java category archive

Moving to NetBeans (from Eclipse)

NetBeans Projects Pane

I’m trying out NetBeans 5.5.1 as a Java IDE and I’m very impressed so far. Thought I’d cough up some related thoughts on programming environments and free software, mixed with some personal history:

MS Visual Basic

I began my corporate programming career using Visual Basic 4, and moved on up to VB6, which I continued to use at home until last year. I really liked VB for GUI programming and quickly putting together various utility programs. I’ve probably made over a hundred more or less complicated VB programs for my personal use, in addition to the huge program I worked on at my job many years ago.

Java

While still using VB on the job, I started learning Java and have done a fair amount of …

PermutationIterator.java (in honor of GPLv3)

To celebrate this great day, here’s a little bit of free software, released under the terms of the GNU General Public License, version 3: a Java class I wrote to find all permutations for a given string. I may later post some more in the way of documentation, but for now, por ejemplo:

PermutationIterator p = new PermutationIterator(”123″);
while ( p.hasNext() ) {
System.out.println( p.next() );
}

Produces:

123
132
213
231
312
321

Since we can compute the factorial to know how many total permutations there are for a given string length, it’s a little bit faster to avoid the call to hasNext():

for (int i=0; i < p.totalPermutations(); i++) {
System.out.println( p.next() );
}

You can also supply an integer for “N” and get permutations for an alphabetic string:

p = new PermutationIterator(20);
//…yada yada

To get:

abcdefghijklmnopqrst
abcdefghijklmnopqrts
abcdefghijklmnopqsrt
abcdefghijklmnopqstr
abcdefghijklmnopqtrs
abcdefghijklmnopqtsr
…
2,432,902,008,176,639,993 more permutations…
…
rstqponmlkjihgfedcba

And now for the code, below the fold. Happy GPLv3 …