The Cafes » Java

I hate 1% problems. No this isn’t an OWS slogan. I’m thinking of those code issues that really aren’t a problem 99% of the time, but when they bite, they’re really hard to debug and they cause real pain. Several common cases in Java:

1. Using java.util.Date or java.util.Calendar instead of JodaTime.
2. Not specifying a Locale when doing language sensitive operations such as toLowerCase() and toUpperCase().
3. Not escaping strings passed to SQL, XML, HTML or other external formats.

What I hate most is that it’s really, really hard to convince other developers that these are problems they should take seriously. (more…)

Have you ever seen an Ant error message like this?

BUILD FAILED
/Users/elharo/Projects/XOM/build.xml:545: Problem: failed to create task or type scp
Cause: Could not load a dependent class com/jcraft/jsch/Logger
       It is not enough to have Ant's optional JARs
       you need the JAR files that the optional tasks depend upon.
       Ant's optional task dependencies are listed in the manual.
Action: Determine what extra JAR files are needed, and place them in one of:
        -/opt/ant/lib
        -/Users/elharo/.ant/lib
        -a directory added on the command line with the -lib argument

Do not panic, this is a common problem.
The commonest cause is a missing JAR.

This is not a bug; it is a configuration problem

As usual, the ant error message is completely unhelpful, though for once it’s at least technically correct. (Most of the time when ant says, “This is not a bug; it is a configuration problem”, it is in fact a bug and not a configuration problem.) Here’s what’s really happening.
(more…)

Perhaps the continuing confusion over the difference between checked and runtime exceptions in Java is because we haven’t named them properly. Mosts texts and teachers, including myself, have traditionally focused on how and when you handle the exceptions (compile time or runtime) rather than on what causes each. I propose a modification, not in code, but in terminology and teaching. Specifically I think we should should start calling checked exceptions “external exceptions” and runtime exceptions “internal exceptions”.
(more…)

It’s hard to believe that more than a decade after Java was released, there are still so many tasks it can’t do. I’m not just talking about things it can’t do well, but about things that you just can’t do without shelling out to native code. Here is a list of tasks that still need native code:
(more…)

There are some things I’m reluctant to write about because everything that needs to be said about them has long since been said. This post falls into that category. Peter van der Linden explained what I’m about to say in Expert C Programming: Deep C Secrets years before Java was released, and I have nothing to add to what he wrote. Nonetheless very few C or Java programmers got his message so it’s worth saying again, and repeating until the community finally learns.

Always use braces on multiline if statements

(more…)