Is Java Getting You Into Loops?

If you are new to the world of J2EE application development, then the concept of loops can be quite tricky for you. There are several developers who struggle everyday to understand loops right. Java supports several different kinds of loops and unwinding all of them is a requisite for a good Java developer. This post discusses the concept of loops in detail and introduces you to all major loops used in Java programming.

There are three major concepts that form the building blocks of Java programming. These are iteration, sequence and selection. The concept of sequence is comprehended well by majority of developers. When statements come one after another, it is known as a sequence. For instance, the following statements form a sequence:

System.out.println ("hey");
System.out.println ("goodbye");

Understanding the concept of selection is also fairly easy. All you need is an if/switch statement and you can exercise full control on your code. If you have been into development for quite some time, you must be well aware about the importance of if statements. All major development ventures are practically impossible without the use of if statements at the right instances.

Iteration is the final essential concept of J2EE application development, which will also be the centre of focus of this post. The basic concept of iteration deals with repetition of a sequence of statements in a loop, until a said condition is met. Once the condition is met, iteration terminates and the loop is closed.

There are several different types of loops brought into use in Java development. Some of the major and most commonly used loops are listed below:

While Loops: While loop is used for simply testing a condition that has been listed in the loop. If the condition is not true, the iteration will not continue any further. Here's an example:

int i = 1;

while (i <= 5)
{

System.out.println ("count: " + i);

i++; }

For Loops: This is the simplest of all loops. It uses the 'for' statement to complete the iteration process using a series of sequences. By default, a 'for' loop includes a counter which has a defined starting point and a defined ending point. Here is an instance:

// for loop, from 1 to 5rnfor (int i = 1; i <= 5; i++)
{

System.out.println ("count: " + i); }

Do-While Loops: This is a version of the while loop itself. It includes the use of two keywords- do and while. For instance:

int i = 1;
dorn{

System.out.println ("count: " + i);

i++; }rnwhile (i <= 5)

Termination of Loops:

At times, during the programming you have to abruptly terminate a loop before the statement is fulfilled. For this purpose, Java uses two conditions: break and continue.

Break: This keyword can be used in case you want an early termination of the loop. Consider the following example for a better understanding:

// Check to see if "yes" string is storedrnboolean foundYes = false;

for (int i = 0; i < array.length; i++)
{

if (array[i].equals("yes"))

{

foundYes = true;

break;

} }

Continue: This keyword, unlike break, doesn't break the loop. Instead, it skips the loop and moves onto another iteration in the programming. Consider the following example:

for (int i = 0; i < array.length; i++)
{

if (array[i] == null)

// skip this one, goto next loop

continue;

else

{

// do something with array[i] ...

} }

The concept of loops is worth understanding if you want to make your J2EE application development worthwhile.