java.lang.System : 系统类 « 开发相关 « Java 教程

6. 1. 1. java.lang.System

The System class is a final class that exposes useful static fields. The static methods can help you with common tasks.

The out field represents the standard output stream which by default is the same console.


public class MainClass {



  public static void main(String[] args) {

    String message = "qwer";

    System.out.print(message);



  }



}

6. 1. 系统类
	6. 1. 1.	java.lang.System
	6. 1. 2.	PrintStream has many print method overloads that accept different types
	6. 1. 3.	println增加了行终止结束符
	6. 1. 4.	The err field represents a PrintStream object
	6. 1. 5.	The 'in' field represents the standard input stream
	6. 1. 6.	数组复制方法
	6. 1. 7.	终止正在运行的程序
	6. 1. 8.	以毫秒为单位返回计算机的时间
	6. 1. 9.	public static long nanoTime(): provide more precision, i.e. in nanoseconds
	6. 1. 10.	Using System.getProperty(String key) to retrieve system properties
	6. 1. 11.	当前登录到计算机取得名称的用户
	6. 1. 12.	Create a user-defined property or change the value of the current property
	6. 1. 13.	Returns a default value if the specified property does not exist
	6. 1. 14.	将返回所有系统属性
	6. 1. 15.	退出了一个Java程序
	6. 1. 16.	使用系统类终止虚拟机
	6. 1. 17.	输出重定向到一个文件。
	6. 1. 18.	计算过程运行的时间

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