More About primitive types

1. sizes Of primitive data types

Data Type	Size (in bytes)
byte	1
short	2
int	4
long	8
float	4
double	8
char	2

boolean: The boolean data type has only two possible values: true and false. This data type represents one bit of information, but its "size" isn't something that's precisely defined.

2. If you are using primitive data types as local variables, then you must initialize the variable before using. Other wise compiler will throw error.

Example

class PrimitiveDeclaration{
 public static void main(String args[]){
  int var1;
  System.out.println(var1);
 }
}

When you tries to compile the above program below error thrown

PrimitiveDeclaration.java:5: error: variable var1 might not have been initialized
 System.out.println(var1);
 ^
1 error

3. Assigning data to compatibility types

Java permits to assign a value of one data type to the value of other if types are compatible. I.e, we can assign a data of float to double, byte to int, char to int etc.,

When you assign a character variable to int variable, then int variables store the Uni code of the variable.

Example

class Compatible{
 public static void main(String args[]){
  char charVar = 'a';
  int intCharVar = charVar;
  byte byteVar = 100;
  short shortVar = byteVar;
  int intVar = shortVar;
  long longVar = intVar;
  float floatVar = longVar;
  double doubleVar = floatVar;
  
  System.out.println(charVar);
  System.out.println(intCharVar);
  System.out.println(byteVar);
  System.out.println(shortVar);
  System.out.println(intVar);
  System.out.println(longVar);
  System.out.println(floatVar);
  System.out.println(doubleVar);
 }
}

Output

a
97
100
100
100
100
100.0
100.0

4. If you are trying to assign data of one type to the other incompatible type compiler will throw error.

Example

class Compatible{
 public static void main(String args[]){
  int intVar = 10;
  boolean a = intVar;
 }
}

While compiling you will get the below error

Compatible.java:6: error: incompatible types
 boolean a = floatVar;
 ^
 required: boolean
 found: float
1 error

5. If you want to assign a higher data type value to compatible lower data type, then you should externally cast it, otherwise compiler will throw an error by saying “possible loss of precision”.

Syntax:  

   dataType value1 = (dataType) value2;

class Compatible{
 public static void main(String args[]){
  double doubleVar = 109.05;
  char ch = doubleVar;
  
  System.out.println(doubleVar);
  System.out.println(ch);
 }
}

while compiling you will get the below error.

Compatible.java:5: error: possible loss of precision
 char ch = doubleVar;
 ^
 required: char 
 found: double
1 error

To solve the above error, we need to cast explicitly like below

class Compatible{ 
 public static void main(String args[]){
  double doubleVar = 109.05;
  char ch = (char)doubleVar;
  
  System.out.println(doubleVar);
  System.out.println(ch);
 } 
}

6. Always assign a value to a float variable by appending “f” to it like below

float floatVar = 10.09f

other wise compiler will throw error.

class Compatible{
 public static void main(String args[]){
  float floatVar = 10.09;
  System.out.println(floatVar);
 }
}

While compiling you will get the below error

Compatible.java:3: error: possible loss of precision
 float floatVar = 10.09;
 ^
 required: float
 found: double
1 error

To solve the above error define the float variable like below

    float floatVar = 10.09f;

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