Why Java API Is Needed

Sorting Algorithm Tutorials - Herong's Tutorial Examples

∟Why Java API Is Needed

This section describes why Java API is needed for sorting algorithms The Java API (Application Programming Interface) is needed to provide a single standard calling interface for all Java applications that want to use the sorting algorithm.

When a sorting algorithm is implemented as a function in a particular programming language, it must interface with the application program that needs this function. So before writing an implementation of a sorting algorithm, we need to define the Application Programming Interface (API), to answer the following questions:

What are the requirements on the data elements to be sorted?
How to perform a comparison between two data elements?
How the collection of data elements to be sorted should be defined?
How the sorting algorithm should be invoked?

JDK (Java Development Kit) provides a very good API for implementing sorting algorithms in Java. It can be summarized as:

Data elements to be sorted should be instances of a class that implements the Comparable interface.
Comparable interface requires one instance method called compareTo(Object d), which returns: 1. A positive integer, if this object is in higher order than d; 2. Zero, if this object is in equal order as d; 3, A negative integer, if this object is in lower order as d.
The collection of data elements should be stored in an array as: Object[].
Sorting algorithms should be implemented as static methods as: sort(Object[] a, int fromIndex, int toIndex), where "fromIndex" is inclusive, and "toIndex" is exclusive.