variables in java

The Java programming language defines the following kinds of variables:

Instance Variables (Non-Static Fields) Technically speaking, objects store their individual state in "non-static fields," that is, fields declared without the static keyword. Non-static fields are also known as instance variables because their values are unique to each instance of a class (to each object, in other words);

Class Variables (Static Fields) A class variable is any field declared with the static modifier; this tells the compiler that there is exactly one copy of this variable in existence, regardless of how many times the class has been instantiated.

Local Variables Similar to how an object stores its state in fields, a method will often store its temporary state in local variables . As such, local variables are only visible to the methods in which they are declared; they are not accessible from the rest of the class.

Parameters The important thing to remember is that parameters are always classified as "variables," not "fields."

 

Primitive Data Types

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).

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).

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).

float The float data type is a single-precision 32-bit IEEE 754 floating point.

double The double data type is a double-precision 64-bit IEEE 754 floating point.

boolean The boolean data type has only two possible values: true and false .

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). 

 

Arrays

An array is a container object that holds a fixed number of values of a single type. The length of an array is established when the array is created. After creation, its length is fixed.

One way to create an array is with the new operator.

Alternatively, you can use the shortcut syntax to create and initialize an array

 

 

 

 

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