Java Runtime Basics
What is Java Runtime Environment (JRE)?
Java Runtime Environment (JRE) is a crucial software package that enables running Java applications on a computer. It provides the necessary runtime libraries, Java Virtual Machine (JVM), and other components required to execute Java programs.
Key Components of Java Runtime
Java Virtual Machine (JVM)
The JVM is the core component of the Java runtime that interprets and executes Java bytecode. It provides:
- Platform independence
- Memory management
- Security features
graph TD
A[Java Source Code] --> B[Java Compiler]
B --> C[Bytecode]
C --> D[JVM]
D --> E[Machine Code Execution]
Runtime Libraries
Java provides a comprehensive set of standard libraries that support various programming tasks:
Library Category |
Purpose |
java.lang |
Core language functionality |
java.util |
Utility classes and data structures |
java.io |
Input/Output operations |
java.net |
Network programming |
Installing JRE on Ubuntu
To install Java Runtime Environment on Ubuntu 22.04, use the following command:
sudo apt update
sudo apt install default-jre
Verifying Java Installation
After installation, verify the Java version:
java --version
Runtime Environment Configuration
JAVA_HOME Environment Variable
Setting the JAVA_HOME environment variable helps applications locate the Java installation:
export JAVA_HOME=/usr/lib/jvm/java-11-openjdk-amd64
export PATH=$PATH:$JAVA_HOME/bin
The JRE manages system resources dynamically, including:
- Memory allocation
- Garbage collection
- Thread management
LabEx Learning Tip
At LabEx, we recommend practicing Java runtime concepts through hands-on exercises to build a solid understanding of how Java applications execute.