scala定长数组和可变数组

定长数组

  def main(args: Array[String]): Unit = {
    //使用new创建定长8的数组，默认值和类型相关
    val arr1 = new Array[Int](5)
    println(arr1) //打印地址
    println(arr1.toBuffer)  //将数组的值放到buffer

    //不使用new方式来定义变长数组，Array定义，实则用Array的apply()方法
    val arr2 =Array[Int](8)
    println(arr2.toBuffer)  //赋值元素为8

    //定义数组并赋值
    val arr3 = Array(123,"hello",'a',789)
    println(arr3.toBuffer)  //ArrayBuffer(123, hello, a, 789)

    //操作可变数组
    var arr4 = new Array[String](4)
    //赋值
    arr4(0) = "hello"
    arr4(1) = "hadoop"
    arr4(2) = "hive"
    arr4(3) = "spark"
    //打印
    println(arr4.toBuffer)  //ArrayBuffer(hello, hadoop, hive, spark)

    //修改值
    arr4(1) = "scala"
    println(arr4.toBuffer)  //ArrayBuffer(hello, hadoop, hive, spark)
    arr4.update(0,"hbase")

    //获取元素
    println(arr4(1))
    println(arr4.apply(1))

    //遍历
    for(i <- arr4){
      print(i + " ")
    }

    println()

    //如果数组想删除，需要转换成list
    val list = arr4.toList
    println(list)
    val li = list.drop(1)
    println(li) //List(scala, hive, spark)
    //tail是取集合从后往前的除第一个以外的元素
    println(li.tail)  //List(hive, spark)
  }

可变数组

object MutableArray {
  def main(args: Array[String]): Unit = {
  //使用new ArrayBuffer()  定义一个可变的数组
    val arr1 : ArrayBuffer[String] = new ArrayBuffer[String]()
    
    //添加元素
    arr1 += "hadoop"
    //arr1(1) = "spark"
    arr1 += ("hive","hbase")
    arr1 ++= ArrayBuffer("scala","sqoop")
    println(arr1)

    //在指定位置添加元素
    arr1.insert(1,"flume")
    arr1.insert(1,"kafka","kylin")
    arr1.insertAll(1,ArrayBuffer("hello","world"))
    println(arr1)

    //更新元素
    arr1(1) = "insistent"
    arr1.update(2,"java")

    println(arr1)

    //获取指定元素
    println(arr1(1))
    println(arr1.apply(2))
    println(arr1.take(3))

    //遍历
    for(i <- arr1){
      print(i + " ")
    }
    println()

    //删除元素
    arr1 -= "insistent"
    arr1 -= ("java","kafka")
    arr1.remove(1)
    arr1.remove(1,3)
    arr1.trimEnd(1) //从后往前移除n个元素
    arr1.trimStart(1) //从后往前移除n个元素
    println(arr1)

  }