.d("xxooO","$numbers")

輸出 [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

取出names的List每一項的索引和數值

 val names = listOf("Root", "Java", "Lua","Flutter", "R&B", "Crips")
 for ((index, value) in names.withIndex()) {
     println("$index: $value")
 }

輸出 0:Root 1:Java 2:Lua 3:Flutter 4:R&B 5:Crips

while 輸出0-9

var x = 0
while (x < 10) {
    println(x)
    x++ 
}

x++ 等同于 x += 1