Sunday, 31 July 2011

Java Data Types

Java programming language is a language in which all the variables must be declared first and then to be used. That means to specify the name and the type of the variable. This specifies that Java is a strongly-typed programming language. Like
  int pedal = 1;
This shows that there exists a field named 'pedal' that holds a data as a numerical value '1'. The values contained by the variables determines its data type and to perform the operations on it.
There are seven more primitive data types which are supported by Java language programming in addition to int. A primitive data type is a data type which is predefined in Java. Following are the eight primitive data types:
It is a 32-bit signed two's complement integer data type. It ranges from -2,147,483,648 to 2,147,483,647. This data type is used for integer values. However for wider range of values use long.
The byte data type is an 8-bit signed two's complement integer. It ranges from -128 to127 (inclusive). We can save memory in large arrays using byte. We can also use byte instead of int  to increase the limit of the code.
The short data type is a 16-bit signed two's complement integer. It ranges from -32,768 to 32,767. short is used to save memory in large arrays.
The long data type is a 64-bit signed two's complement integer. It ranges from -9,223,372,036,854,775,808 to 9,223,372,036,854,775,807. Use this data type with larger range of values. 
The float data type is a single-precision 32-bit IEEE 754 floating point. It ranges from 1.40129846432481707e-45 to 3.40282346638528860e+38 (positive or negative). Use a float (instead of double) to save memory in large arrays. We do not use this data type for the exact values such as currency. For that we have to use java.math.BigDecimal class.
This data type is a double-precision 64-bit IEEE 754 floating point. It ranges from 4.94065645841246544e-324d to 1.79769313486231570e+308d (positive or negative). This data type is generally the default choice for decimal values.
The boolean data type is 1-bit  and has only two values: true and false. We use this data type for conditional statements. true and false are not the same as True and False. They are defined constants of the language.
The char data type is a single 16-bit, unsigned Unicode character. It ranges from 0 to 65,535. They are not same as ints, shorts etc.
The following table shows the default values for the data types:
 Keyword  Description   Size/Format
 byte  Byte-length integer  8-bit two's complement
 short   Short integer  16-bit two's complement
 int  Integer   32-bit two's complement
 long   Long integer   64-bit two's complement
 float  Single-precision floating point  32-bit IEEE 
 double  Double-precision floating point  64-bit IEEE 
 char   A single character   16-bit Unicode character
 boolean   A boolean value (true or false)   true or false
When we declare a field it is not always essential that we initialize it too. The compiler sets a default value to the fields which are not initialized which might be zero or null. However this is not recommended. 
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