scala - Scala 2.10中如何实现惰性val类变量？

Question

This answer到What's the (hidden) cost of Scala's lazy val?展示了它们如何在Scala 2.7中实现。但是正如评论所说，此后一定已经发生了变化，所以我很好奇，当前<2> 10类lazy val变量的实现是什么？

Answer 1

使用scala 2.10.2进行了编译：

class Foo {

  lazy val bar = math.pow(5, 3)

}

然后使用JD-GUI反编译结果：

import scala.math.package.;
import scala.reflect.ScalaSignature;

@ScalaSignature(bytes="\006\001e1A!\001\002\001\013\t\031ai\\8\013\003\r\tq\001P3naRLhh\001\001\024\005\0011\001CA\004\013\033\005A!\"A\005\002\013M\034\027\r\\1\n\005-A!AB!osJ+g\rC\003\016\001\021\005a\"\001\004=S:LGO\020\013\002\037A\021\001\003A\007\002\005!A!\003\001EC\002\023\0051#A\002cCJ,\022\001\006\t\003\017UI!A\006\005\003\r\021{WO\0317f\021!A\002\001#A!B\023!\022\001\0022be\002\002")
public class Foo {

    private double bar;
    private volatile boolean bitmap$0;

    private double bar$lzycompute() {
        synchronized (this) { 
            if (!this.bitmap$0) { 
                this.bar = package..MODULE$.pow(5.0D, 3.0D); 
                this.bitmap$0 = true; 
            } 
            return this.bar; 
        }  
    } 

    public double bar() { 
        return this.bitmap$0 ? this.bar : bar$lzycompute(); 
    }

}

编辑-这是三个字段的外观：

class Foo {

  lazy val a = math.pow(5, 1)
  lazy val b = math.pow(5, 2)
  lazy val c = math.pow(5, 3)

}

反编译：

import scala.math.package.;
import scala.reflect.ScalaSignature;

@ScalaSignature(bytes="\006\001\0052A!\001\002\001\013\t\031ai\\8\013\003\r\tq\001P3naRLhh\001\001\024\005\0011\001CA\004\013\033\005A!\"A\005\002\013M\034\027\r\\1\n\005-A!AB!osJ+g\rC\003\016\001\021\005a\"\001\004=S:LGO\020\013\002\037A\021\001\003A\007\002\005!A!\003\001EC\002\023\0051#A\001b+\005!\002CA\004\026\023\t1\002B\001\004E_V\024G.\032\005\t1\001A\t\021)Q\005)\005\021\021\r\t\005\t5\001A)\031!C\001'\005\t!\r\003\005\035\001!\005\t\025)\003\025\003\t\021\007\005\003\005\037\001!\025\r\021\"\001\024\003\005\031\007\002\003\021\001\021\003\005\013\025\002\013\002\005\r\004\003")
public class Foo {

    private double a;
    private double b;
    private double c;

    private volatile byte bitmap$0;

    private double a$lzycompute() {
        synchronized (this) {
            if ((byte)(this.bitmap$0 & 0x1) == 0) {
                this.a = package..MODULE$.pow(5.0D, 1.0D); 
                this.bitmap$0 = ((byte)(this.bitmap$0 | 0x1)); 
            } 
            return this.a;
        }  
    } 

    private double b$lzycompute() { 
        synchronized (this) {
            if ((byte)(this.bitmap$0 & 0x2) == 0) {
                this.b = package..MODULE$.pow(5.0D, 2.0D); 
                this.bitmap$0 = ((byte)(this.bitmap$0 | 0x2)); 
            } 
            return this.b; 
        }  
    } 

    private double c$lzycompute() { 
        synchronized (this) {
            if ((byte)(this.bitmap$0 & 0x4) == 0) {
                this.c = package..MODULE$.pow(5.0D, 3.0D); 
                this.bitmap$0 = ((byte)(this.bitmap$0 | 0x4)); 
            } 
            return this.c;
        }
    }

    public double a() {
        return (byte)(this.bitmap$0 & 0x1) == 0 ? a$lzycompute() : this.a;
    }

    public double b() { 
        return (byte)(this.bitmap$0 & 0x2) == 0 ? b$lzycompute() : this.b; 
    } 

    public double c() { 
        return (byte)(this.bitmap$0 & 0x4) == 0 ? c$lzycompute() : this.c;
    }

}