Verifying Results in Tests

5. March, 2009

So you finally got yourself writing a test against a database. In the test, you have to verify that a row in the table is correct, so you write:

assertEquals (
    "2008-09-16-;;;;1;2008-08-07;2008-08-07;JUNIT;2008-09-16;t0001;001;;Doe;Jane;;Street;2;Doe Jane;;;;;X;2575;John;;;;US;E;;01;;;;125;01425;0;Shop;;;DOE;JANE;JOHN;032;1;;0001010301;;;;",

and it sucks. Yeah, junit will notify you when something in that row is wrong and if you have a cool IDE, you can even compare the fields … but it still sucks. If one of the fields in the middle change, you have to scroll and eyeball-diff, wasting your time. The solution is pretty simple:

assertEquals (
    + "\n"
    + "\n"
    + "\n"
    + "1\n"
    + "2008-08-07\n"
    + "2008-08-07\n"
    + "JUNIT\n"
    + "2008-09-16\n"
    dumpRow(key).replaceAll(";", "\n");

Instead of dumping the data in a single long string, split it into lines so you can compare fields side by side and without scrolling sideways.

Java Tricks: Commenting Out Code

25. February, 2009

How do you comment out code? Using /*...*/? Using your IDE to put // before each line? There is a third method:

    if (0 == 1) {
        ... code ...


  • Nests
  • You need only change a single character to “flip” the comment: Replace the 0 with 1.
  • You won’t get warnings because of suddenly unused imports or local variables.
  • The Java compiler will remove this block of code in the optimization step, so no runtime penality.


  • Can only be used inside of methods.

If you need a fast way to repeatedly comment in/out a piece of code elsewhere, use this syntax:

    //* Fast flip comment starts here
        ... code ...
    /* and ends here */

Inside of a /*...*/ comment, the sequence “/*” has no special meaning. To comment out the block of code, remove the first “/” in “//*”:

    /* Fast flip comment starts here
        ... code ...
    /* and ends here */

Java Tricks: Fastest Way to Collecting Objects in a String

11. July, 2008

The fastest way to collect a list of objects in a String in Java:

StringBuilder buffer = new StringBuilder ();
String delim = "";
for (Object o: list)
    buffer.append (delim);
    delim = ", "; // Avoid if(); assignment is very fast!
    buffer.append (o);
buffer.toString ();