14.jun.2012

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14.jun.2012

  1. 1. 1
  2. 2. Discussion about???Why need to navigate to Java code life cycleJAVA? Data types.Goals of JAVA. Wrapper Classes.Features of JAVA. Operators.C++ Vs JAVA. 2
  3. 3. Why ‘JAVA’ the programming language?The ultimate aim to develop the JAVA programming languageis to implement the words “write once; run anywhere, any time,forever”.This is the problem the people meet at that time. The wantedto have the language that can be run for any platform(OperatingSystem). This led to the development of JAVA as initial nameOak. Then JAVA COFFEE, finally renamed as JAVA. 3
  4. 4. cntd..... The application needed to be platform independent in some places. Assume the situation the application is going to be run on networked systems. In network many kind of system specification and OS may be there. In this case the application must be a Platform independent. Here, JAVA will help us. 4
  5. 5. Goal of JAVAIt should use the object-oriented programming methodology.It should allow the same program to be executed on multipleoperating systems.It should contain built-in support for using computer networks.It should be designed to execute code from remote sourcessecurely.It should be easy to use by selecting what was considered thegood parts of other object-oriented languages. 5
  6. 6. Features of JAVASimple Architecture-neutralSecure InterpretedPortable High performanceObject-oriented Automatic Garbage CollectionRobustMultithreaded 6
  7. 7. Automatic Garbage CollectionThe memory management(allocation and de-allocation) of anallocated object is done automatically.If the reference for the object is not available in program, thenthe JVM automatically de-allocates the memory for that object.If this is not done automatically, the programmer must do thecode to manage the memory(allocate and de-allocate).If not de-allocated by the programmer, then the memoryfragmentation is difficult. Memory leak will occur. 7
  8. 8. Example codepublic static int main(String[] a){ System.out.println(“n”+4+34); return 0;}Output???Error: Main method not found in class sample, please define the main method as: public static void main(String[] args) 8
  9. 9. eg: cntd public static void main(String[] a) { System.out.println(“n”+4+34); System.out.println(34+2+"n"); return 0; } Output ??? 434 36 public static void main(String[] a) { System.out.println(4+34); return 0; } Output ??? 38 9
  10. 10. C++ Vs C++ JAVANot a full-fledged object oriented The pure Object oriented language.language. Because, we can write thecomplete program without usingclass.We can write an error free program, Here, we can not complete thewith class and without having any execution without having code withincode within the main(). The program the main().can be correctly executed completely.Multiple inheritance is supported. Multiple inheritance is removed.Operator overloading is available. Not available. cntd…. 10
  11. 11. Virtual functions is available. Indirectly method overriding having the working of virtual function.Pointers, references available. References only available.Platform dependent. Platform independent.Abstract class avail. Abstract class may be mapped to Interface.Automatic garbage collection not avail. Available.Not a strongly typed language. Strongly typed language.Unicode not supported. Unicode support provided.Destructor available. finalize() method available instead destructor.const final 11
  12. 12. Function prototypeIn C++ the function prototype is ?? return_type function_name(argument_list)In java for the function prototype concentration on 4 things.return_type function_name(argument_list) Exception 12
  13. 13. Code Life cycle 13
  14. 14. Data TypesAll the data types available in C++ available in JAVA. But somemore additions upgraded.The data width of int and char are upgraded as follows.,The extra data types are also introduced. Data type Size(bits) long 64 int 32 short 16 char 16 New byte 8 boolean 1 14
  15. 15. Wrapper ClassesWrapper classes are special type of classes those bind with the simpletypes(Built-in data types).The Number class is an abstract class that defines a super class that isimplemented by the classes that wrap the numeric types(byte, int,float, double, long, short).The class name starts with the uppercase., like Integer, Float.Each and every wrapper class defines its own methods and constantdata members. The constant data members declared with the namesfull of uppercases. eg., Integer.MIN_VALUE. 15
  16. 16. for examplepublic static void main(String[] arg){ Integer g; g=45; System.out.println("ng : “+g);}Output 45 16
  17. 17. OperatorsThe operators used in C++ all supported in JAVA too.The I/O stream operators is not possible in java(<<,>>). Butthese operators used as a bitwise operators.Operator overloading can not be done by the user. But inJAVA, there are some implemented provisions those using thepre-defined operators with the class.The arithmetic, relational operators used with the String classobjects. 17
  18. 18. example…..public static void main(String[] arg){ String fg=“PSG",gh=“Psg"; if((fg+=gh)==fg) System.out.println("same....n"); else System.out.println(“Not same....n");} Output: same.... 18
  19. 19. Examplepublic static void main(String[] arr){ int i1=45; int i2=34; System.out.println(“Ans is : “+i1+i2);}Output??? Ans is : 4534 19
  20. 20. General examplepublic static void main(String[] arg){ DataInputStream inp=new DataInputStream(System.in); String mine=inp.readLine();}output??? Error: Un handled Exception IOException 20
  21. 21. Revisedpublic static void main(String[] arg) throws IOEception{ DataInputStream inp=new DataInputStream(System.in); String mine=inp.readLine(); System.out.println(“nString is : ”+mine); float h=Float.parseFloat(inp.readLine()); System.out.println(“n Float values is : ” +h);} 21
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