What Is java.lang.System

This section describes what is java.lang.System - A Java built-in class that presents the operating system where the Java Virtual Machine (JVM) is running.

What Is java.lang.System? java.lang.System is a built-in class that presents the operating system where the Java Virtual Machine (JVM) is running.

java.lang.System class allows the application to interface with the operating system in which the JVM is running through these static properties and static methods:

java.lang.System class also provides some methods that are equivalent to those on the JVM Runtime instance for quick access:

Tutorial example programs are provided in next sections to test those properties and methods.

Last update: 2014.

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

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

 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

 JRockit JVM 28.2.7 by Oracle Corporation

 Outdated Tutorials

 References

 Full Version in PDF/EPUB