kotlin常用语法

package com.kotlin

fun main(arg:Array<String>){
println("hello world");
println("""hello K
ot
lin
""")
println(sum(1,2));

println(hello("Kotlin"))

val arr = arrayOf("A","B","C");
arg0(arr);
forArgs(arr)

println( leng("abc") )
println( leng(123));

println( length("abc") )
println( length(123));

cases("abc")
cases(2)
cases(1)

sumInRanges(1,3)

print("\nis in ranges ? ")
var s=0;
if (s in 1..99999)
println("+");
else if(s in -99999..-1)
println("-")
else
println("0");

println("\narr="+arr.toList())
if("A" in arr)
println("A in arr")
else
println("A not in arr")

var s1="abcde"
var s2="bc"
print("\n"+s2+" in "+s1+" ? ")
if(s2 in s1)
println(true)
else
println(false)
}
fun arg0(args:Array<String>){
println("First argument: ${args[0]}")
}

fun forArgs(args:Array<String>){

for(a in args){
println(a)
}

print("-----\n")

for(i in args.indices)
println(args[i])
}

fun hello(who:String):String="hello,"+who;

fun sum(a: Int, b: Int): Int {
return a + b
}

fun length(s:Any):Int?{
if(s is String)
return s.length
return null;
}

fun leng(s:Any):Int?=if(s is String) s.length else null;

fun cases(obj: Any) {
print(obj)
print(" --> ")
when (obj) {
"Hello" -> print("Hello")
is Int -> print("Int")
1 -> print("One")
!is String -> print("Not a string")
else -> print("Unknown")
}
println()
}

fun sumInRanges( begin:Int, end:Int){
var s=0;
for(a in begin..end){
s=s+a
}
println(""+begin+"+...+"+end+" = "+s);

}



打印如下：
hello world
hello K
ot
lin

3
hello,Kotlin
First argument: A
A
B
C
-----
A
B
C
3
null
3
null
abc --> Unknown
2 --> Int
1 --> Int
1+...+3 = 6

is in ranges ? 0

arr=[A, B, C]
A in arr

bc in abcde ? true