well Sharad,A variable's data type determines the values it may contain, plus the operations that may be performed on it
The Java programming language supports eight primitive data types. A primitive type is predefined by the language and is named by a reserved keyword. Primitive values do not share state with other primitive values.
Names in programs are either simple, consisting of a single identifier, or qualified, consisting of a sequence of identifiers separated by "." tokens .

Every declaration that introduces a name has a scope (§6.3), which is the part of the program text within which the declared entity can be referred to by a simple name.

Packages and reference types (that is, class types, interface types, and array types) have members (§6.4). A member can be referred to using a qualified name N.x, where N is a simple or qualified name and x is an identifier. If N names a package, then x is a member of that package, which is either a class or interface type or a subpackage.

Answered by satyaiitk , an ibibo Master, at 6:20 PM on May 19, 2008

well, Data Type
1. The Primitive Types
2. Default values for primitives and references
3. Literals
4. Surprise! Java lets you overflow
5. Shows default initial values
The type of value that a variable will hold is called a data type. As you ay imagine, different variables can be meant to hold different types of values. Each data type uses a Java keyword to be characterized. As a modern language, Java provides even more support for its traditional data types. To do this, a class was created for each data type. This allows you to get more information from a variable declared with the particular data type you want to use.

Answered by Saurabh , an ibibo Master, at 11:05 AM on May 18, 2008

The eight primitive data types supported by the Java programming language are:

* 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). The byte data type can be useful for saving memory in large arrays, where the memory savings actually matters. They can also be used in place of int 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 with byte, the same guidelines apply: you can use a short 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, use long 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 by int.

* 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 4.2.3 of the Java Language Specification. As with the recommendations for byte and short, use a float (instead of double) 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 covers BigDecimal 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 section 4.2.3 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 and false. 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).

Answered by Nagendra , an ibibo Master, at 4:33 PM on May 17, 2008

A variable's data type determines the values it may contain, plus the operations that may be performed on it
The Java programming language supports eight primitive data types. A primitive type is predefined by the language and is named by a reserved keyword. Primitive values do not share state with other primitive values.

The eight primitive data types supported by the Java programming language are:

* 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).

* 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).

Java's primitive data types are very similar to those of C. They include boolean, byte, short, int, long, float, double, and char. The boolean type has been added. However the implementation of the data types has been substantially cleaned up in several ways.

1. Where C and C++ leave a number of issues to be machine and compiler dependent (for instance the size of an int) Java specifies everything.
2. Java prevents casting between arbitrary variables. Only casts between numeric variables and between sub and superclasses of the same object are allowed.
3. All numeric variables in Java are signed.

Answered by Shobhit , an ibibo Master, at 7:40 PM on May 16, 2008

well Sharad
The eight primitive data types supported by the Java programming language are:

1) 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).

2) 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).
Java's primitive data types are very similar to those of C. They include boolean, byte, short, int, long, float, double, and char. The boolean type has been added. However the implementation of the data types has been substantially cleaned up in several ways.
1) Where C and C++ leave a number of issues to be machine and compiler dependent (for instance the size of an int) Java specifies everything.
2) Java prevents casting between arbitrary variables. Only casts between numeric variables and between sub and superclasses of the same object are allowed.
3) All numeric variables in Java are signed.

Answered by jaivir , an ibibo Master, at 7:21 PM on May 16, 2008

Hi Shard ,

A virtual machine (VM) is a software implementation of a machine (computer) that executes programs like a real machine.

A virtual machine was originally defined by Popek and Goldberg as an efficient, isolated duplicate of a real machine. Current use includes virtual machines which have no direct correspondence to any real hardware.[1]

Example: A program written in Java would receive services from the Java Runtime Environment software by issuing commands from which the expected result is returned by the Java software. By providing these services to the program, the Java software is acting as a "virtual machine," taking the place of the operating system or hardware for which the program would ordinarily have had to have been specifically written.

Answered by Reeta K , an ibibo Master, at 6:21 PM on May 16, 2008

A category of storing information/data that may or may not be interchangeable. An int is a data type, as is boolean. Each class is also considered its own data type.
In real life, "fruit" would be considered a data type, as would "number". Comparing a fruit to a number does not work, since they're not of the same data type. Unless you have a way to convert the fruit into a number, or the number into a fruit, they are incompatible.
In java, an "int" would be considered a data type, as would "boolean". Comparing an int to a boolean does not work - is 3 the same as true? The data types aren't compatible.

Answered by ayisha , an ibibo Master, at 5:39 PM on May 16, 2008

Well Sharad , In Java ,Names are used to refer to entities declared in a program. A declared entity is a package, class type, interface type, member (class, interface, field, or method) of a reference type, parameter (to a method, constructor, or exception handler), or local variable.

Names in programs are either simple, consisting of a single identifier, or qualified, consisting of a sequence of identifiers separated by "." tokens .

Every declaration that introduces a name has a scope (§6.3), which is the part of the program text within which the declared entity can be referred to by a simple name.

Packages and reference types (that is, class types, interface types, and array types) have members (§6.4). A member can be referred to using a qualified name N.x, where N is a simple or qualified name and x is an identifier. If N names a package, then x is a member of that package, which is either a class or interface type or a subpackage. If N names a reference type or a variable of a reference type, then x names a member of that type, which is either a class, an interface, a field, or a method.

For more details , Please visit the source site :

http://java.sun.com/docs/books /jls/second_edition/html/names.doc. html

Answered by Alok Gupta , an ibibo Guru, at 4:34 PM on May 16, 2008

well

A variable's data type determines the values it may contain, plus the operations that may be performed on it
The Java programming language supports eight primitive data types. A primitive type is predefined by the language and is named by a reserved keyword. Primitive values do not share state with other primitive values.

The eight primitive data types supported by the Java programming language are:

* 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).

* 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).

Java's primitive data types are very similar to those of C. They include boolean, byte, short, int, long, float, double, and char. The boolean type has been added. However the implementation of the data types has been substantially cleaned up in several ways.

1. Where C and C++ leave a number of issues to be machine and compiler dependent (for instance the size of an int) Java specifies everything.
2. Java prevents casting between arbitrary variables. Only casts between numeric variables and between sub and superclasses of the same object are allowed.
3. All numeric variables in Java are signed.

Answered by Om Prakash , an ibibo Master, at 3:13 PM on May 16, 2008

well Sharad, The Java programming language is strongly-typed, which means that all variables must first be declared before they can be used. This involves stating the variable's type and name, as you've already seen:

int gear = 1;

Doing so tells your program that a field named "gear" exists, holds numerical data, and has an initial value of "1". A variable's data type determines the values it may contain, plus the operations that may be performed on it. In addition to int, the Java programming language supports seven other primitive data types. A primitive type is predefined by the language and is named by a reserved keyword. Primitive values do not share state with other primitive values. The eight primitive data types supported by the Java programming language are:

Although Java is a language based on classes and all Java programs are built from classes, not all data types in Java are classes. In Java, there are two categories into which data types have been divided using this distinction:

| Primitives
|| Reference types

Primitives:

Primit ives are data types whose state represents a number, a character, or a true/false indication.

Primitive types are not class types; they do not provide any behavior associated with the type-appropriate values they hold. Java has eight primitive types that should look familiar to you from other languages:

1). boolean
2). byte
3). char
4). double
5). float
6). int
7). long
8). short

As you proceed through this chapter, each of these types is covered in detail. For now, take a look at

Reference Types:

Classes, interfaces, and arrays are known as reference types in Java. When you declare a variable of a reference type, you are specifying that the variable will refer, or point, to an object instead of holding a single value as in the case of a primitive.

This makes sense for classes because class instances are objects that have associated behavior and state that can be represented with many values as opposed to one. However, it might seem strange to you to see arrays in the same category. You'll get a closer look at the details a little later in this chapter, but arrays in Java are true objects whose elements can be either primitives or references to other objects.

For more information , please do visit source site:

http://www.informit.c om/articles/article.aspx?p=130 880
Hope it will help you out.

Answered by Uttam , an ibibo Master, at 2:01 PM on May 16, 2008