chapter 1- variables and datatypes
Just like we have some rules that we follow to speak English(grammar), we have some rules to follow while writing a java program. The set of these rules is called syntax(vocabulary and grammar of java).
Variables
The variable is a container that stores a value. This value can be changed during the execution of the program.
Example: int number = 8;
here, int is a data type, the number is the variable name and 8 is the value it stores
Rules for declaring a variable name
we can choose a name by declaring a java variable
if the following rules are followed:
1. Must not begin with a number ==>int 1arry; is invalid!
2. Name is case sensitive ==>dhruv and Dhruv are different!
3. Should not be a keyword( like void).
4. white space is not allowed. ==>int developer dhruv is invalid.
5. Can contain alphabets, $ character _ character, and digits if the other conditions are met.
Data types
Data types in java fall under the following categories.
1.Primitive data types (intrinsic)
2.Non-primitive data types(derived)
Primitive Data Types
Java is statically typed.==.variables must be declared before use!
there are 8 types of primitive data types supported by java:
1.BYTE - valve ranges from -128 to 127
takes 1 byte
default value is zero
2.SHORT - value ranges from-(2^16) to (2^16)-1
takes 2 bytes
default value is 0
3.INT - value ranges from-(2^32) to (2^32)-1
takes 4 bytes
default value is 0
4.FLOAT - value ranges from (see docs)
takes 4 bytes
default value is 0.0f
5.LONG - value ranges from -(2^64) to (2^64)-1
takes 8 bytes
default value is 0
6.DOUBLE - value ranges from (see docs)
takes 8 bytes
default value is 0.0d
7.CHAR - value ranges from 0 to 65535(2^16-1)
takes 2 bytes ==>because it supports Unicode
default value is '100000'
8.BOOLEAN-value can be true or false
size depends on JVM
default value is false
QUICK QUIZ: write a java program to add 3 numbers.
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