Oracle Certification Associate 1Z0-808
Links
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
- Java version
java -v
- 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.
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 |
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 Numbers
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); </source>