Java-Whitepaper Essay Example for Free

deep brown-White typography EssayThis white paper comp ars C++/Qt with chocolate/AWT/ dribble for developing large-scale, real-world softwargon with pictorial substance ab roler interfaces. References be made to single-handed reports that examine various aspects of the two toolsets. 1 A equivalence of Qt and coffee 1. What Do We Comp ar? When selecting an environment for a large softw atomic number 18 victimisation project, there are mevery aspects that must be considered.The schedule speech communication is superstar of the most signifi merchantmant aspects, since its choice has considerable impact on what separate options are available. For example, in a graphical user interface development project, developers will need a GUI library that provides made user interface components, for example, only iftons and menus. Since the selection of the GUI library itself has a large impact on the development of a project, it is non uncommon for the GUI library to be chosen first, with the platformming spoken communication macrocosm determined by the languages for which the library is available.Usually, there is tho one language per library. Other software components bid database access libraries or communication libraries must also be taken into consideration, merely they rarely fox such a strong impact on the overall design as the GUI libraries. In this white paper, the objective is to compare the C++/Qt environment with the Java/AWT/Swing environment. In order to do this in the most useful way, we will begin by comparing the programming languages involved, i. e. C++ and Java, and therefore compare the two GUI libraries, Qt for C++ and AWT/Swing for Java. 2. Comparing C++ and Java When discussing the various benefits and drawbacks of situation programming languages, the debate often degenerates into arguments that are based on individualized come and preference instead than both objective criteria. Personal preferences and experience sh ould be taken into account when selecting a programming language for a project, but because it is subjective, it provide non be considered here.Instead we will look at issues such as coder-efficiency, runtime-efficiency and repositing-efficiency since these shadow be quantified and encounter been examined in scientifically conducted research, although we will also incorporate in set upion based on the practical exerience of projects that pick up been utilise in our own company. 2. 1. Programmer-efficiency Programmer-efficiency describes how efficiently (i. e. how quickly and accurately) a programmer with a given degree of experience and knowledge can appliance a certain set of requirements in a particular programming language, including debugging and project setup time.Since developer salaries are one of the primary cost factors for any programming project, programmer-efficiency greatly affects the 2 A Comparison of Qt and Java cost-efficiency of the project. To some exten t, programmer-efficiency is also determined by the tools available. The main design goal of Java is increase programmer-efficiency compared to other general-purpose programming languages, rather than increased entrepot- or runtime-efficiency. Java has several features designed to make it more than programmer-efficient.For example, un uniform C++ (or C), the programmer does not have to explicitly free (give back) allocated depot resources to the operating dust. Freeing clean memory (garbage hookup) is handled automatically by the Java runtime system, at the expense of memory- and runtime-efficiency (see below). This liberates the programmer from the burden of keeping track of allocated memory, a tedious lying-in that is a major(ip) cause of bugs. This feature alone should significantly increase the programmer-efficiency of Java programmers, compared to C++ (or C) programmers. seek installs that in practice, garbage assembly and other Java features, do not have a major influe nce on the programmer-efficiency. One of the classic software estimation models, Barry Boehms CoCoMo1 predicts the cost and schedule of a software project using cost drivers which take into account variables like the general experience of a programmers, the experience with the programming language in question, the targeted reliability of the program, etc. Boehm writes that the amount of effort per source tale was highly independent of the language level.Other research, for example, A order of programming measurement and estimation by C. E. Walston and C. P. Felix of IBM2, forelands in the same direction. Both the reports cited here pre-date the advent of Java by many years, although they be to give away a general principle that the sophistication of a general-purpose programming language has, compared with other aspects, like the experience of the developers, no significant influence on the overall project costs. There is more new-fashioned research that explicitly includes Ja va and which supports this hypothesis.In An empirical comparison of C, C++, Java, Perl, Python, Rexx, and Tcl3, Lutz Prechelt of the University of Karlsruhe, describes an experiment he conducted in which computer science students were assigned a particular design and development task and asked to go through the spec provided in any of the languages C, C++, or Java which they could freely choose according to their personal preferences (the other languages were examined in a different part of the research project). The data gathered shows intimately the same results for C++ and Java (with C rivulet third in most aspects).This is also backed up by our own experience if programmers can choose their favorite programming language (which is unremarkably the one they have most experience of), programmers with the same level of experience (measured for example, in years of programming experience in general) achieve closely the same programmer-efficiency. Another interesting aspect that we noted (but which is not yet back up by any formal 3 A Comparison of Qt and Java research) is that less experienced developers seem to achieve somewhat better results with Java, medium-experienced developers achieve about the same results with twain programming languages, nd experienced developers achieve better results with C++. These findings could be due to better tools being available for C++ til now this is an aspect that must be taken into account. An interesting way to quantify programmer-efficiency is the Function Point method developed by Capers Jones. Function points are a software metric that only depend on the functionality, not on the carrying out. Working from the function points, it is accomplishable to compute the lines of code needed per function point as well as the language level which describes how many function points can be implemented in a certain amount of time.Intriguingly, both the values for the lines of code per function point and the language lev el are identical for C++ and Java (6 for the language level, compared with Cs 3. 5 and Tcls 5, and 53 for the lines of code per function point, compared with Cs 91 and Tcls 64). In conclusion both research and practice contradict the claim that Java programmers achieve a higher programmer-efficiency than C++ programmers. 2. 2. Runtime-efficiency We have seen that Javas programmer-efficiency appears to be illusory. We will now examine its runtime efficiency. Again, Prechelt provides useful data.The amount of data he provides is broad, but he arrives at the conclusion that a Java program must be anticipate to run at to the lowest degree 1. 22 times as long as a C/C++ program. Note that he says at least the average runtime of Java programs is even longer. Our own experience shows that Java programs tend to run about 2-3 times as long than their equivalent weight C/C++ programs for the same task. Not surprisingly, Java loses even more ground when the tasks are CPU-bound. When it come s to programs with a graphical user interface, the increased latency of Java programs is worse than the runtime performance hit.Usability studies show that users do not mete out about whether a long running task takes, say, two or three minutes, but they do care when a program does not show an immediate reaction to their interaction, for example when they press a exit. These studies show that the limit of what a user accepts before they consider a program to be unresponsive can be as little as 0. 7 seconds. Well return to this issue when we compare graphical user interfaces in Java and C++ programs. An explanation about wherefore Java programs are slow than C++ is in order.C++ programs are stack upd by the C++ compiler into a binary format that can be con joinmated directly by the CPU the whole program doing gum olibanumly takes get in 4 A Comparison of Qt and Java hardware. (This is an oversimplification since most modern CPUs execute microcode, but this does not affect th e issues discussed here. ) On the other hand, the Java compiler compiles the source code into bytecode which is not executed directly by the CPU, but rather by another piece of software, the Java virtual(prenominal) Machine (JVM). The JVM in turn, runs on the CPU.The execution of the bytecode of a Java program does not take place in (fast) hardware, but instead in (much slow) software emulation. Work has been undertaken to develop Just in age (JIT) compilers to address Javas runtime efficiency problem, but no universal solution has yet emerged. It is the semi-interpreted temper of Java programs that makes the compile once, run anywhere approaching of Java possible in the first place. once a Java program is compiled into bytecode, it can be executed on any programme which has a JVM.In practice, this is not always the case, because of implementation differences in different JVMs, and because of the necessity to sometimes use native, non-Java code, usually written in C or C++, tog ether with Java programs. But is the use of platform-independent bytecode the recompense approach for crossplatform maskings? With a good cross-platform toolkit like Qt and good compilers on the various platforms, programmers can achieve almost the same by compiling their source code once for for each one platform write once, compile everywhere.It can be argued that for this to work, developers need access to all the platforms they want to support, while with Java, in theory at least, developers only need access to one platform running the Java development tools and a JVM. In practice, no responsible software manufacturing business will ever certify their software for a platform the software hasnt been tested on, so they would smooth need access to all the relevant platforms. The question arises why it should be needful to run the Java Virtual Machine in software if a program can be implemented in software, it should also be possible to have hardware implement the same unctiona lity. This is what the Java designers had in mind when they developed the language they assumed that the performance penalty would depart as before long as Java CPUs that implement the JVM in hardware would become available. But aft(prenominal) five years, such Java CPUs have not become generally available. Java automatically de-allocates (frees) unused memory. The programmer allocates memory, and the JVM keeps track of all the allocated memory jampacks and the references to them. As soon as a memory block is no longer referenced, it can be reclaimed. This is done in a process called garbage array in which the JVM periodically checks all the allocated memory blocks, and removes any which are no longer referred to. Garbage collection is very convenient, but the trade offs are greater memory consumption and slower runtime speed.. With C++, the programmer can (and should) delete blocks of memory as soon as they are no longer required.With Java, blocks are not deleted until the nex t garbage collection run, and this depends on the implementation on the JVM being used. Prechtelt provides figures which state that on average ( ) and with a confidence of 80%, the Java programs consume at least 32 MB (or 297%) more memory than the C/C++ programs ( ). In addition to the higher memory requirements, the garbage collection process itself requires processing power which is consequently not available to the actual application functionality, leading to slower overall runtimes.Since the garbage collector runs periodically, it can occasionally lead to Java programs freezing for a few seconds. The best JVM implementations keep the occurrence of such freezes to a minimum, but the freezes have not been eliminated entirely. When dealing with out-of-door programs and devices, for example, during I/O or when interacting with a database, it is usually desirable to close the file or database partnership as soon as it is no longer required. Using C++s destructors, this happens as soon as the programmer calls delete.In Java, closing may not occur until the next garbage amass sweep, which at best may tie up resources unnecessarily, and at worst risks the fall in resources ending up in an inconsistent state. The fact that Java programs keep memory blocks around longer than is strictly necessary is especially problematic for embedded devices where memory is often at a premium. It is no coincidence that there is (at the time of writing) no complete implementation of the Java platform for embedded devices, only partial implementations that implement a subset.The main reason why garbage collection is more expensive than explicit memory management by the programmer is that with the Java scheme, information is lost. In a C++ program, the programmer knows both where their memory blocks are (by storing pointers to them) and knows when they are not needed any longer. In a Java 6 A Comparison of Qt and Java program, the latter information is not available to the JVM (e ven though it is known to the programmer), and thus the JVM has to manually find unreferenced blocks.A Java programmer can make use of their knowledge of when a memory block is not needed any longer by deleting all references that are still around and triggering garbage collection manually, but this requires as much effort on the part of the programmer as with the explicit memory management in C++, and still the JVM has to look at each block during garbage collection to determine which ones are no longer used. Technically, there is nothing that prevents the implementation and use of garbage collection in C++ programs, and there are commercial programs and libraries available that cracking this.But because of the disadvantages mentioned above, few C++ programmers make use of this. The Qt toolkit takes a more efficient approach to reliever the memory management task for its programmers when an object is deleted, all dependant objects are automatically deleted too. Qts approach does not interfere with the programmers freedom to delete manually when they wish to. Because manual memory management burdens programmers, C and C++ have been accused of being prone to generate unstable, bug-ridden software.Although the danger of producing memory corruption (which typically leads to program crashes) is sure as shooting higher with C and C++, good education, tools and experience can greatly reduce the risks. Memory management can be learned like anything else, and there are a large number of tools available, both commercial and open source, that help programmers ensure that there are no memory errors in the program for example, Insure++ by Parasoft, Purify by Rational and the open source Electric Fence.C++s flexible memory management system also makes it possible to write custom memory profilers that are adapted to whichever type of application a programmer writes. To sum up this discussion, we have found C++ to provide much better runtime- and memory-efficiency than Ja va, while having comparable programmer-efficiency. 2. 4. functional libraries and tools The Java platform includes an impressive number of packages that provide hundreds of classes for all kinds of purposes, including graphical user interfaces, security, networking and other tasks.This is certainly an advantage of the Java platform. For each package available on the Java platform, there is at least one corresponding library for C++, although it can be knockout to assemble the various libraries that would be needed for a C++ project and make them all work together correctly. However, this strength of Java is also one of its weaknesses. It becomes increasingly difficult for the individual programmer to find their way through the huge APIs. For any given task, you can be almost certain that somewhere, there is 7A Comparison of Qt and Java functionality that would accomplish the task or at least help with its implementation. But it can be very difficult to find the right package and t he right class. Also, with an increasing number of packages, the size of the Java platform has increased considerably. This has led to subsets e. g. , for embedded systems, but with a subset, the advantage of having everything readily available disappears. As an aside, the size of the Java platform makes it almost impossible for smaller manufacturers to ship a Java system independent from Sun Microsystems, Javas inventor, and this reduces competition.If Java has an advantage on the side of available libraries, C++ clearly has an advantage when it comes to available tools. Because of the considerable maturity of the C and C++ family of languages, many tools for all aspects of application development have been developed, including design, debugging, and profiling tools. While there are Java tools appearing all the time, they seldom measure up to their C++ counterparts. This is often even the case with tools with the same functionality coming from the same manufacturer compare, for exa mple, Rationals Quantify, a profiler for Java and for C/C++.The most important tool any developer of a compiled language uses, is still the compiler. C++ has the advantage of having compilers that are clearly superior in execution speed. In order to be able to ship their compilers (and other tools) on various platforms, vendors tend to implement their Java tools in Java itself, with all the aforementioned memory and efficiency problems. There are a few Java compilers written in a native language like C (for example, IBMs Jikes), but these are the exception, and seldom used. 3. Comparing AWT/Swing and QtSo far, we have compared the programming language Java and the programming language C++. But as we discussed at the beginning of this article, the programming language is only one of the aspects to consider in GUI development. We will now compare the packages for GUI development that are shipped with Java, i. e. AWT and Swing, with the cross-platform GUI toolkit, Qt, from the Norwegia n supplier, Trolltech. We have confined the comparision on the C++ side to the Qt GUI toolkit, since unlike MFC (Microsoft basis Classes) and similar toolkits, This seems to contradict Javas cross-platform philosophy and may be due to the the initial AWT adaption being reputedly developed in under fourteen days. Because of these and a number of other problems with the AWT, it has since been augment by the Swing toolkit. Swing relies on the AWT (and consequently on the native libraries) only for very prefatory things like creating rectangular windows, handling events and executing primitive sketch operations. Everything else is handled within Swing, including all the drawing of the GUI components.This does away with the problem of applications looking and behaving differently on different platforms. Unfortunately, because Swing is mostly implemented in Java itself, it lacks efficiency. As a result, Swing programs are not only slow when performing computations, but also when drawi ng and handling the user interface, leading to poor responsiveness. As mentioned earlier, poor responsiveness is one of the things that users are least willing to tolerate in a GUI application. On todays standard commodity hardware, it is not unusual to be able to watch how a Swing button is redrawn when the mouse is pressed over it.While this situation will surely improve with faster hardware, this does not address the fundamental problem that complex user interfaces developed with Swing are inherently slow. The Qt toolkit follows a similar approach like Swing, it only relies on the native libraries only for very basic things and handles the drawing of GUI components itself. This brings Qt the same advantages as Swing (for example, applications look and behave the same on different platforms), but since Qt is entirely implemented in C++ and thus compiled to native code it does not have Swings efficiency problems.User interfaces written with Qt are typically very fast because of Qts smart use of caching proficiencys, they are sometimes even faster than comparable programs written using only the native libraries. Theoretically, an optimum native program should always be at least as fast as an equivalent optimal Qt program however, making a native program optimal is much more difficult and requires more programming skills than making a Qt program optimal. Both Qt and Swing employ a styling technique that lets programs display in any one of a number of ardours, independent of the platform they are running on.This is possible because both Qt and Swing handle the drawing themselves and can draw GUI elements in whichever style is desired. Qt even ships with a style that emulates the default look-and-feel in Swing programs, along with styles that emulate the 9 A Comparison of Qt and Java Win32 look-and-feel, the Motif look-and-feel, andin the Macintosh version the MacOS X Aqua style. 3. 2. Programming Paradigms In Qt and Swing While programming APIs to some extent a re a matter of the programmers personal taste, there are some APIs that lend themselves to simple, short, and elegant application code far more readily than others.