Java lesson

[Blaine]

Java lessons 1 -"hello World"

Source -

public class Hello
{
public static void main (string[] args)
{
System.out.println("Hello world");
}
}

"public class" delcares program name and is followed by {} any code within those brackets defines hello class.

public static void main ( string[] args) Statard code to define the starting point of nearly all java programs. Contains the method named "main" That will contain the actual programming instructions with the brackets.

public static void willl be defined in a later lesson same with ( string[] args)

System.out.println( " hello world"); ( !statements preforming a task must end with a simicolon)

System.out.pritln just prints whatever is in the (" ").

[Blaine]

Java lesson 2 - "First Variable"

Source -
public class Firstvar
{
public static viod main(string[] args)
{
String str = "Variable One";
System.out.println(str);
str = "variable Two";
System.out.println(str);
}
}

variable syntax "datatype Variablename = value;"

Here are some Variable data types

char- A single character
string- a string of characters
int - any integer from -2.14 billion to 2.14 billion
float- number with a decimal point
boolean- true or false

[Blaine]

Lesson 3- "Arithmetical operators"

+ : addition ( and Combining strings)
- : subtraction
* : multiplication
/ : Division
% : modulus
++: Increment
-- : Decrement

Source:
public class artimetic
{
public static void main (string[] args)
{
int add = 40 + 10;
String addstr = " Java is" + " great";
float sub = 35.75f - 28.25f;
int mul = 7 * 5;
int mod = 65 % 2;
int incr = 5 ; incr = ++incr
int decr = 5 ; decr = --decr;

System.out.println("Numbers add total " +add);
System.out.println(" Strings Combined " +addstr);
System.out.println(" Subtraction result is: " +sub);
System.out.println("Multiplaction Result: " +mul);
System.out.println("modulus Result: " + mod);
System.out.println(" Increament Result: " +incr);
System.out.println(" Decrement Result: " + decr);
}
}


The output Panel should show
Numbers add total 50
Strings combined Java is Great
Subtraction result: 7.5
Multiplaction result: 35
Modulus Result : 1
Increment Result: 6
Decrement Result: 4

[Blaine]

Java lesson 4 - " Assignment Operators"

Operator Example Equivalent
(=) (a = b) (a = b)
(+=) (a +=b) (a = a +b)
(-=) (a -= b) (a = a - b)
(*=) (a *= b) (a = a * b)
(/=) (a /= b) (a = a / b)
(%=) (a %= b) (a = a & b)

Source:

public class assignment
{
public class static void main (string[] args)
{
String a = "Java", b= " Rules"; a += b
System.out.println(" Combined Strings: " + a);

int c = 10, d = 10; c += d;
System.out.println(" Adding two numbers: " +c );

float e = 7.5f, f = 2.25f; e -=f;
System.out.println(" Subtracting floats: " + e);

int g = 8, h = 2; g *= h;
System.out.println (" Multiplying Integers: " +g);

int i = 8, j = 4; i /= j;
System.out.println(" Dividing Integers: " +i );

int k = 8, l = 4; K %= l;
System.out.println(" Modulus Result " + k);
}
}

The Output of this will be:


Combined strings: java rules
adding two numbers: 20
Subtracting floats: 5.25
Multiplying Integers: 16
Dividing Integers: 2
Modulus Result: 0

[Blaine]

Lesson 5 " logical operators"

&& - Logical AND
|| - Logical OR
! - Logical NOT

Source-

Public class logical
{
public static void main (String[] args)
{
boolean a = true, b = false;

boolean c1 = ( a && a); // sees if both are true
boolean c2 = ( a && b);
boolean c3 = (b && b);

boolean c4 = (a || a); // sees if either is true
boolean c5 = (a || b);
boolean c6 = (b || b);

boolean c7 = !a;
boolean c8 = !b;

System.out.println(" And: \n1: "+c1+" 2: "+c2+" 3: "+c3);
System.out.println(" OR: \n4: "+c4+" 5: "+c5+" 6: "+c6);
System.out.println(" NOT: \n7: "+c7+" 8: " +c8);
}
}

output
AND:
1: true 2: false 3: false
OR:
4: true 5: true 6: false
NOT:
7:false 8:true

[Blaine]

Lesson 6 - "Comparison Operators"

== - Equality
!= - Inequality
> - greater than
< - less than
>= - greater than or equal to
<= - less than or equal to

source-

public class camparison
{
public static void main (String[] args)
{
boolean testsrt ("java" == "monkey");
System.out.println(test stings: " + teststr);

boolean testnum = ( 1.785 == 1. 785);
System.out.println("test numbers: " + testnum);

boolean testbool = ( true != true);
System.out.println("Test booleans: " + testbool);

boolean testless = ( 2 < 200);
System.out.println(" Test less than: " + testless);

boolean lesseq = (2 <= 200) ;
System.out.println("test less or equal: " + lesseq);

boolean testgtr = ( -1 > 1);
System.out.println("test greater than: " + testgtr);
}
}

output window
test strings: false
test numbers: true
test booleans: false
test less than: true
test less or equal: true
test greater than: false