PIC20A Lecture 3 : Primitive data type

1. different primitive data types
2. how to declare primitive data types and assign values
3. how to perform operations on them.

• Data Types
• Variable Names
• Summary of Variables
• Operators
• Arithmetic Operators
• Relational and Conditional Operators

Identifier

• must start with a Unicode letter, underscore, or dollar sign ($)
• The other characters, if any, can be a Unicode letter, underscore, dollar sign, or digit.

• It can be used to represent international characters (Like Chinese characters or Russian characters).
• It is representated by , example \u1234 (\uXXXX, here XXXX are 2 hexadecimal numbers)

Primitve Data Types

Integer

int x = 27;
int y = 035,  z = 011; //  octal number  29  , 9
int w = 0x2a, u = 0X33; //  hexadecimal  42, 51

// compile this program by javac IntTest
// Run this program by java IntTest
/* output is 
x is 27
y is 29
z is 9
w is 42
u is 51
*/

public class IntTest {
    public static void main(String[] args) {
        int x = 27;
	int y = 035, z = 011; //  octal number  29 , 9
	int w = 0x2a, u = 0X33; //  hexadecimal  42, 51
	System.out.println("x is " + x);
	System.out.println("y is " + y);
	System.out.println("z is " + z);
	System.out.println("w is " + w);
	System.out.println("u is " + u);
    }
}

Float and Double

Long

Operators

Arithmetic Operators

The following table summarizes the binary arithmetic operations in the Java programming language.

Here's an example program, ArithmeticDemo, that defines two integers and two double-precision floating-point numbers and uses the five arithmetic operators to perform different arithmetic operations. This program also uses + to concatenate strings. The arithmetic operations are shown in bold:

public class ArithmeticDemo {
    public static void main(String[] args) {

        //a few numbers
        int i = 37;
        int j = 42;
        double x = 27.475;
        double y = 7.22;
        System.out.println("Variable values...");
        System.out.println("    i = " + i);
        System.out.println("    j = " + j);
        System.out.println("    x = " + x);
        System.out.println("    y = " + y);

        //adding numbers
        System.out.println("Adding...");
        System.out.println("    i + j = " + (i + j));
        System.out.println("    x + y = " + (x + y));

        //subtracting numbers
        System.out.println("Subtracting...");
        System.out.println("    i - j = " + (i - j));
        System.out.println("    x - y = " + (x - y));

        //multiplying numbers
        System.out.println("Multiplying...");
        System.out.println("    i * j = " + (i * j));
        System.out.println("    x * y = " + (x * y));

        //dividing numbers
        System.out.println("Dividing...");
        System.out.println("    i / j = " + (i / j));
        System.out.println("    x / y = " + (x / y));

        //computing the remainder resulting from dividing numbers
        System.out.println("Computing the remainder...");
        System.out.println("    i % j = " + (i % j));
        System.out.println("    x % y = " + (x % y));

        //mixing types
        System.out.println("Mixing types...");
        System.out.println("    j + y = " + (j + y));
        System.out.println("    i * x = " + (i * x));
    }
}

Variable values...
    i = 37
    j = 42
    x = 27.475
    y = 7.22
Adding...
    i + j = 79
    x + y = 34.695
Subtracting...
    i - j = -5
    x - y = 20.255
Multiplying...
    i * j = 1554
    x * y = 198.37
Dividing...
    i / j = 0
    x / y = 3.8054
Computing the remainder...
    i % j = 37
    x % y = 5.815
Mixing types...
    j + y = 49.22
    i * x = 1016.58

int a = 1;
a+=1;
a++;
a--;
++a;
--a;

Character

Example

char ch = 'C'; // a simple character
char lastName = '\u1A34'; (from '\u0000' to '\uFFFF') // unicode 

Boolean

boolean a = true;
boolean b = false;

Relational and Conditional Operators

public class RelationalDemo {
    public static void main(String[] args) {

        //a few numbers
        int i = 37;
        int j = 42;
        int k = 42;
        System.out.println("Variable values...");
        System.out.println("    i = " + i);
        System.out.println("    j = " + j);
        System.out.println("    k = " + k);

    //greater than
        System.out.println("Greater than...");
        System.out.println("    i > j = " + (i > j));     //false
        System.out.println("    j > i = " + (j > i));     //true
        System.out.println("    k > j = " + (k > j));     //false, they are equal

    //greater than or equal to
        System.out.println("Greater than or equal to...");
        System.out.println("    i >= j = " + (i >= j));   //false
        System.out.println("    j >= i = " + (j >= i));   //true
        System.out.println("    k >= j = " + (k >= j));   //true

    //less than
        System.out.println("Less than...");
        System.out.println("    i < j = " + (i < j));     //true
        System.out.println("    j < i = " + (j < i));     //false
        System.out.println("    k < j = " + (k < j));     //false

    //less than or equal to
        System.out.println("Less than or equal to...");
        System.out.println("    i <= j = " + (i <= j));   //true
        System.out.println("    j <= i = " + (j <= i));   //false
        System.out.println("    k <= j = " + (k <= j));   //true

    //equal to
        System.out.println("Equal to...");
        System.out.println("    i == j = " + (i == j));   //false
        System.out.println("    k == j = " + (k == j));   //true

    //not equal to
        System.out.println("Not equal to...");
        System.out.println("    i != j = " + (i != j));   //true
        System.out.println("    k != j = " + (k != j));   //false

    }
}

Variable values...
    i = 37
    j = 42
    k = 42
Greater than...
    i > j = false
    j > i = true
    k > j = false
Greater than or equal to...
    i >= j = false
    j >= i = true
    k >= j = true
Less than...
    i < j = true
    j < i = false
    k < j = false
Less than or equal to...
    i <= j = true
    j <= i = false
    k <= j = true
Equal to...
    i == j = false
    k == j = true
Not equal to...
    i != j = true
    k != j = false