Given a class containing a method switching on an enum, like this:

1:  public class WeirdConstructorLinenumber
2:  {
3:     public void consider(java.math.RoundingMode mode) {
4:         switch ( mode ) {}
5:     }
6:  }

javac generates a default constructor as expected.

But the generated constructor returns from line 4 (which really belongs to the "consider" method).

$ javac WeirdConstructorLinenumber.java 
$ javap -c -l -classpath . WeirdConstructorLinenumber
Compiled from "WeirdConstructorLinenumber.java"
public class WeirdConstructorLinenumber {
  public WeirdConstructorLinenumber();
    Code:
       0: aload_0
       1: invokespecial #1                  // Method java/lang/Object."<init>":()V
       4: return
    LineNumberTable:
      line 1: 0
      line 4: 4

   [...]
}