Changes

Java (view source)

Revision as of 10:53, 12 April 2022

207 bytes added , 10:53, 12 April 2022

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→‎Numeric variables

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All the code can be found at: [https://github.com/rafahsolis/javaTutorial javaTutorial]

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== Install ==

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==Install==

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=== With apt ===

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===With apt===

<nowiki>sudo apt-add-repository ppa:webupd8team/java

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sudo apt-get update

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sudo apt-get update

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sudo apt-get install oracle-java8-installer</nowiki>

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sudo apt-get install oracle-java8-installer</nowiki>

Also ensure your JAVA_HOME variable has been set to:

/usr/lib/jvm/java-8-oracle

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=== From Source ===

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===From Source===

wget --header "Cookie: oraclelicense=accept-securebackup-cookie" http://download.oracle.com/otn-pub/java/jdk/8u5-b13/jdk-8u5-linux-x64.tar.gz

sudo update-alternatives --install /usr/bin/java java /usr/lib/jvm/oracle_jdk8/jre/bin/java 2000

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update-alternatives --display javac

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== hello world ==

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==hello world==

public class aplication {

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}</source>

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== Numeric variables ==

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==Numeric variables==

public class variables {

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}</source>

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== Strings ==

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== Data types ==

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byte b; byte (8 bits)

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short s; short (16 bits)

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int i; Integer (32 bits)

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long lo; long (64 bits)

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float f=4.0f; (32 bits) Not precise use big decimal instead

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double d; (64 bits) Not precise use big decimal instead

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char c; (16 bits)

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String st; String

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boolean isTrue; true/false

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Todo: Arrays etc...

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==Strings==

public class stringstuto {

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}

}</source>

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== Enum type ==

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==Enum type==

See code example:

[https://github.com/rafahsolis/javaTutorial/blob/master/EnumTypes.java EnumTypes.java]

[https://github.com/rafahsolis/javaTutorial/blob/master/Animal.java Animal.java]

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== Operators ==

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==Operators==

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=== Asignment ===

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===Asignment===

= Asignment

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=== Arithmetic ===

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===Arithmetic===

+ Additive

- Substraction

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% Remainder

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=== Increment / Decrement ===

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===Increment / Decrement===

++ Increment

-- Decrement

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=== Logic ===

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===Logic===

== Equal to (*)

!= Not Equal to

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(*) Check .equals()

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=== Bitwise and Bit Shift Operators ===

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===Bitwise and Bit Shift Operators===

~ Unary bitwise complement

<< Signed left shift

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^ Bitwise exclusive OR

| Bitwise inclusive OR

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=== Type comparison operator ===

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===Type comparison operator===

instanceof

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== Loops ==

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==Loops==

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=== While ===

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===While===

int myInt = 0;

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}</source>

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=== For ===

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===For===

for(int i=0; i<5;i++){

System.out.printf("The value of i is %d\n", i);

}</source>

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=== Do While ===

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===Do While===

public static void main(String[] args) {

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}</source>

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== Conditional ==

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==Conditional==

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=== if ===

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===if===

int value = 20;

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}</source>

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=== switch case ===

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===switch case===

switch(VariableIntOrString){

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}</source>

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== User Input ==

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==User Input==

import java.util.Scanner;

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*Note: Ctrl + Shift + O in eclipse adds all the imports you need.

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== Arrays ==

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==Arrays==

int[] values;

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values.length; → returns the array lenght

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=== Iterating trough an array ===

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===Iterating trough an array===

String[] fruits = {"apple", "banana", "pear", "kiwi"};

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}

</source>

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=== Multidimensional arrays ===

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===Multidimensional arrays===

int[][] grid = {

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</source>

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== Classes and Objects ==

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==Classes and Objects==

class Person {

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}

</source>

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== Setters and 'this' ==

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==Setters and 'this'==

package tutorial1;

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}

</source>

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== Constructors ==

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==Constructors==

Methods that are executed at the instantiation of a class.

There can be more than one, diferentiated on the number of parameters that are passed at the instantiation of a class.

[https://github.com/rafahsolis/javaTutorial/blob/master/constructors.java example code]

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== static ==

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==static==

static is used to define class variables and methods.

static objects are referenced by the class, not the instance.

[https://github.com/rafahsolis/javaTutorial/blob/master/staticMethod.java example code]

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== final ==

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==final==

final is used to declare constants. The asignment of value must be at the declaration

[https://github.com/rafahsolis/javaTutorial/blob/master/constructors.java example code]

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== StringBuilder / formatting ==

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==StringBuilder / formatting==

StringBuilder is more efficient for strings appending than using +=

[https://github.com/rafahsolis/javaTutorial/blob/master/StringBuilderBufferFormatting.java example code]

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== Inheritance ==

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==Inheritance==

Use key word extends at the class declaration

private variables and methods are not inherited.

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[https://github.com/rafahsolis/javaTutorial/blob/master/Car.java Car.java]

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== Packages ==

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==Packages==

Packages allow to have classes with the same name as long as they are in diferent packages.

In orther to be able to use the classes from a package it must be imported.

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[https://github.com/rafahsolis/javaTutorial/blob/master/packageexample.java packageexample.java]

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== Interfaces ==

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==Interfaces==

If you whant to define a method for more than one class, you should use an interface (rigt click on project > new > interface)

Interfaces file names should start with upper case.

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[https://github.com/rafahsolis/javaTutorial/blob/master/Info.java Info.java]

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== public/private/protected variables ==

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==public/private/protected variables==

public → can be accesed from anywhere.

public final static → constant.

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no access specifier → only accesible from the same package.

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== Polymorphism ==

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==Polymorphism==

You can point a variable of a parent type to a child type, it will have the methods from it's type but overriden by the subclass.

You wont be able to call methods from the subclass that are not implemented on the variable type.

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[https://github.com/rafahsolis/javaTutorial/blob/master/Tree.java Tree.java]

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== Encapsulation and the API ==

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==Encapsulation and the API==

Variables whithin a class should be private and if you need to change them use getters and setters.

[https://docs.oracle.com/javase/8/docs/api/ Java 8 API]

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== Casting Numerical Values ==

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==Casting Numerical Values==

See [https://github.com/rafahsolis/javaTutorial/blob/master/Casting.java examples]

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== Upcasting and Downcasting ==

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==Upcasting and Downcasting==

Code examples:

[https://github.com/rafahsolis/javaTutorial/blob/master/UpcastingDowncasting.java UpcastingDowncasting.java]

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[https://github.com/rafahsolis/javaTutorial/blob/master/Machine.java Machine.java]

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== Generic class ==

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==Generic class==

Can work with other objects specified at the class instantiation.

[https://github.com/rafahsolis/javaTutorial/blob/master/Generic.java Generic.java]

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}

</source>

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=== Generics and Wildcards ===

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===Generics and Wildcards===

See: [https://github.com/rafahsolis/javaTutorial/blob/master/Generic.java Generic.java]

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== Files ==

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==Files==

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=== Reading text files ===

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===Reading text files===

See: [https://github.com/rafahsolis/javaTutorial/blob/master/ReadTextFile.java ReadTextFile.java]

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=== Reading files (Try-With-Resources) ===

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===Reading files (Try-With-Resources)===

This requires at least Java 7

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}

}</source>

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=== Reading files with FileReader ===

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===Reading files with FileReader===

import java.io.BufferedReader;

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}</source>

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=== Writing files ===

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===Writing files===

import java.io.BufferedWriter;

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}</source>

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== Anonymous class ==

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==Anonymous class==

see: [https://github.com/rafahsolis/javaTutorial/blob/master/AnonymousClass.java AnonymousClass.java]

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== Exceptions ==

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==Exceptions==

[http://docs.oracle.com/javase/8/docs/api/java/lang/Exception.html Class Exception]

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=== trows ===

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===trows===

package tutorialJava;

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}</source>

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=== try/catch ===

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===try/catch===

import java.io.IOException;

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}

}</source>

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=== Runtime exceptions ===

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===Runtime exceptions===

The compiler does not force you to handle them.

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}</source>

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== Abstract Class ==

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==Abstract Class==

Classes that can't be instantiated, only inherited.

See example files:

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[https://github.com/rafahsolis/javaTutorial/blob/master/AbstractClassChild1.java AbstractClassChild1.java]

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== .equals() Method ==

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==.equals() Method==

It's used to compare if two objects of the same class are equal. In order to be able to use it you must override this method by:

Right click on the class > source > Generate hashCode() and Equals()...

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[https://github.com/rafahsolis/javaTutorial/blob/master/Persona.java Persona.java]

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== Inner Classes ==

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==Inner Classes==

Clases declared inside other classes.

Code examples:

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[https://github.com/rafahsolis/javaTutorial/blob/master/Robot.java Robot.java]

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== Recursion ==

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==Recursion==

See code example:

[https://github.com/rafahsolis/javaTutorial/blob/master/Recursion.java Recursion.java]

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== Serialization ==

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==Serialization==

Turning an object into binary data, deserialization is the opposite.

Code examples:

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[https://github.com/rafahsolis/javaTutorial/blob/master/Persona.java Persona.java]

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=== Multiple Objects ===

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===Multiple Objects===

[https://github.com/rafahsolis/javaTutorial/blob/master/WriteMultipleObjects.java WriteMultipleObjects.java]

[https://github.com/rafahsolis/javaTutorial/blob/master/ReadMultipleObjects.java ReadMultipleObjects.java]

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=== Transient Keyword ===

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===Transient Keyword===

To prevent the serialization of some variable in a class you can declare it as:

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Static fields aren't serialized too.

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== Eclipse shortcuts ==

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==Eclipse shortcuts==

Ctrl + Space → Autocomplete.

Ctrl + d → Delete Line

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Ctrl + m → Toogle fulscreen

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== Notes ==

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==Notes==

Hibernate → Java ORM framework for web design

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Changes

Java (view source)

Revision as of 10:53, 12 April 2022

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