class A {  

    int data = 50; // instance variable  

    static int m = 100; // static variable  

    void method () {  

        int n = 90; // local variable  

    }  

} //end of class

Data Types in Java

boolean

char

byte

short

int

long

float

double

Data-Type  Default-Value  Default-size

boolean    false          1 bit

char       '\u0000'       2 byte

byte       0              1 byte

short      0              2 byte

int        0              4 byte

long       0L             8 byte

float      0.0f           4 byte

double     0.0d           8 byte

class Simple {  

    public static void main (String[] args) {  

        int a = 10;  

        int b = 10;  

        int c =  a + b;  

        System.out.println(c);  

    }

}

--------------------------------------------

Output: 
20

class Simple {  

    public static void main (String[] args) {  

        int a = 10;  

        float f = a;  

        System.out.println(a);  

        System.out.println(f);  

    }

}

--------------------------------------------

Output:

10

10.0

- From a byte to a short, an int, a long, a float, or a double

- From a short to an int, a long, a float, or a double

- From a char to an int, a long, a float, or a double

- From an int to a long, a float, or a double

- From a long to a float or a double

- From a float to a double

class Simple {  

    public static void main(String[] args) {  

        float f = 10.5f;  

        //int a = f; // Compile time error  

        int a = (int) f;  

        System.out.println(f);  

        System.out.println(a);  

    }

}

--------------------------------------------

Output:

10.5

10

- From a byte to a char

- From a short to a byte or a char

- From a char to a byte or a short

- From an int to a byte, a short, or a char

- From a long to a byte, a short, a char, or an int

- From a float to a byte, a short, a char, an int, or a long

- From a double to a byte, a short, a char, an int, a long, or a float

class Simple {  

    public static void main(String[] args) {  

        // Overflow  

        int a = 130;  

        byte b = (byte) a;  

        System.out.println(a);  

        System.out.println(b);  

    }

}

--------------------------------------------

Output:

130

-126

class Simple {  

    public static void main (String[] args) {  

        byte a = 10;  

        byte b = 10;  

        // byte c = a + b; 

        // Compile Time Error: because a + b = 20 will be int  

        byte c = (byte) (a + b);  

    System.out.println(c);  

    }

}

--------------------------------------------

Output:

20

Operators in java

Java Unary Operator Example: ++ and --

class OperatorExample {  

    public static void main (String args[]) {  

        int x = 10;  

        System.out.println(x++);//10 (11)  

        System.out.println(++x);//12  

        System.out.println(x--);//12 (11)  

        System.out.println(--x);//10  

    }

}

--------------------------------------------

Output:

10

12

12

10

(x++)

(--x)