Friday, September 23, 2011
Thursday, September 22, 2011
Learn Core JAVA in Easy Steps [Page 3]
JAVA Data Types :-
(1) Primitive :
1. Integral
2. Boolean
3. Floating
(2) Reference :
1. Object
2. String
- byte: The
byte
data type is an 8-bit signed two's complement integer. It has a minimum value of -128 and a maximum value of 127 (inclusive). Thebyte
data type can be useful for saving memory in large arrays, where the memory savings actually matters. They can also be used in place ofint
where their limits help to clarify your code; the fact that a variable's range is limited can serve as a form of documentation. - short: The
short
data type is a 16-bit signed two's complement integer. It has a minimum value of -32,768 and a maximum value of 32,767 (inclusive). As withbyte
, the same guidelines apply: you can use ashort
to save memory in large arrays, in situations where the memory savings actually matters. - int: The
int
data type is a 32-bit signed two's complement integer. It has a minimum value of -2,147,483,648 and a maximum value of 2,147,483,647 (inclusive). For integral values, this data type is generally the default choice unless there is a reason (like the above) to choose something else. This data type will most likely be large enough for the numbers your program will use, but if you need a wider range of values, uselong
instead. - long: The
long
data type is a 64-bit signed two's complement integer. It has a minimum value of -9,223,372,036,854,775,808 and a maximum value of 9,223,372,036,854,775,807 (inclusive). Use this data type when you need a range of values wider than those provided byint
.
- float: The
float
data type is a single-precision 32-bit IEEE 754 floating point. Its range of values is beyond the scope of this discussion, but is specified in section 4.2.3of the Java Language Specification. As with the recommendations forbyte
andshort
, use afloat
(instead ofdouble
) if you need to save memory in large arrays of floating point numbers. This data type should never be used for precise values, such as currency. For that, you will need to use the java.math.BigDecimal class instead.Numbers and Strings coversBigDecimal
and other useful classes provided by the Java platform. - double: The
double
data type is a double-precision 64-bit IEEE 754 floating point. Its range of values is beyond the scope of this discussion, but is specified in section4.2.3 of the Java Language Specification. For decimal values, this data type is generally the default choice. As mentioned above, this data type should never be used for precise values, such as currency. - boolean: The
boolean
data type has only two possible values:true
andfalse
. Use this data type for simple flags that track true/false conditions. This data type represents one bit of information, but its "size" isn't something that's precisely defined. - char: The
char
data type is a single 16-bit Unicode character. It has a minimum value of'\u0000'
(or 0) and a maximum value of'\uffff'
(or 65,535 inclusive).
Data Type Default Value (for fields) byte 0 short 0 int 0 long 0L float 0.0f double 0.0d char '\u0000' String (or any object) null boolean false
Learn Core JAVA in Easy Steps [Page 2]
The Features / Buzz Words / Characteristics / Advantages of JAVA:
- Simple
- Secure
- Platform Independent
- Portable
- Object Oriented
- Robust
- Distributed
- Dynamic
- High Performance
- Multithreaded
- Interpreted
- Architecture Neutral
Object Oriented:
- Inheritance
- Encapsulation
- Polymorphism
- Abstraction/Dynamic binding
How to Create and Execute a Program in Core Java:
there are two ways:
1. without Integrated Development Environment (IDE)
2. with Integrated Development Environment (IDE)
1.without IDE
Create: write your program in notepad and save it with .java extension.
[make sure that all class names are starting with capital letter and your filename must be the classname which has the main method]
Execute: open command prompt and write javac filename.java [this will compile your java file] then write java filename [this will run your compiled file].
2.with IDE
Eclipse and NetBeans are most popular IDEs for JAVA.
[as we have TC-Turbo C in C and C++]
Wednesday, September 21, 2011
Learn Core JAVA in Easy Steps [Page 1]
Book: The JAVA Language Specification
James A. Gosling, OC (born May 19, 1955 near Calgary, Alberta, Canada) is a software developer. Between 1984 and 2010, Gosling was with Sun Microsystems, best known as the father of the Java programming language.
Java can run on any Hardware and Software interface. |
Three types of JAVA programs/softwares/applications :
1. Standalone/Simple Applications
2. Applets
3. Servlets (and jsp) - Web Applications