Java Course

Learn JAVA here!

Requirements:

eclipse.jpeg Eclipse IDE
java.pngJava Development Kit (JDK)
java.pngJava Runtime Envirentment (JRE)

1. Course

1. Basic syntaxes

public static void main(String[] args){
//Content of your code
}

Also, here are some few things that you need to know before starting using JAVA:

1.1 Comments

// This a comment

1.2 Multiligne comments

/* This is the start of a multiline comment
A comment here.
Another comment.
*/ This is the end of a multiline comment

1.3 Exemple:

public static void main(String[] args){
//A simple comment
/* This is the start of a multiline comment
A comment here.
Another comment.
*/ This is the end of a multiline comment
}
icons8-error-100.png Warning! After (almost) every sentence use a ; !

2 Variables and mathematic operators

2.1 Variables

Type Value
byte -128 to +127
short -32.768 to +32.767
int -2x10$^9$ to +2x10$^9$
long -9x10$^1$$^8$ to +9x10$^1$$^8$
float floating coma
char Unicode charchter between '' (e.g. 'A')
boolean true/false
String Text between "" (e.g. "Hi")

2.1.1 Variable syntaxes

Always follow this syntax: 1st. type of variable, 2nd. name of the variable, 3rd. value

Exemple:

int abc = 12;

String exemple:

String abc = "Hi";
icons8-error-100.png Warning! Always write String and not string!

2.1.2 Variable casting

To cast int to float:

int i = 123;
float f = (float)i;

To cast int to double:

int i = 123;
double d = (double)i;

To cast int to String:

int i = 123;
String s = new String();
s = s.ValueOf(i);

2.2 Math Operators

Opertator Description
+ Addition
- Subtraction
* Multiplication
/ Division

3. Print something (e.g. a text, a variable…)

Syntax:

int in1 = 10;
System.out.println(in1 + "is the value of in1")

4. Scanners

Syntax:

Scanner sc1 = new Scanner(System.in);

Import the Scanner class:

import java.util.scanner;

Import all the classes of the util package:

import java.util.*;

4.1 Get what the user typed

Syntax:

Scanner sc1 = new Scanner(System.in);
System.out.println("Please enter your age here:");
String st1 = sc.nextLine();
System.out.println("Your age is" + st1)

So the syntax for line 4 is: next<Variable type> (THIS DIDN'T WORKS WITH CHAR)
For char type:

System.out.println("Please type a character:");
Scanner sc1 = new Scanner(System.in);
String st1 = sc.nextLine();
char ch1 = st1.CharAt(0);
System.out.println("You typed" + ch1);
System.out.println("TERMINATED");

e.g. of using a scanner:

public static void main(String[] args) {
 
    Scanner sc1 = new Scanner(System.in);
    System.out.println("Please enter your age here:");
    int st1 = sc1.nextInt();
    System.out.println("Your age is: " + st1 + " years.");}
 
}

5. Conditions

5.1. if else

5.1.1 Operators

Operator Description
== test a tie
!= test an inequality
< strictly inferior
<= inferior or tie
> strictly superior
&& specify a condition(and)
|| specify a condition(or)

5.1. if else (back)

Syntax:

if (//condition)
{
    //if the condition is right do:
}
else
{
    //if the condition is false do:
}

e.g.:

int in1 = 10;
if (in1 < 0)
    System.out.println("The number is superior as 0!");
else
    System.out.println("The number is inferior as 0");

See also:

int in2 = 0;
if (in2 < 0)
System.out.println("in2 is negative.");
else if (in2 > 0)
System.out.println("in2 is positive.");
else
System.out.println("in2 is 0.");

So the result is gonna be :

JavaResult1.PNG

5.2. Multiple conditions

Syntax:

int in1 = 58;
if (in1 < 100 && in1 > 50)
System.out.println("in1's value is between 50 and 100.");
else
System.out.println("in1's value isn't between 50 and 100.");

So the result is gonna be:

JavaResult2.PNG

Comments

Add a New Comment
or Sign in as Wikidot user
(will not be published)
- +

Credits:

Creative Commons License