Masood Mortazavi's Blog

September 2006 Archives

Derby 10.2 Release Candidate

Sun's Java DB team has been working hard contributing to the Apache Derby project, and now, the release candidate for Derby 10.2 is available for early use and testing.

Many of you already know that Derby is a database implemented in Java by the Apache community.

Historically, it goes back to Cloudscape, a Java database developed by a startup of the same name in the late 1990s. Cloudscape later came to IBM following a series of acquisitions. IBM contributed it to Apache in August of 2004. Sun joined the development effort in spring of 2005. Derby came out of Apache incubation and became a full-fledged Apache project in December of 2005.

Sun distributes Derby as Java DB. (JDK 6 is expected to distribute a version of Java DB which contains JDBC 4.)

JRuby

Arrays, Variables, [ and {

Variable initialization, assignments and use in array construction can be tricky to varying degrees in different programming languages.

When a variable is used during initialization of an array, some may assume that assignment to that variable will be carried to the array, too.

In this short note I want to give a couple of examples to note the difference between "{ }" and "[ ]" which are used when it comes to array assignments and initialization in Java. In fact, "{" and "[" distinctively mark assignment during innitialization or later.

I'm just going to give the code fragments and leave it there. I give two examples. One from Java and one from Ruby. My purpose here is not to be correct style-wise but simply to make a point that you probably already know but might forget once in a while. Try to run them on your own, fix any bugs and see what the difference is.

Here is the Java fragment:

public class TestVariableMeaningInArrays{
  public static void main(String args[ ])
  {
    String[ ] x={"Iran", "US"}, y={"Tehran", "Washington DC"};
    String[ ][ ] z={x,y};
    print2By2(z);
    y[0]="Isfahan";
    y[1]="Chicago";
    print2By2(z);
    y=new String[ ]{"Shiraz", "Santa Barbara"};
    print2By2(z);
  }
  private static void print2By2(String[ ][ ] z){
    System.out.println(z[0][0]);
    System.out.println(z[0][1]);
    System.out.println(z[1][0]);
    System.out.println(z[1][1]);
  }
}

  x=["Iran", "US"]
  y=["Tehran", "Washington DC"]
  z=[x,y]
  puts z
  y[0]="Isfahan"
  y[1]="Chicago"
  puts z
  y=["Shiraz", "Santa Barbara"]
  puts z

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