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README.md

Java---My-learning-notes

learning java :-)

python VS java

https://www.rose-hulman.edu/class/cs/csse220/200830/web/Resources/Python_vs_Java.html

java, get set methods

https://stackoverflow.com/questions/36102768/java-get-set-methods

  • To understand get and set, it's all related to how variables are passed between different classes.
  • The get method is used to obtain or retrieve a particular variable value from a class.
  • A set value is used to store the variables.
  • The whole point of the get and set is to retrieve and store the data values accordingly. Ex:
//here

java packages

https://beginnersbook.com/2013/03/packages-in-java/

package myPackage;

import outsidePackage.someClass;

private static vs public static and final

https://developer.salesforce.com/forums/?id=906F0000000AuyOIAS

  • static : Static methods (and variables) can be used without instantiating a new instance of the class
  • non-static : Non-static method (and variables) must have a new instance of the class instantiated in order to be used. Typically these rely on data inside the class that then is refered to inside the class

https://beginnersbook.com/2014/07/final-keyword-java-final-variable-method-class/

  • final variables are nothing but constants.
  • A final method cannot be overridden.
  • We cannot extend a final class.

Annotations

https://beginnersbook.com/2014/09/java-annotations/

  • Java Annotations allow us to add metadata information into our source code, although they are not a part of the program itself.
  • An annotation always starts with the symbol @ followed by the annotation name. The symbol @ indicates to the compiler that this is an annotation.

Constructor overloading

Interfaces

  • Ex. public interface Abc { return-type method-name1(parameter-list); }
  • An interface is a contract (or a protocol, or a common understanding) of what the classes can do.
  • One of the main usage of interface is provide a communication contract between two objects.
  • main use of interface is to facilitate polymorphism.
  • python does not have any equivalent of interfaces, The closest thing is probably the abstract base classes module, which allows you to define common methods for a set of classes.
  • Ex.

class Abstract: def myFunc(self): raise NotImplementedError("The method not implemented")

junit

http://www.vogella.com/tutorials/JUnit/article.html#junit_intro

  • Unit test : A unit test is a piece of code written by a developer that executes a specific functionality in the code to be tested and asserts a certain behavior or state.
  • Integration / functional test : An integration test aims to test the behavior of a component or the integration between a set of components. Integration tests check that the whole system works as intended, therefore they are reducing the need for intensive manual tests.
  • src/test/java - for test classes
  • A JUnit test is a method contained in a class which is only used for testing. This is called a Test class. To define that a certain method is a test method, annotate it with the @Test annotation.
  • You use an assert method, provided by JUnit or another assert framework, to check an expected result versus the actual result.
  • These method calls are typically called asserts or assert statements.

gradle

https://www.stubbornjava.com/posts/multi-project-builds-with-gradle-and-fat-jars-with-shadow https://docs.gradle.org/current/userguide/command_line_interface.html

  • gradle/ The gradle/ directory is the default location for including gradle scripts.

  • build.gradle The build.gradle file is where we will load all plugins This is also where we handle building our fat JAR using the Shadow JAR plugin

  • ./gradlew clean

Uses your project's gradle wrapper to execute your project's clean task. Usually, this just means the deletion of the build directory.

uberJar, fatJar and shadowJar in Gradle?

There is no difference whatsoever. These terms are all synonyms of each other.

The term "uber-jar" may be more commonly used in documentations (take the maven-shade-plugin documentation for example) but "fat-jar" is also widely used.