Sybex CSG 11 - report an error

[Rui Sun]

Hi there,

I have noticed an error in the CSG 11 book. On page 317, the last example
line 2 doesn't compile not line 4

....
private final String type;    //this line DOES NOT COMPILE
....
public MouseHouse() { // DOES NOT COMPILE  -----actually this line compiles
    this.volume = 2;   // DOES NOT COMPILE
}

[Campbell Ritchie]

Welcome to the Ranch

Please supply more details about the book.
It is a convention in cert exam books that they assume fields and imports have been declared before the code blocks. In which case that code might compile after all.

[Mike Simmons]

No, that's not the issue.  The only way that code could compile is if we assume an additional static initializer block.  Otherwise the final field "type" is not initialized.  That's the problem at line 2.

Also, the field "volume" has never been declared - that one could be solved by assuming an unseen field declaration for "volume".  But frankly, that seems a stretch too.  Exam code may omit imports, sure... but field declarations?  That seems a bridge too far, I think.

To be fair, it's possible that different compilers report the location of the error differently.  Because the problem is really a combination of line 2, declaring an unassigned final variable, and line 5 or 6, reaching the end of a constructor without anyone having set the value for that final variable.  Plus the fact that line 5 mentions a different variable, undeclared.

[Campbell Ritchie]

Mike Simmons wrote:No, that's not the issue. . . .

Yes, I was mistaken there. I haven't checked any errata to see whether this is a newly found error

an additional static initializer block. . . .

Instance initialiser, surely?

[Mike Simmons]

Right, slip of the keyboard there.

[Jeanne Boyarsky]

This is the actual example in the book. Which does contain the instance initializer mentioned.

public class MouseHouse {
  private final int volume;
  private final String type;
  {
    this.volume = 10;
  }
  public MouseHouse(String type) {
    this.type = type;
  }
  public MouseHouse() { // DOES NOT COMPILE
    this.volume = 2; // DOES NOT COMPILE
  }
}

And the compiler errors I get are

MouseHouse.java:11: error: variable volume might already have been assigned
this.volume = 2; // DOES NOT COMPILE
    ^
/MouseHouse.java:12: error: variable type might not have been initialized
}

Technically the compiler errors are on this.volume = 2; and the line after (vs before.) But it definitely isn't on private final String type;