Java Language Characteristics
• The portable, interpreted nature of Java impacts its performance. While the performance of interpreted Java code is better than scripting languages and fast enough for interactive applications, it is slower than traditional languages whose source code is compiled directly into the machine code for a particular machine. To improve performance, Just-In-Time compilers (JITs) have been developed. A JIT compiler runs concurrently with the Java Virtual Machine and determines what pieces of Java code are called most often.
• The bytecode portability is what enables Java to be transported across a network and executed on any target computer system. Java applets are small Java programs designed to be included in an HTML (HyperText Markup Language) Web document. HTML tags specify the name of the Java applet +and its Uniform Resource Locator (URL). The URL is the location on the Internet at which the applet bytecodes reside. When a Java-enabled Web browser displays an HTML document containing an applet tag, the Java bytecodes are downloaded from the specified location and the Java Virtual Machine interprets or executes the bytecodes. Java applets are what enable Web pages to contain animated graphics and interactive content.
• Because Java applets can be downloaded from any system, security mechanisms exist within the Java Virtual Machine to protect against malicious or errant applets.
• Java is an object-oriented programming language, borrowing heavily from Smalltalk, Objective C, and C++. It is characterized by many as a better, safer C++. Java uses C++ syntax and is readily accessible to the large existing C++ development community.
• Java, however, does not drag along the legacy of C. It does not allow global variables, functions, or procedures. With the exception of a few primitive data types like integers or floating-point numbers, everything in Java is an object.
• Object references are not pointers, and pointer manipulation is not allowed. This contributes to the general robustness of Java programs since pointer operations tend to be particularly nasty and bug-prone. Java also manages memory itself, thereby avoiding problems with allocation and deallocation of objects. It does not allow multiple inheritance like C++ does, but supports another type of reuse through the use of formal interface definitions.
• Java is similar enough to C and C++ that it already feels familiar to most of the existing programming community. But it is different enough in important ways (memory management and cross-platform portability) that it is worth it for programmers to switch to a new language.
المادة المعروضة اعلاه هي مدخل الى المحاضرة المرفوعة بواسطة استاذ(ة) المادة . وقد تبدو لك غير متكاملة . حيث يضع استاذ المادة في بعض الاحيان فقط الجزء الاول من المحاضرة من اجل الاطلاع على ما ستقوم بتحميله لاحقا . في نظام التعليم الالكتروني نوفر هذه الخدمة لكي نبقيك على اطلاع حول محتوى الملف الذي ستقوم بتحميله .
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