reading-notes

Class-01 reading Summary

The Java programming language defines the following kinds of variables:

1. Instance Variables
2. Class Variables
3. Local Variables
4. Parameters

Primitive Data Types:

byte:

• 8-bit
• signed two’s complement integer
• has a minimum value of -128 and a maximum value of 127
• useful for saving memory in large arrays
• They can also be used in place of int where their limits help to clarify your code

short:

• 16-bit
• signed two’s complement integer
• Has a minimum value of -32,768 and a maximum value of 32,767
• you can use a short to save memory in large arrays

int:

• 32-bit
• signed two’s complement integer
• has a minimum value of -231 and a maximum value of 231-1
• Use the Integer class to use int data type as an unsigned integer

long:

• 64-bit
• two’s complement integer.
• has a minimum value of -263 and a maximum value of 263-1
• Use this data type when you need a range of values wider than those provided by int

float:

• single-precision
• 32-bit IEEE 754 floating point
• use a float (instead of double) if you need to save memory in large arrays of floating point numbers
• should never be used for precise values, such as currency

double:

• a double-precision
• 64-bit IEEE 754 floating point
• should never be used for precise values, such as currency.

boolean:

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

char:

• single-precision
• 16-bit Unicode character
• It has a minimum value of ‘\u0000’ (or 0) and a maximum value of ‘\uffff’ (or 65,535 inclusive).

### Arrays:

Arrays need to be declared and then created. In order to declare a variable that will hold an array of integers, we use the following syntax:

int[] arr;

and to create array with for example a size = 5:

arr = new int[5];