函数joinToString
函数joinToString想要打印列表的内容,需要传人四个参数:列表、分隔符、前缀和后缀
打印列表的内容:
fun <T> joinToString(collection: Collection<T>,
separator: String,
prefix: String,
postfix: String): String {
val result = StringBuilder(prefix)
for ((index, element) in collection.withIndex()) {
if (index > 0) result.append(separator)
result.append(element)
}
result.append(postfix)
return result.toString()
}
测试:
fun printList() {
val list = listOf(2, 4, 0)
//不标明参数名
println(joinToString(list, " - ", "[", "]"))
//显示的标明参数名称
println(joinToString(list, separator = " - ", prefix = "[", postfix = "]"))
}
定义函数的时候还可以给函数默认的参数
打印列表的内容:(带有默认的参数,可以避免java的函数重载)
fun <T> joinToString2(collection: Collection<T>,
separator: String = ", ",
prefix: String = "",
postfix: String = ""): String {
val result = StringBuilder(prefix)
for ((index, element) in collection.withIndex()) {
if (index > 0) result.append(separator)
result.append(element)
}
result.append(postfix)
return result.toString()
}
测试:
fun printList3() {
val list = listOf(2, 4, 0)
println(joinToString2(list, " - "))
println(joinToString2(list, " , ", "["))
}
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