Know Your Java

Java is special Java source code Byte code/ native code Object code on windows Object code on Dos Object code on Lynux

Java Development Kit It contains  Java Tools  API (Application Programming Interface)/ Class Library

Java tools  javac – compiler  java – interpreter  javap – disassembler  jdb – debugger  javah – header  javadoc – for HTML programs  java applet viewer

Learning more about tools  javac compiles source code to byte code/ native code  java further interpretes the byte code  disassembler gives back the source code from object code i.e. native code  debugger helps in removing the bugs from the program

Learning more about tools  javah helps in creating internal header files  javadoc enables programming through html documents  javaappletviewer enables to work with applets(applications on net)

Application Program Interface  java.lang – classes String, Math, etc  java.io – classes related to ip /op  java.applet – to support generate applets  java.net – to support classes for net operations  java.awt – abstract window tool kit It supports classes to create GUI It supports classes to create GUI

Application Program Interface  java.txt – supports text elements  java.math – supports mathematical functions  java.util – has utility classes like Date, Time, StringTokenizer

What is a wrapper class?  Wrapper classes are part of java’s standard library java.lang  These convert primitive data type in an object.  That is why primitive data type in lower case  Wrapper class name begins with upper case.

What is a wrapper class?  Wrapper class wraps a value of primitive type in an object  All the methods of the wrapper classes are static.  The Wrapper class does not contain constructors.  Once a value is assigned to a wrapper class instance it can not be changed, anymore.  These objects can use methods of these wrapper class. –E.g. parseInt is a method of class Integer

Important structure of wrapper classes in Java.lang Object CharacterNumber ByteIntegerShortLong FloatDouble VoidBoolean

Syntactical difference  Primitive data type –int a =5;  Wrapper class –Integer a = new Integer (5);  Converting primitive type to object –int aa =5; –Integer a = new Integer (aa);

Some Java Acronyms  jvm – java virtual machine  Name of java interpreter  jar – java archive files  Directly executable files from any environment  jdbc – java data base connectivity  Just the name of the feature  This feature of java makes it powerful programming medium on the net