An interesting description of encapsulation was recently given in another internet.com article By Rocky Lhotka regarding VB.NET.  That description reads as follows:

"Encapsulation is the concept that an object should totally separate its interface from its implementation. All the data and implementation code for an object should be entirely hidden behind its interface. The idea is that we can create an interface (Public methods in a class) and, as long as that interface remains consistent, the application can interact with our objects. This remains true even if we entirely rewrite the code within a given method thus the interface is independent of the implementation."

In non-trivial computing problems you often need to store lists of items. Often these items can be specified sequentially and referred to by their position in the list. Sometimes this ordering is natural as in a list of the first ten people to arrive at a sale. The first person would be item one in the list, the second person to arrive would be item two, and so on. Other times the ordering doesn't really mean anything such as in the ram configuration problem of the previous chapter where having a 4 MB SIMM in slot A and an 8 MB SIMM in slot B was effectively the same as an 8 MB SIMM in slot A and a 4 MB SIMM in slot B. However it's still convenient to be able to assign each item a unique number and enumerate all the items in a list by counting out the numbers.

You don't have to stop with two dimensional arrays. Java lets you have arrays of three, four or more dimensions. However chances are pretty good that if you need more than three dimensions in an array, you're probably using the wrong data structure. Even three dimensional arrays are exceptionally rare outside of scientific and engineering applications. The syntax for three dimensional arrays is a direct extension of that for two-dimensional arrays. Here's a program that declares, allocates and initializes a three-dimensional array

Now that we've learned how to properly swap the values of two variables, let's proceed to sorting. There are many different sorting algorithms. One of the simplest and the most popular algorithms is referred to as bubble sort. The idea of bubble sort is to start at the top of the array. We compare each element to the next element. If its greater than that element then we swap the two. We pass through the array as many times as necessary to sort it. The smallest value bubbles up to the top of the array while the largest value sinks to the bottom. (You could equally well call it a sink sort, but then nobody would know what you were talking about.)

The last chapter was rooted solidly in the 1970's. It used techniques often referred to as "structured" or "procedural programming" which were popular then. (We skipped right over the most popular innovation of the 60's and the Basic programmer, spaghetti code). Certain programmers are sometimes said to "Write Fortran in any language," and that's more or less what we did. You now have the knowledge to accomplish with Java anything that can be done within the bounds of ANSI-standard Fortran 77.