java

recent posts related to java, jdbc, spring, etc.

Java 'import static' example - importing System.out.println and System.err.println

I was just reminding myself how to write a generics class in Java, and for some reason while I was doing that I wanted to use the Java 'import static' capability so instead of typing this:

System.out.println("foo");

I could just use this:

out.println("foo");

The only thing you have to do to make this happen is to use this import static statement at the top of your class:

By Alvin Alexander on October 17, 2012

A Java static initializer block example

I just ran across a nice example of a Java static initializer block example in an Android book, and thought it might be helpful to share that example here.

First, here's the static initialization code:

By Alvin Alexander on February 27, 2013

How to search multiple jar files for a string or pattern

Here's a shell script that I use that search Java jar files for any type of pattern. You can use it to search for the name of a class, the name of a package, or any other string/pattern that will show up if you manually ran jar tvf on each jar file. The advantage of this script -- if you're a Unix, Linux, or Cygwin user -- is that this script will search through all jar files in the current directory.

By Alvin Alexander on October 17, 2012

How to square a number in Java

Java FAQ: How do I square a number in Java?

You can square a number in Java in at least two different ways:

  1. Multiply the number by itself.
  2. Call the Math.pow function.

Here's how to square a number by multiplying it by itself:

i = 2
int square = i * i

In that case, if you print the value of square, it will be 4.

Here's how you call the Math.pow method to square a number:

By Alvin Alexander on October 17, 2012

Java exec - execute a system command pipeline in Java

In earlier articles I've described how to execute system commands from Java applications. A long time ago I wrote my first article on this topic (How to execute system commands from Java), and more recently I wrote an updated version of that article titled "Executing system commands from Java using the ProcessBuilder and Process classes".

By Alvin Alexander on October 17, 2012

Java StringTokenizer - strings, words, and punctuation marks

I was just reading the book, Hadoop in Action, and came across a nice, simple way to use the Java StringTokenizer class to break a sentence (String) into words, taking into account many standard punctuation marks. Before looking at their solution, first take a look at the code they used to break a String into words using whitespace (a blank):

By Alvin Alexander on October 17, 2012

Mac OS X JAVA_HOME location

Since I can never remember this, JAVA_HOME on a Mac OS X system is located here:

/Library/Java/Home

I believe this is correct for Mac OS X 10.5, 10.6, and 10.7 systems.

(This is most likely the shortest blog post I've ever written. :)

 

By Alvin Alexander on October 20, 2012

A Scala cheat sheet in PDF format

I've been working with Scala quite a bit lately, and in an effort to get it all to stick in my brain, I've created a Scala cheat sheet in PDF format, which you can download below.

This PDF is very different from my earlier Scala cheat sheet in HTML format, as I tried to create something that works much better in a print format. (I first tried to get it all in one page, but short of using a one-point font, that wasn't going to happen.)

By Alvin Alexander on November 1, 2012

A printf format reference page (cheat sheet)

Summary: This page is a printf formatting cheat sheet. I originally created this cheat sheet for my own purposes, and then thought I would share it here.

A cool thing about the printf formatting syntax is that the specifiers you can use are very similar, if not identical, between several different languages, including C, C++, Java, Perl, Ruby, and others, so your knowledge is reusable, which is a good thing.

By Alvin Alexander on April 22, 2013

Java String formatting with the String format method

Java String formatting FAQ: How can I format Java String output?

For a long time I appended Java Strings together (using the "+" operator) to combine them into the output format I wanted, but I always knew that approach was pretty ugly. Fortunately at some point I learned how to use the String format method to format my text, and as you'll see, the resulting Java code is much cleaner this way.

By Alvin Alexander on April 22, 2013
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