Introduction To Java Programming

The authors of Java have written an influential White Paper that explains their design goals and accomplishments. They also published a shorter summary that is organized along the following 11 buzzwords:

(01) Simple
(02) Object Oriented
(03) Network-Savvy
(04) Robust
(05) Secure
(06) Architecture Neutral
(07) Portable
(08) Interpreted
(09) High Performance
(10) Multithreaded
(11) Dynamic

(01 ) Simple

We wanted to build a system that could be programmed easily without a lot of eso-teric training and which leveraged today’s standard practice. So even though we found that C++ was unsuitable, we designed Java as closely to C++ as possible in order to make the system more comprehensible. Java omits many rarely used, poorly understood, confusing features of C++ that, in our experience, bring more grief than benefit.

Another aspect of being simple is being small. One of the goals of Java is to enable the construction of software that can run stand-alone in small machines. The size of the basic interpreter and class support is about 40K bytes; adding the basic standard libraries and thread support (essentially a self-contained microkernel) adds an additional 175K.

(02) Object Oriented

Simply stated, object-oriented design is a technique for programming that focuses on the data (= objects) and on the interfaces to that object. To make an analogy with carpentry, an “object-oriented” carpenter would be mostly concerned with the chair he was building, and secondarily with the tools used to make it; a “non-object-oriented” carpenter would think primarily of his tools. The object-oriented facilities of Java are essentially those of C++.

(03) Network-Savvy

Java has an extensive library of routines for coping with TCP/IP protocols like HTTP and FTP. Java applications can open and access objects across the Net via URLs with the same ease as when accessing a local file system.

(04) Robust

Java is intended for writing programs that must be reliable in a variety of ways. Java puts a lot of emphasis on early checking for possible problems, later dynamic (runtime) checking, and eliminating situations that are error-prone. . . . The single biggest difference between Java and C/C++ is that Java has a pointer model that eliminates the possibility of overwriting memory and corrupting data.

(05) Secure

Java is intended to be used in networked/distributed environments. Toward that end, a lot of emphasis has been placed on security. Java enables the construction of virus-free, tamper-free systems.

(06) Architecture Neutral

The compiler generates an architecture-neutral object file format—the compiled code is executable on many processors, given the presence of the Java runtime system. The Java compiler does this by generating bytecode instructions which have nothing to do with a particular computer architecture. Rather, they are designed to be both easy to interpret on any machine and easily translated into native machine code on the fly.

(07) Portable

Unlike C and C++, there are no “implementation-dependent” aspects of the specification. The sizes of the primitive data types are specified, as is the behavior of arithmetic on them.

The libraries that are a part of the system define portable interfaces. For example, there is an abstract Window class and implementations of it for UNIX, Windows, and the Macintosh.

(08) Interpreted

The Java interpreter can execute Java bytecodes directly on any machine to which the interpreter has been ported. Since linking is a more incremental and lightweight process, the development process can be much more rapid and exploratory.

(09) High Performance

While the performance of interpreted bytecodes is usually more than adequate, there are situations where higher performance is required. The bytecodes can be translated on the fly (at runtime) into machine code for the particular CPU the application is running on.

(10) Multithreaded

The benefits of multithreading are better interactive responsiveness and real-time behavior.

(11) Dynamic

In a number of ways, Java is a more dynamic language than C or C++. It was designed to adapt to an evolving environment. Libraries can freely add new methods and instance variables without any effect on their clients. In Java, finding out runtime type information is straightforward.