These java files are in scala What is the purpose in runtime?

In scala In the runtime directory, there are some * in the scala source tree Java file

Those files seem simple, G. doubleref Java is as follows:

package scala.runtime;

public class DoubleRef implements java.io.Serializable {
    private static final long serialVersionUID = 8304402127373655534L;

    public double elem;
    public DoubleRef(double elem) { this.elem = elem; }
    public String toString() { return java.lang.Double.toString(elem); }
}

Is there any reason why these classes cannot be defined in scala?

Solution

It's also a guess: no Scala constructs are compiled into public fields – public vars in scala are compiled into private fields and public accessors and mutators I imagine that these * ref classes are widely used, which can be an optimization to avoid frequent method calls and replace them with direct field access