Oracle Certification Associate 1Z0-808

Installation

Windows

<source lang="Shell"> C:\Program Files\Java </source>

• Java Se Development Kit 8
  • Java FX SDK
  • Private JRE - Java Runtime Edition
  • Java Mission Control Tools

Can also be installed:

• • Development Tools
  • Source Code
  • Public JRE

Linux

<source lang="Shell"> sudo apt-get install oracle-java8-installer cd /usr/lib/jvm/java-8-oracle

1. Java version

java -v

1. Java Compiler

javac -version </source>

Basics

Main Method

<source lang="Java"> public static void main(String[] args]) </source>

Comments

<source lang="Java"> // Single Line Comment

/* Multi Line Comment

• /

/**

* Java Doc Comment
* @param
* @return 
*/

</source>

Import Conflicts

<source lang="Java"> import java.util.*; import java.sql.*;

// ==> in code = COMPILATION error Date date; </source>

Static Imports

It is not a good idea to do static imports a lot in a projet because it makes difficult to understand where the methods / constants come from

• Static imports are for importing static members
• Classic imports are for importing classes

it can be used for methods and constants for example <source lang="Java"> import static java.lang,Math.*;

// Instead of typing Math.min(1,2); we can just type min(1,2) // Because of the static import </source>

Primitives

It is not a good practice to use "l" instead of "L" while declaring long numbers because "l" looks like a "1" number so it can be confusing

Since Java 7 we can use "_" to makes number easier to read.

• Can be anywhere except: beginning of literal, end of literal and right before or right after the decimal point.
• Error: Illegal Underscore ==> the code does not compile

KeyWord	Size	Examples	Smallest Data-Type
Boolean	-	true
Numbers without decimal points
byte	8-bits	1
short	16-bits	12	comment
int	32-bits	100	Default all numbers in Java
long	64 bits	12	Requires "L" letter to avoid compilation error, even when stored in long variable
float	32-bits	123.45	Requires letter "f" following the numbers
double	64-bits	123.45	Default all primitives or all that similar types. Can use "d" / "D" letter to specify Can convert a Float to Double
char	16-bits	'a'

Octal Numbers

Octal Numbers are numbers from 0 to 7. They can be used in java as

<source lang="Java"> // Valid int octalNumber = 07;

// Invalid - Number is too large, Compilation Error ! int octalNumber = 08; // it is not an octal number

// Valid - BUT coding standards prohibit use of octal literals, as they may be easily confused with decimal literals int octalNumber = 010 // 8 in decimal;

// Valid int declaration int octalNumber = 022; // 18 in decimal

// Valid int declaration int octalNumber = 8;

System.out.println(octalNumber); // print it's int value // Integer to octal String Integer.toOctalString();

</source>

Hexadecimal

Hexadecimals are numbers from 0 to 9 and letters from A to F <source lang="Java"> // Valid int firstHexNumber = 0xF; // 15 in decimal int secondHexNumber = 0x1E; // 30 in decimal

// Print the decimal value System.out.println(firstHexNumber); // print the Hexadecimal value: Integer.toHexString(firstHexNumber);

// p indicates hexadecimal floating point number double hexPi = 0x1.91eb851eb851fp1 </source>

Binary

<source lang="Java"> // Valid int firstBinary = 0xF; // 15 in decimal int secondBinary= 0x1E; // 30 in decimal

// Print the decimal value System.out.println(firstBinary ); // print the Hexadecimal value: Integer.toBinaryString(firstHexNumber); </source>

Scientific Notation

<source lang="Java"> // Both are valid and compile double scientificNotation = 5.000125E3 // in double 5000.125 double scientificNotation = 5.000125E03 // in double 5000.125 </source>

Chars

<source lang="Java"> char ch = 'a'; char ch1 = '1'; // it is still a char char uniChar = '\u03A9'; // upper case greek omega character char romanNumber= '\u0216C'; // roman 50 number </source>