Thread: Help with queues

All objects are constructed using the object constructer (well, almost all. certain objects hide their constructors and have you call a factory constructor). To do so, you use the "new" keyword and the class name.

Unfortunately, those classes are not part of the standard Java API, so I'm just guessing at how they are to be used. I am going under the assumption that all of them implement the Queue Interface (this is a link the Java's SE API).

The Queue-type classes also require generic parameters. This is to tell Java what type of object this queue is allowed to hold. These are passed through the <>.

It is important to note that generics need to be classes, so you can't simply pass in "int", which is a primitive data type.

new ArrayQueue<int>(); // Error! int is a primitive data type!

Here's a simple snippet to show how to construct an ArrayQueue of Integers the correct way.

// create a new ArrayQueue
ArrayQueue<Integer> myArrayQueue = new ArrayQueue<Integer>();

There are two simple ways to generate random numbers (well, actually creating your own isn't too hard but I'm going to ignore this option for now), but the easier way is to use a Random object. Simply create a Random object, and then use the nextInt() method to generate a Random number between 0 and the number you pass as a parameter.

// generate a random number from 0 - 10. Includes 0, but not 10
Random myGenerator = new Random();
myGenerator.nextInt(10);

To add items to the queue, you can use the offer() method. This tries to add an element to the queue, and returns true/false depending on if it succeeded or failed respectively. To remove items, use the remove() method. This will automatically remove the item most recently added.

// add a few Integers and remove them
ArrayQueue<Integer> myQueue1 = new ArrayQueue();
myQueue1.offer(5);
myQueue1.offer(4);
System.out.println("The first item you added was " + myQueue1.remove());
System.out.println("The second item you added was " + myQueue1.remove());

Obviously, for 100000 items you will want to use a for loop. To see how to use for-loops, see The for Statement(The Java Tutorials).