Java nedir?

 Compilation — source kodun mashinin basha dusheceyi dile cevrilmesidir. It is the process the computer takes to convert a high-level programming language into a machine language that the computer can understand.

Source code — — ->compiling — —->Binary code (0 ; 1)

Compiler — programi tam cevirir sonra icra edir. Compiler xetalari cevirenden sonra deyir.

Interpreter — programi setir setir oxuyur ve icra edir. Interpreter xetalari ilk sehv tapildiqda deyirl.

Compiled languages : C, C++, Go, Fortran, Pascal.

Language → (Compiling) → Machine code → Ready to Run!

Interpreted languages: Python, PHP, Ruby, JavaScript.

Language → Ready to Run! → (Interpreting) → Virtual Machine → Machine code.

  • Java hem compiler hem de interpreter dildir.

MyProgram.java → (Compiler) → MyProgram.class → (JVM) → MyProgram(01000110101010)

Java Compile-time platfomadan asili deyil, Bytecode platformadan asili deyil lakin JVM-den asilidir, Run-time da ise platformadan asilidir.

JDK((JRE(JVM))).

JDK — Java Development Kit, icinde JRE — Java Runtime Environment var, JRE nin icinde JVM — Java Virtual Machine var.

JVM in icinde Class Loader, Bytecode verifier ve Interpreter var.

JRE — .class faylaarini yeni byte kodlari binary kodlara cevirmek ucundur.

Java source kodu byte koda cevirmek ucun compile etmek lazimdir cmd-de javac faylin adi ve extension-u. Mes: javac Selam.java. Bundan sonra Selam.class fayli yaranir, burda binary kodlar olur. Novbeti addim ise kodu run etmekdir. Bunun ucun machine code generate etmek larimdir.

java Selam yazim run ede bilerik veya java -classpath . Main


Eger byte kodlara baxmaq isteyirikse javap -c Selam.class yazmaq bes edir.

  • Bir java source kodda yalniz ve yalniz bir eded publik class olur, lakin istenilen qeder public olmayan klass ola biler.

// MyNameIsParvin — pascal naming convention

//myNameIsParvin — camel naming convention

Her bir statement mutleq noqte vergulle (;) bitmelidir, lakin block noqte vergulle bitmir.

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Lesson1: JDK, JVM, JRE

Изображение
1. Compiler - takes the entire programming code written in high language and translates the whole of it into machine code at once. After this process the an executable file will be ready to run. The translation takes some times to be done, but after that execution is so fast. 2. Interpreter - takes each single instructions of the code translates it and then executes it on its own. The translation step is before the program runs is fast, but execution is slow. JDK = JRE + development tools JRE = JVM + library class JDK -> Java Development Kit. A kit which provides the environment to develop and execute (run) Java program. JRE -> Java Runtime Environment. Provides environment to only run. JVM -> Java Virtual Machine f * Compiled: Fortran, C, C++, Pascal, Haskell, Rust, Go * Interpreted: JavaScript, PHP, Python, Ruby Java both compiled and interpreted language. Terminalda : javac Main.java yazdiqda, source fayli(.java) bytecode(.class) faylina cevirir. Terminalda: java Main (bu z
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SE_21_Lesson_11: Inheritance, Polymorphism

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Изображение
-> static block: package org.example.test3 ; public class Blocks { static { System . out .println( "In static block" ) ; } public static void method () { System . out .println( "In static method" ) ; } } package org.example.test3 ; public class Main { public static void main ( String [] args ) { Blocks . method () ; } } -> Class.forName() metodunu ishe salmaq: package org.example.test3 ; public class Blocks { static { System . out .println( "In static block" ) ; } } package org.example.test3 ; public class Main { public static void main ( String [] args ) throws Exception { Class . forName ( "org.example.test3.Blocks" ) ; } } -> non-static (instance) block: package org.example.test3 ; public class Blocks { static { System . out .println( "in static block" ) ; } { System . out .println( "in non static (instance) block
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