Cutting a Large Sheet of Paper in Half

22. April, 2009 at 11:24 | In Fun | Leave a Comment
Tags:

Here is a simple trick how to cut a large piece of paper or cardboard into two perfectly symmetrical halves:

Cutting large piece of cardboard in half

Cutting large piece of cardboard in half

  1. Fold the paper. Make sure that the open side matches perfectly. Put some weights on them to keep them in place.
  2. Now sharpen the fold. Use a book or the handles of your scissors. It doesn’t have to be razor sharp, though.
  3. Cut the fold away with a knife or scissors.

It’s simple to make a straight cut when you only have to keep 1-2mm distance to the edge of the fold. Also, even if you’re completely inept, the two pieces will have the exact same width at the point where you started. If you need to glue them together, they will match perfectly.

Verifying Results in Tests

5. March, 2009 at 11:46 | In Software | Leave a Comment
Tags: , , ,

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 (
    "2008-09-16-13.50.18.000000;;;;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;;;;",
    dumpRow(key));

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 (
    "2008-09-16-13.50.18.000000\n"
    + "\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 at 10:05 | In Software | Leave a Comment
Tags: , ,

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

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

Pros:

  • 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.

Cons:

  • 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 at 19:08 | In Software | Leave a Comment
Tags: , ,

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 ();

Blog at WordPress.com. | Theme: Pool by Borja Fernandez.
Entries and comments feeds.