scala数组相关操作

1.定长数组

object Test {

  def main(args: Array[String]): Unit = {
    //定长数组
    val a = Array[Int](10)
    val s = Array("a","b")
    println(s(1))

  }
}

2.变长数组：数组缓冲

import scala.collection.mutable.ArrayBuffer

object Test {

  def main(args: Array[String]): Unit = {
    //变长数组 java中的ArrayList scala中的ArrayBuffer
    val a = ArrayBuffer[Int]() //指定类型后操作
    //添加单个元素
    a += 1
    a += 2
    println(a) //ArrayBuffer(1,2) += 表示在末尾添加
    //添加多个元素
    a += (3, 4, 5)
    println(a) //ArrayBuffer(1, 2, 3, 4, 5)

    //与其他数组链接
    a ++= Array(6, 7)
    println(a) //ArrayBuffer(1, 2, 3, 4, 5, 6, 7)

    //移除后面N个元素
    a.trimEnd(3)
    println(a) //ArrayBuffer(1, 2, 3, 4)  从末尾添加和删除操作都是高效的

    //指定位置添加、删除元素都是低效的，所有在那之后的元素都要平移
    val b = ArrayBuffer[Int](1, 8)
    //插入单个元素
    b.insert(1, 2)
    println(b) //ArrayBuffer(1, 2, 8)
    //插入多个元素
    b.insert(2, 3, 4, 5)
    println(b) //ArrayBuffer(1, 2, 3, 4, 5, 8)
    //删除单个元素
    println(b.remove(5)) //8
    println(b)//ArrayBuffer(1, 2, 3, 4, 5)
    //删除多个
    println(b.remove(2,3)) //()删除3个
    println(b)//ArrayBuffer(1, 2)
    //无法确定数组个数时，先使用数组缓冲，在转为数组
    val c = b.toArray  // [I@742f1989

  }
}

3.遍历数组和数组缓冲

object Test {

  def main(args: Array[String]): Unit = {

    val arr = Array(1, 2, 3, 4, 5, 6)
    for (i <- 0 to arr.length - 1) {
      print(arr(i) + " ")
    }
    for (i <- 0 to(arr.length - 1, 2)) { //步长
      print(arr(i) + " ")
    }
    for (i <- 0 until(arr.length, 2)) {
      print(arr(i) + " ")
    }
    for (a <- arr) {         //类似java中的增强for循环
      print(a + "-")
    }
  }
}

4.数组转换

object Test {

  def main(args: Array[String]): Unit = {

    //数组转换
    val arr = Array(1, 2, 3)
    val result = for (ele <- arr) yield ele * 2 //Array(2, 4, 6)
    //yield生成一个类型与原来类型相同的新的集合

    //if守卫
    val result2 = for (ele <- arr if ele % 2 != 0) yield ele * 2 //Array(2, 6)

  }
}

import scala.collection.mutable.ArrayBuffer

object Test {

  def main(args: Array[String]): Unit = {

    //数组转换
    val arr = Array(2, 1, 3)
    println(arr.sum) //必须是数字类型
    println(arr.min)
    println(arr.max)

    //排序
    val a = arr.sorted
    for (ele <- a) {
      print(ele + " ")
    }

    //mkString  toString
    val arrBuffer = ArrayBuffer(2, 1, 3)
    println(arr.mkString("and")) //2and1and3
    println(arr) //[I@2c72dc45
    println(arrBuffer.mkString("and")) //2and1and3
    println(arrBuffer) //ArrayBuffer(2, 1, 3)

  }
}