Primitive Data Types

Default values are for instance variables only.  If you define a local variable (inside a method), you
must assign a value to it yourself before using the variable in an expression.


Type       Bits    Default    Range (inclusive)

byte         8     0                    -128  to  127
char        16     0                       0  to  65,535   (unsigned)  
short       16     0                 -32,768  to  32,767
int         32     0          -2,147,483,648  to  2,147,483,647
float       32     0.0f       32 bit floating point number (decimals)
long        64     0L         -9,223,372,036,854,775,808  to  -9,223,372,036,854,775,807
double      64     0.0        64 bit floating point number (decimals)  
boolean      8     false      false or true


You can think of the bits as representing the size of the storage box.


Examples:




int a,b,c;
b = 13;
c = 5;
a = b + c;  // a would receive the value 18
a = b / c;  // a would receive the value 2 (decimal part truncated)
a = b % c;  // a would receive the value 3 (the remainder)

char someChar = 'A'; // same as someChar = 65;

int d = 26;
int e = 0x1a;  (0x indicates the number has been written in hexadecimal (base 16)
int f = 0b11010; (ob indicates the number has been written in binary)

double x = 323.4;
double y = 3.234e2;  // same as 323.4
float z = 3.14159f;  // must have the f, otherwise 3.14159 would be considered a double

Some General Assignment Rules (well not without a type cast or doing a manual conversion):
1) You can't store what's in a bigger storage box in a smaller storage box (the number of bits (size) matters).
   someChar = d;  would be illegal since someChar (16 bits) cannot hold the 32 bits used by variable d
   
2) You can't store a decimal number in a non decimal storage box.
   a = x;  would be illegal since a can only hold integer numbers.
   
3) You can't store a value that might be negative in an unsigned storage box.
   someChar = a;  would be illegal since a might hold a negative number and someChar is unsigned.



import java.util.Scanner;

public class Sample2 {
        
    public Sample2() {
    }
    
    public static void main(String[] args) {
        
        Scanner scan = new Scanner (System.in);
        
        System.out.println("Semester Grade");
        System.out.println();
        System.out.println();       

        System.out.print("Enter your semester 1 grade ");
        double s1 = scan.nextDouble();
        System.out.println();
        System.out.print("Enter your semester 2 grade ");
        double s2 = scan.nextDouble();
        System.out.println();
        System.out.print("Enter your final exam grade ");
        double exam = scan.nextDouble();
        System.out.println();
        System.out.println();
        double grade = (s1 + s2) / 2 * .8 + exam * .2;
        System.out.println("Your semester grade is " + grade );
        System.out.println();
        System.out.println();
        
    }
}
   
   

   
import java.util.Scanner;

public class Sample4 {
        
    public Sample4() {
    }
    
    public static void main(String[] args) {
        
        Scanner scan = new Scanner (System.in);
        
        System.out.println("Fahrenheit to Celsius");
        System.out.println();
        System.out.println();
        System.out.print("Enter the Fahrenheit Temperature ");
        double f = scan.nextDouble();
        double c = (5.0/9.0)*(f-32);
        System.out.println();
        System.out.println("The Celsius Temperature is " + c);
        System.out.println();
        System.out.println();


    }
}



import java.util.Scanner;

public class Sample3 {
        
    public Sample3() {
    }
    
    public static void main(String[] args) {
        
        Scanner scan = new Scanner (System.in);
        
        System.out.println("Slope of a Line");
        System.out.println();
        System.out.println();
        System.out.print("Enter x1 ");
        double x1 = scan.nextDouble();
        System.out.print("Enter y1 ");
        double y1 = scan.nextDouble();
        System.out.println();
        System.out.print("Enter x2 ");
        double x2 = scan.nextDouble();
        System.out.print("Enter y2 ");
        double y2 = scan.nextDouble();
        System.out.println();
        System.out.println();
        if (x2-x1==0)
        {
            System.out.println("The slope of the line is undefined");           
        }
        else
        {
            double slope = (y2-y1)/(x2-x1);
            System.out.println("The slope of the line is " + slope);
        }
        System.out.println();
        System.out.println();

    }
}


   
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