Month: May 2006

Java in Notes/Domino Explained: Operators


Java has a series of operators that can make the code less verbose, quicker to write and more readable. Below is a table of the most commonly used operators and an explanation of how to use them. At the bottom of the post you’ll find all the code if you want to play around with it.

Operator Description
== Test for object reference equality or equality of primitive data types.

int i=1;
int j=1;
System.out.println(i == j);
Output: true

String s1 = "lekkim";
String s2 = "lekkimworld";
System.out.println(s1 == s2);
Output: false

System.out.println(s1 == s1);
Output: true
!= Test for object reference non-equality or non-equality of primitive data types.

int i=1;
int j=2;
System.out.println(i != j);
Output: true

String s1 = "lekkim";
String s2 = "lekkimworld";
System.out.println(s1 != s2);
Output: true

System.out.println(s1 != s1);
Output: false
&& Logical AND operator.

boolean b1 = true;
boolean b2 = true;
System.out.println(b1 && b2);
Output: true
|| Logical OR operator.

boolean b1=true;
boolean b2=false;
System.out.println(b1 || b2);
Output: true
++ This operator can mean two things depending on which side of the variable the operator is on.

If the operator is to the right of the variable it means to use the value of the variable, increment the value and then store result back in the same variable. 

int i=0;
System.out.println("i=" + (i++));
Output: i=0
System.out.println("i=" + (i++));
Output: i=1

If the operator is to the left of the variable it means that the JVM should increment the variable, use the variable and store the result back in the variable.

int i=0;
System.out.println("i=" + (++i));
Output: i=1
System.out.println("i=" + (++i));
Output: i=2

Much used in for-loops:

for (int i=0; i<3; i++) {
  System.out.print(i + " ");
}
Output: 0 1 2
— Same as ++ but subtracting instead of incrementing.

int k=2;
System.out.println("k=" + (k--));
Output: k=2
System.out.println("k=" + (k--));
Output: k=1

int k=2;
System.out.println("k=" + (--k));
Output: k=1
System.out.println("k=" + (--k));
Output: k=0

Can also be used in for-loops:

for (int i=2; i>=0; i--) {
  System.out.print(i + " ");
}
Output: 2 1 0
+= Evaluate the + operator using the value in the variable on the left hand side and the right hand side and store result back in the same variable.

String s1 = "Mikkel";
s1 += " ";
s1 += "Heisterberg";
System.out.println("s1=" + s1);
Output: s1=Mikkel Heisterberg
-= Evaluate the – operator using the value in the variable on the left hand side and the right hand side and store result back in the same variable.

int i=10;
int k=5;
i -= k;
System.out.println("i=" + i);
Output: i=5

Below is the code for the above examples if you want to play around with it:

public class Main {

   public static void main(String[] args) {
      equal_equal();
      exclamation_equal();
      ampersand_ampersand();
      pipe_pipe();
      plus_plus1();
      plus_plus2();
      plus_plus3();
      minus_minus1();
      minus_minus2();
      minus_minus3();
      plus_equal();
      minus_equal();
   }

   public static void equal_equal() {
      int i=1;
      int j=1;
      System.out.println(i == j);

      String s1 = "lekkim";
      String s2 = "lekkimworld";
      System.out.println(s1 == s2);
      System.out.println(s1 == s1);
   }

   public static void exclamation_equal() {
      int i=1;
      int j=2;
      System.out.println(i != j);

      String s1 = "lekkim";
      String s2 = "lekkimworld";
      System.out.println(s1 != s2);
      System.out.println(s1 != s1);
   }

   public static void ampersand_ampersand() {
      boolean b1 = true;
      boolean b2 = true;
      System.out.println(b1 && b2);
   }

   public static void pipe_pipe() {
      boolean b1=true;
      boolean b2=false;
      System.out.println(b1 || b2);
   }

   public static void plus_plus1() {
      int i=0;
      System.out.println("i=" + (i++));
      System.out.println("i=" + (i++));
   }

   public static void plus_plus2() {
      int i=0;
      System.out.println("i=" + (++i));
      System.out.println("i=" + (++i));
   }

   public static void plus_plus3() {
      for (int i=0; i=0; i--) {
         System.out.print(i + " ");
      }
      System.out.println("");
   }

   public static void plus_equal() {
      String s1 = "Mikkel";
      s1 += " ";
      s1 += "Heisterberg";
      System.out.println("s1=" + s1);
   }

   public static void minus_equal() {
      int i=10;
      int k=5;
      i -= k;
      System.out.println("i=" + i);
   }
}

Address Picker on the web

For a customer project I need an address picker for the web. Instead of starting to build one from scratch myself I looked a little around and found one in the R6 NAB with a little help from the forum at developerWorks.

This just raises the question whether one is allowed, license-wise, to reuse components from the templates supplied by Lotus… Anyone who knows?

Comments feed for lekkimworld

Recently I was asked whether I had a comments feed to lekkimworld which I didn’t at the time, but I have created one. The feed isn’t perfect since the name of the comment author is missing but it is a start. I’m working on improving it.

You can access the comments feed using the following link.

Parle vous Domino?

I find it refreshing when someone chooses to blog in their native language when it isn’t English. I recently became aware of Julien Bottemanne who is blogging in French. Another example of “native blogging” is Thomas Adrian who is blogging in Swedish.

So please help me welcome Julien Bottemanne to the Domino blogosphere (I think Thomas is well known already). It seems like Julien is doing a fair amount of blogging on Notes/Domino and has been doing so for amount a year. You can find Juliens blog at www.domlike.net.

Welcome…