Ah the fun times of inputting data from the command line in a Java program.

Java has come a long way in this respect. From starting with IO Streams to what they have now. Currently, there is a Console class in the java.io package. Here’s a simple test I did capturing data the user enters:

import java.io.Console;
import java.io.IOException;

public class Test {

	public Test() {

	}

	public static void main(String[] args) throws IOException {
		String in = null;

		Console c = System.console();
		if (c == null) {
			System.err.println("No console.");
			System.exit(1);
		}

		while (!(in = c.readLine("> ")).equals(".quit")) {
			// do something with the content you just captured
			System.out.println(in);
		}
	}
}

That’s a very simple program now isn’t it? Just accepts whatever you enter and echos it back out to the screen. If you type in .quit it will quit the program.

So yep, just a simple program for capturing data in a Console application.

There are two types of for loops in Java. Your traditional loop:

for (int i = 0; i < 10; i++) {

}

Or the advanced loop that will loop through items in say an array:

for (String s : stringArray) {

}

Let's go through both of these examples and see what comes of it.

First, let's create a String Array for the loops to process.

String[] strArray = {"one", "two", "three"};

Simple enough. Just an array containing three values of one, two and three.

With the traditional for loop, you would loop through the array like this:

for (int i = 0; i < strArray.length; i++) {
    System.out.println(strArray[i]);
}

As you might have guessed, it outputs the three values:

One
Two
Three

Now, let's do the same thing, but using the other for loop. Sometimes this loop is called a For Each loop.

for (String s : strArray) {
    System.out.println(s);
}

Again we get the three values:

One
Two
Three

I prefer the new method myself. It comes in handy. But there are times that you'll want to use the traditional for loop, (for example if you want to run through a Multidensional Array).

Happy Coding!

I read in a C++ book once that you should have your own String Utils class file at your disposal.

Of course there are several people who have created a String Utils class out there on ther internet. Apache StringUtils comes to mind. But why not have something that you call your own?

Having programmed in ColdFusion for a number of years, I find that the left and right functions have been very useful. Of course there is nothing of the sort in Java.

So, here is my attempt at writing such methods.

The premise is simple. You take a string and specify how many characters from the left or from the right you wish to get from the string.

public class StringUtils {

    public String left(String str, int num) {
        return str.substring(0, num);
    }

    public String right(String str, int num) {
        return str.substring(str.length() - num);
    }
}

Now of course there are two ways that you can have your StringUtils accessed. Either by calling the class and the methods, like above, or by having the methods be static. The choice is yours.

Ah The first program that everyone tends to write when learning a new programming language is Hello World. So, what is Hello World? Hello World is a simple program that simplay outputs the words “Hello World”.

In Java we would write this as follows:

public class HelloWorld {

    public static void main(String[] args) {
        System.out.println("Hello World");
    }

}

It’s that simple. If you haven’t guessed yet, here’s the output of the file:

Hello World