The JVM doesn’t support TCO natively, so tail recursive methods will need to rely on the Scala compiler performing the optimization.----------"Scala in Depth" 3.5.2

Jvm本身是不支持尾递归优化得，需要编译器支持，而Java编译器不支持，但是Scala支持。写一个简单的计算1到n的和的递归算法验证一下。

public class TestTailRecursion {    private static long sum(long n, long total) {        if (n <= 0) {            return total;        }        return sum(n - 1, total + n);    }    public static void main(String[] args) {        long sum = sum(100000, 0);        System.out.println(sum);    }}

10w（可能每个机器不一样）的时候栈溢出。

object TestTailRecursion {  def sum(n: Long, total: Long): Long = {    if (n <= 0) total    else sum(n - 1, total + n)  }  def main(args: Array[String]) {    val total = sum(10000000, 0)    println(total)  }}

可以讲Scala编译得到的bytecode用JavaDecompiler反编译，看到如下：

import scala.Predef.;import scala.runtime.BoxesRunTime;public final class TestTailRecursion${  public static final  MODULE$;    private TestTailRecursion$()  {    MODULE$ = this;  }    public long sum(long n, long total)  {    for (;;)    {      if (n <= 0L) {        return           total;      }      total += n;n -= 1L;    }  }    public void main(String[] args)  {    long total = sum(10000000L, 0L);    Predef..MODULE$.println(BoxesRunTime.boxToLong(total));  }    static  {    new ();  }}