Java is one of the most popular programming languages in the world and is widely used for web applications, mobile apps, enterprise software, and backend systems. One question that often confuses beginners is:
Why is Java called both a compiled and an interpreted language?
At first, this may sound confusing because programming languages are usually classified as either compiled or interpreted. However, Java follows a unique execution process that combines both approaches. This blog explains the concept in simple and clear language.
Understanding the Basics First
Before explaining Java’s behavior, it is important to understand what compiled and interpreted languages mean.
What Is a Compiled Language?
In a compiled language:
- The entire source code is converted into machine code at once
- Compilation happens before the program runs
- The compiled file runs directly on the system
Examples of compiled languages include C and C++.
What Is an Interpreted Language?
In an interpreted language:
- Code is executed line by line
- No separate machine code file is created
- Execution happens during runtime
Examples include Python and JavaScript.
Where Does Java Fit In?
Java does not fall completely into either category. Instead, Java uses both compilation and interpretation. That is why Java is called a compiled and interpreted language.
To understand this clearly, let’s look at how Java programs are executed.
Step-by-Step Java Execution Process
Step 1: Writing Java Source Code
A Java program is written in a .java file using human-readable syntax. This is where learners usually begin by understanding concepts, logic, and syntax through a Java Tutorial.
Step 2: Compilation Using Java Compiler
The Java compiler (javac) converts the source code into an intermediate form called bytecode.
Important points:
- Bytecode is not machine-specific
- It is saved in a .class file
- Syntax errors are checked at compile time
This step proves that Java is a compiled language.
Step 3: Interpretation by JVM
The bytecode is executed by the Java Virtual Machine (JVM).
What the JVM does:
- Reads bytecode instructions
- Converts them into machine code
- Executes them at runtime
Since execution happens during runtime, Java is also considered an interpreted language.
Role of the Java Virtual Machine (JVM)
The JVM is the main reason Java is both compiled and interpreted.
The JVM:
- Loads and verifies bytecode
- Ensures security
- Converts bytecode to machine code
- Manages memory automatically
Because JVMs exist for different operating systems, Java programs can run on multiple platforms without modification.
Why Java Uses Both Compilation and Interpretation
Java was designed with several goals in mind.
Platform Independence
Java follows the principle Write Once, Run Anywhere. Bytecode allows Java programs to run on any system that has a JVM.
Better Security
Before execution, bytecode is verified to prevent unsafe operations, illegal memory access, and malicious code execution.
Improved Performance
Modern JVMs use Just-In-Time (JIT) compilation. Frequently used bytecode is converted into native machine code, making Java faster than traditional interpreted languages.
Is Java Fully Interpreted?
No. Java does not execute source code directly. It must be compiled into bytecode first.
Is Java Fully Compiled?
No. Java does not compile directly into machine-specific code. Execution always depends on the JVM.
Why Java Is Called Both Compiled and Interpreted
Java is called a compiled and interpreted language because:
- Source code is compiled into bytecode
- Bytecode is interpreted and executed by the JVM at runtime
Both steps are essential in Java’s execution process.
Java Compilation vs Execution Comparison
Compilation
- Happens before execution
- Converts source code into bytecode
- Detects syntax errors
Interpretation
- Happens during execution
- JVM converts bytecode into machine code
- Handles runtime errors
How Beginners Can Practice Java Execution
To understand Java execution practically, many beginners use an Online Java Compiler. It allows learners to write, compile, and run Java code instantly without installing software. This helps focus on logic rather than setup.
Common Misconceptions About Java
Java is only interpreted – Incorrect. Java is compiled first.
Java is slow – Not true. JIT compilation improves performance.
JVM and compiler are the same – Incorrect. The compiler creates bytecode, while the JVM executes it.
Advantages of Java’s Execution Model
- Platform independence
- Strong security
- Automatic memory management
- Better performance optimization
- Easy debugging and maintenance
Final Conclusion
Java is called a compiled and interpreted language because it combines both techniques. The source code is compiled into bytecode, and the bytecode is interpreted and executed by the JVM.
This hybrid approach gives Java portability, security, performance, and long-term reliability, which is why Java remains one of the most trusted programming languages today.
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