JVM Tutorials - Herong's Tutorial Examples

∟java.lang.System Class - The Operating System

This chapter provides tutorial notes and example codes on java.lang.System class. Topics include accessing standard input, output, and error streams; getting the current time in milliseconds and nanoseconds; accessing environment variables; managing JVM instance properties.

What Is java.lang.System

Standard Input, Output, and Error Streams

Current Time in Milliseconds and Nanoseconds

Accessing System Environment Variables

Getting and Adding System Properties

Takeaways:

• java.lang.System is a built-in class that represents the operating system.
• in, out and err properties provides standard input, output, and error streams.
• nanoTime() method returns the current time in nanoseconds.
• getenv() method returns all environment variables defined in the operating system.
• getProperties() method returns all properties stored at the JVM instance level.

Table of Contents

 About This Book

 JVM (Java Virtual Machine) Specification

 Java HotSpot VM - JVM by Oracle/Sun

 java.lang.Runtime Class - The JVM Instance

►java.lang.System Class - The Operating System

 ClassLoader Class - Class Loaders

 Class Class - Class Reflections

 JVM Runtime Data Areas

 JVM Stack, Frame and Stack Overflow

 Thread Testing Program and Result

 CPU Impact of Multi-Thread Applications

 I/O Impact of Multi-Thread Applications

 CDS (Class Data Sharing)

 Micro Benchmark Runner and JVM Options

 Micro Benchmark Tests on "int" Operations

 Micro Benchmark Tests on "long" Operations

 Micro Benchmark Tests in JIT Compilation Mode

 Micro Benchmark Tests on "float" and "double" Operations

 OpenJ9 by Eclipse Foundation

 JRockit JVM 28.2.7 by Oracle Corporation

 Archived Tutorials

 References

 Full Version in PDF/EPUB

java.lang.System Class - The Operating System - Updated in 2024, by Herong Yang