1.mkString()方法的使用:
- mkString(seq:String)方法是将原字符串使用特定的字符串seq分割。
- mkString(statrt:String,seq:String,end:String)方法是将原字符串使用特定的字符串seq分割的同时,在原字符串之前添加字符串start,在其后添加字符串end。
object Test { def main(args: Array[String]): Unit = { var name : String = "Hello LittleLawson" var age :Int = 2 println(name.mkString) println(name.mkString(" "))//separate string with space var str0 = "scala" println(str0.mkString(","))//separate string with comma println(str0.mkString("begin",",","end")) /* 1.mkString is used in the inner List,That is say ,Elements in the list is applied. */ val a = List(1,2,3,4) val b = new StringBuilder() println(a.mkString("List(" , ", " , ")")) } }
执行结果如下:
Hello LittleLawson
H e l l o L i t t l e L a w s o n
s,c,a,l,a
begins,c,a,l,aend
List(1, 2, 3, 4)Process finished with exit code 0
2.scala通过mkString方法把一个集合转化为一个字符串
Problem
如果你想要把集合元素转化为字符串,可能还会添加分隔符,前缀,后缀。
Solution
使用mkString方法来打印一个集合内容,下面给一个简单的例子:
scala> val a = Array("apple", "banana", "cherry") a: Array[String] = Array(apple, banana, cherry) scala> a.mkString res3: String = applebananacherry
使用mkString方法你会看到结果并不漂亮,我们来加一个分隔符:
scala> a.mkString(",") res4: String = apple,banana,cherry scala> a.mkString(" ") res5: String = apple banana cherry
这样看起来就好看多了,同样你可以添加一个前缀和一个后缀:
scala> a.mkString("[", ", ", "]") res6: String = [apple, banana, cherry]
如果你想把一个潜逃集合转化为一个字符串,比如嵌套数组,首先你要展开这个嵌套数组,然后调用mkString方法:
scala> val a = Array(Array("a", "b"), Array("c", "d")) a: Array[Array[String]] = Array(Array(a, b), Array(c, d)) scala> a.flatten.mkString(",") res7: String = a,b,c,d
Discussion
你可以调用集合的toString方法,但是它返回带有集合元素信息的集合名称:
scala> val v = Vector("apple", "banana", "cherry") v: scala.collection.immutable.Vector[String] = Vector(apple, banana, cherry) scala> v.toString res8: String = Vector(apple, banana, cherry)
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