Algorithms in Core java Core Java

Generic collection interfaces have a great advantage you only need to implement your algorithms once. For example, consider a simple algorithm to compute the maximum element in a collection. Traditionally, programmers would implement such an algorithm as a loop. Here is how you find the largest element of an array.

Of course, to find the maximum of an array list, you would write the code slightlydifferently.

What about a linked list? You don’t have efficient random access in a linked list, but you can use an iterator.

These loops are tedious to write, and they are just a bit error prone. Is there an off-byone error? Do the loops work correctly for empty containers? For containers with only one element? You don’t want to test and debug this code every time, but you also don’t want to implement a whole slew of methods, such as these:

That’s where the collection interfaces come in. Think of the minimal collection interface that you need to efficiently carry out the algorithm. Random access with get and set comes higher in the food chain than simple iteration. As you have seen in the computation of the maximum element in a linked list, random access is not required for this task. Computing the maximum can be done simply by iteration through the elements. Therefore, you can implement the max method to take any object that implements the Collection interface.

Now you can compute the maximum of a linked list, an array list, or an array, with a single method. That’s a powerful concept. In fact, the standard C++ library has dozens of useful algorithms, each of which operates on a generic collection. The Java library is not quite so rich, but it does contain the basics: sorting, binary search, and some utility algorithms.

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