Thursday, December 13, 2007

Notes on Java Fundamentals

Basic Lexical elements----
--->keywords & other reserved words

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1. Access modifiers - private,public,protected
2.other modifiers---abstract,final,static,synchronized,transient, volatile
3 Name space keywords -- import,package

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byte,short,int,long-- signed two's complement integers
boolean -- 1 bit
char-- 16 bit unicode characters rather than ASCII set used in C

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Formula ------2^(n-1) to 2^(n-1)-1`

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Exceptional Floating point constants---

Float.NAN
(NAN Stands for Not A Number)
Float.NEGATIVE_INFINITY
Float.POSITIVE_INFINITY
Double.NAN
Double.NEGATIVE_INFINITY
Double.POSITIVE_INFINITY

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char represented in single quotes -
'\u0000'--- followed by four hexadecimal

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Integral can be decimal, hexadecimal or octal
Hexadecimal starts with 0x
Octals start with 0

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Floating point e or E stands for exponential value
eg 7e3 =7000

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note--> double x=77; is valid declaration as doublex =77D;

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To convert boolean, characters,integers,floating point numbers to String use valueOf() method
String is not null terminated.

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Once initialized string objects are inmutable i.e cannot change their contents. so use stringBuffer if the contents have to be changed.

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String bounds checked at run time rather than compile time.

string abc ="sdefg";
is not same as
string abc =new("string");

if we use first one compiler scans current cache to check for another string object with same literal value.
If it is there it reuses same object.

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1 comment:

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