字符串插值vs级联

发布时间：2020-12-16 09:17:12 所属栏目：安全来源：网络整理

导读：字符串插入是否比连续化在 scala中构建一个字符串更好？例如： val myVal = "def"val test = s"abs${myVal}ghi" VS val test = "abc" + myVal + "ghi" 我要问的是因为我需要为一个有很多参数的类写入toString方法,因此插入的字符串因此变得很长时间并且令人

字符串插入是否比连续化在 scala中构建一个字符串更好？例如：

val myVal = "def"
val test = s"abs${myVal}ghi"

val test = "abc" + myVal + "ghi"

我要问的是因为我需要为一个有很多参数的类写入toString方法,因此插入的字符串因此变得很长时间并且令人困惑,我想将其分解成多行,但是如果我串连.

解决方法

我做了一个简单的例子：

class Employee(name: String,age: Int) {
  private var s = 0.0
  def salary = s
  def salary_=(s: Double) = this.s = s
  def toStringConcat(): String = {
    "Name: " + name + ",age: " + age + ",salary: " + salary
  }
  def toStringInterpol(): String = {
    s"Name: $name,age: $age,salary: $salary"
  }
}

object Program {
  val empl = new Employee("John",30)
  empl.salary = 10.50
  val times = 10000000;

  def main(args: Array[String]): Unit = {
    // warming-up
    val resultConcat = empl.toStringConcat
    val resultInterpol = empl.toStringInterpol
    println("Concat -> " + resultConcat)
    println("Interpol -> " + resultInterpol)

    val secondsConcat0 = run(empl.toStringConcat)
    val secondsInterpol0 = run(empl.toStringInterpol)
    val secondsConcat1 = run(empl.toStringConcat)
    val secondsInterpol1 = run(empl.toStringInterpol)

    println("Concat-0: " + secondsConcat0 + "s")
    println("Concat-1: " + secondsConcat1 + "s")
    println("Interpol-0: " + secondsInterpol0 + "s")
    println("Interpol-1: " + secondsInterpol1 + "s")
  }

  def run(call: () => String): Double = {
    val time0 = System.nanoTime()
    var result = ""
    for (i <- 0 until times) {
      result = call()
    }
    val time1 = System.nanoTime()

    val elapsedTime = time1 - time0;
    val seconds = elapsedTime / 1000000000.0;
    seconds
  }
}

结果如下：

Concat -> Name: John,age: 30,salary: 10.5
Interpol -> Name: John,salary: 10.5
Concat-0: 2.831298161s
Concat-1: 2.725815448s
Interpol-0: 3.846891864s
Interpol-1: 3.753401004s

内插情况较慢.原因可以在生成的代码中找到：

public String toStringConcat()
  {
    return new StringBuilder().append("Name: ").append(this.name).append(",age: ").append(BoxesRunTime.boxToInteger(this.age)).append(",salary: ").append(BoxesRunTime.boxToDouble(salary())).toString();
  }

  public String toStringInterpol()
  {
    return new StringContext(Predef..MODULE$.wrapRefArray((Object[])new String[] { "Name: ",",age: ",salary: ","" })).s(Predef..MODULE$.genericWrapArray(new Object[] { this.name,BoxesRunTime.boxToInteger(this.age),BoxesRunTime.boxToDouble(salary()) }));
  }

我使用Scala 2.10.3和IntelliJ IDEA 13.

（编辑：李大同）

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