Notes 17 - JavaOverview

Notes 17 - JavaOverview - Java Overview Taken from Core Web...

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1 Java Overview Taken from Core Web Programming Marty Hall, Larry Brown
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2 Java Source Code Java Bytecode Compiler ( javac ) Java Bytecode Execution JIT Compiler or Interpreter Compile Time Run Time Java is Cross-Platform? • Truth: Java programs can compile to machine-independent bytecode • Truth: All major operating systems have Java runtime environments – Most bundle it (Solaris, MacOS, Windows)
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3 Truth: Java has a portable graphics library AWT (Java 1.0 and 1.1) was weak. JFC/Swing (Java 2) much more complete and powerful. Java is Cross-Platform?
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4 Java is Cross-Platform? Myth: Write Once Run Anywhere – Cross-platform code can be achieved, but you must test on all platforms you will deliver on. • Java applications can execute local code • The graphics library behaves slightly differently on different platforms
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5 Java is Simple? • Java greatly simplifies several language features – Java has automatic memory management • No dangling pointers. No memory leaks. • A problem for real-time programs – Java simplifies pointer handling • No explicit reference/dereference operations • Everything is a pointer (like Lisp) – No makefiles – No header files – C++ syntax streamlined
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6 Java is Powerful? Java has a rich set of standard libraries – Networking – Threads (lightweight processes) – Distributed objects – Database access – Graphics: GUI controls and drawing – Data structure library – Arbitrary precision integral and fixed-point arithmetic – Digital signatures – Serialization (transmitting/reassembling data structures) – File and stream compression
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7 Key Java Packages and Protocols Core Technologies – JDBC – RMI – Jini (Device Networking) – JavaBeans – Swing – Java 2D Standard Extensions – Servlets and JavaServer Pages (JSP) – Enterprise Java Beans – Java 3D
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8 Java Packages and Protocols: JDBC (Java DataBase Connectivity) Standardizes mechanism for making connection to database server – Requires server-specific driver on client. No change to server. Standardizes mechanism for sending queries – Either regular or parameterized queries (stored procedures) Standardizes data structure of query result – Assumes relational data, so data structure is a table Does not standardize SQL syntax – Queries are simply strings – Server extensions and enhancements supported
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9 Java Packages and Protocols: JavaBeans JavaBeans is to Java as ActiveX is to Visual C++. – Lets you package a Java program as a software “component” – Visual tools can modify/manipulate it without knowing anything about it in advance – Better security and portability than ActiveX – But more ActiveX components available
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10 Java Packages and Protocols: Swing Standard GUI-control (widget) library in Java 2 Many more built-in controls Much more flexible and customizable Includes many small features aimed at commercial applications
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Notes 17 - JavaOverview - Java Overview Taken from Core Web...

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