Week 76 — What is Java bytecode and why is it needed?
Question of the Week #76
What is Java bytecode and why is it needed?
8 Replies
JVM bytecode is an intermediate language which can be read and executed by the JVM. Java source code is compiled to bytecode using the
javac program and that bytecode can then be executed using java. The bytecode can then be optimized compiled to machine-code automatically at runtime using the JIT compiler(s).
In contrast to many other compiled languages like C or C++, Java code is typically not directly compiled to machine code (which is specific to the Operating System/architecture). Instead, it is compiled to a platform-independent representation called bytecode. This can then be run using the java command independently of the Operating System or architecture used when running the application (The same bytecode can be run on any Operating System/architecture as long as a compatible JRE is installed).
While source code is made for developers, it is not that easy for computers to interpret/directly execute. Bytecode provides a machine-independent instruction set that can be loaded efficiently. Furthermore, it is language-independent meaning that other languages (e.g. Kotlin) can compile to JVM bytecode as well.
JVM bytecode is (typically) contained in .class files. These files contain information about some type (a class, interface, record, enum etc.) and its members as well as the actual bytecode containing instructions on how to run methods declared in that type. Information about the bytecode and class file format can be found in the JVM Specification: https://docs.oracle.com/javase/specs/jvms/se21/html/index.html📖 Sample answer from dan1st
Java uses bytecode for platform independence, security, and performance. It runs on any Java Virtual Machine (JVM), ensuring portability and consistency.
Submission from alsaleeh
Java byte code is a machine language, which is generated after compilation of java code which can be run on any machine which is stored in Java Virtual Machine( JVM). Because if Java Byte code java is independent of machines.
it's like : 0101010010 which can be only understand by mahcines it is not human readable.
Submission from chandrashekhar_
Bytecode is an intermediate language code which can run on any operation system with a JVM installed in it. It is created by the javac after compiling the source code written in java language. It is needed because it is the feature that makes java platform independent
Submission from referral0607
Bytecode Is basically machine language of the JVM and JVM translate it into binary so that computer can understand it
Submission from longrang3
Bytecode is the platform-neutral binary "machine code" that is created when Java (and other JVM languages) are compiled. The result of this compilation is written to
.class files, which can then be loaded by the JVM for program execution. In this way, bytecode is analogous to native machine code (such as would be produced by a C compiler/linker), but the execution target is the JVM, rather than a specific hardware architecture/operating system combo. The JVM, then, acts as the "bridge" between the bytecode and platform-specific instructions.The bytecode is the means by which Java achieves it's platform-independence ("write once, run anywhere"). The same set of
.class files can be distributed to any computing device for which a JVM exists, and the software will run identically across each of them.⭐ Submission from dangerously_casual