Is Java a Compiled or an Interpreted programming language

Question

In the past I have used C   as a programming language  I know that the code written in C   goes through a compilation process until it becomes  object code  machine code    I would like to know how Java works in that respect  How is the user written Java code run by the computer

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Java is a compiled programming language  but rather than compile straight to executable machine code  it compiles to an intermediate binary form called JVM byte code  The byte code is then compiled and or interpreted to run the program

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Java implementations typically use a two-step compilation process  Java source code is compiled down to bytecode by the Java compiler  The bytecode is executed by a Java Virtual Machine  JVM   Modern JVMs use a technique called Just-in-Time  JIT  compilation to compile the bytecode to native instructions understood by hardware CPU on the fly at runtime   Some implementations of JVM may choose to interpret the bytecode instead of JIT compiling it to machine code  and running it directly   While this is still considered an  interpreter    It s quite different from interpreters that read and execute the high level source code  i e  in this case  Java source code is not interpreted directly  the bytecode  output of Java compiler  is     It is technically possible to compile Java down to native code ahead-of-time and run the resulting binary  It is also possible to interpret the Java code directly     To summarize  depending on the execution environment  bytecode can be    compiled ahead of time and executed as native code  similar to most C   compilers  compiled just-in-time and executed interpreted directly executed by a supported processor  bytecode is the native instruction set of some CPUs

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Java is compiled to bytecode  which then goes into the Java VM  which interprets it

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Code written in Java is    First compiled to bytecode by a program called javac as shown in the left section of the image above  Then  as shown in the right section of the above image  another program called java starts the Java runtime environment and it may compile and or interpret the bytecode by using the Java Interpreter JIT Compiler      When does java interpret the bytecode and when does it compile it  The application code is initially interpreted  but the JVM monitors which sequences of bytecode are frequently executed and translates them to machine code for direct execution on the hardware  For bytecode which is executed only a few times  this saves the compilation time and reduces the initial latency  for frequently executed bytecode  JIT compilation is used to run at high speed  after an initial phase of slow interpretation  Additionally  since a program spends most time executing a minority of its code  the reduced compilation time is significant  Finally  during the initial code interpretation  execution statistics can be collected before compilation  which helps to perform better optimization

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Quotation from  https   blogs oracle com ask-arun entry run your java applications faster     Application developers can develop the application code on any of the various OS that are available in the market today  Java language is agnostic at this stage to the OS  The brilliant source code written by the Java Application developer now gets compiled to Java Byte code which in the Java terminology is referred to as Client Side compilation  This compilation to Java Byte code is what enables Java developers to    write once     Java Byte code can run on any compatible OS and server  hence making the source code agnostic of OS Server  Post Java Byte code creation  the interaction between the Java application and the underlying OS Server is more intimate  The journey continues - The enterprise applications framework executes these Java Byte codes in a run time environment which is known as Java Virtual Machine  JVM  or Java Runtime Environment  JRE   The JVM has close ties to the underlying OS and Hardware because it leverages resources offered by the OS and the Server  Java Byte code is now compiled to a machine language executable code which is platform specific  This is referred to as Server side compilation    So I would say Java is definitely a compiled language

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Java does both compilation and interpretation   In Java  programs are not compiled into executable files  they are compiled into bytecode  as discussed earlier   which the JVM  Java Virtual Machine  then interprets   executes at runtime  Java source code is compiled into bytecode when we use the javac compiler  The bytecode gets saved on the disk with the file extension  class    When the program is to be run  the bytecode is converted the bytecode may be converted  using the just-in-time  JIT  compiler  The result is machine code which is then fed to the memory and is executed   Javac is the Java Compiler which Compiles Java code into Bytecode  JVM is Java Virtual Machine which Runs  Interprets  translates Bytecode into Native Machine Code  In Java though it is considered as an interpreted language  It may use JIT  Just-in-Time  compilation when the bytecode is in the JVM  The JIT compiler reads the bytecodes in many sections  or in full  rarely  and compiles them dynamically into machine code so the program can run faster  and then cached and reused later without needing to be recompiled  So JIT compilation combines the speed of compiled code with the flexibility of interpretation   An interpreted language is a type of programming language for which most of its implementations execute instructions directly and freely  without previously compiling a program into machine-language instructions  The interpreter executes the program directly  translating each statement into a sequence of one or more subroutines already compiled into machine code   A compiled language is a programming language whose implementations are typically compilers  translators that generate machine code from source code   and not interpreters  step-by-step executors of source code  where no pre-runtime translation takes place   In modern programming language implementations like in Java  it is increasingly popular for a platform to provide both options

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The terms  interpreted language  or  compiled language  don t make sense  because any programming language can be interpreted and or compiled   As for the existing implementations of Java  most involve a compilation step to bytecode  so they involve compilation  The runtime also can load bytecode dynamically  so some form of a bytecode interpreter is always needed  That interpreter may or may not in turn use compilation to native code internally   These days partial just-in-time compilation is used for many languages which were once considered  interpreted   for example JavaScript

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Kind of both  Firstly java compiled some would prefer to say  translated   to bytecode  which then either compiled  or interpreted depending on mood of JIT

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Java is a byte-compiled language targeting a platform called the Java Virtual Machine which is stack-based and has some very fast implementations on many platforms

[java] Is Java a Compiled or an Interpreted programming language ?

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