System

package SystemTest;

public class SystemTest {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		System.getProperties().list(System.out);
//		-- listing properties --
//		java.runtime.name=Java(TM) SE Runtime Environment
//		sun.boot.library.path=C:\Program Files\Java\jdk1.6.0_21\jre...
//		java.vm.version=17.0-b17
//		java.vm.vendor=Sun Microsystems Inc.
//		java.vendor.url=http://java.sun.com/
//		path.separator=;
//		java.vm.name=Java HotSpot(TM) Client VM
//		file.encoding.pkg=sun.io
//		user.country=CN
//		sun.java.launcher=SUN_STANDARD
//		sun.os.patch.level=Service Pack 2
//		java.vm.specification.name=Java Virtual Machine Specification
//		user.dir=E:\Server\test-one
//		java.runtime.version=1.6.0_21-b07
//		java.awt.graphicsenv=sun.awt.Win32GraphicsEnvironment
//		java.endorsed.dirs=C:\Program Files\Java\jdk1.6.0_21\jre...
//		os.arch=x86
//		java.io.tmpdir=C:\DOCUME~1\ADMINI~1\LOCALS~1\Temp\
//		line.separator=
//
//		java.vm.specification.vendor=Sun Microsystems Inc.
//		user.variant=
//		os.name=Windows XP
//		sun.jnu.encoding=GBK
//		java.library.path=C:\Program Files\Java\jdk1.6.0_21\bin...
//		java.specification.name=Java Platform API Specification
//		java.class.version=50.0
//		sun.management.compiler=HotSpot Client Compiler
//		os.version=5.1
//		user.home=C:\Documents and Settings\Administrator
//		user.timezone=
//		java.awt.printerjob=sun.awt.windows.WPrinterJob
//		file.encoding=UTF-8
//		java.specification.version=1.6
//		user.name=Administrator
//		java.class.path=E:\Server\test-one\build\classes;E:\S...
//		java.vm.specification.version=1.0
//		sun.arch.data.model=32
//		java.home=C:\Program Files\Java\jdk1.6.0_21\jre
//		java.specification.vendor=Sun Microsystems Inc.
//		user.language=zh
//		awt.toolkit=sun.awt.windows.WToolkit
//		java.vm.info=mixed mode, sharing
//		java.version=1.6.0_21
//		java.ext.dirs=C:\Program Files\Java\jdk1.6.0_21\jre...
//		sun.boot.class.path=C:\Program Files\Java\jdk1.6.0_21\jre...
//		java.vendor=Sun Microsystems Inc.
//		file.separator=\
//		java.vendor.url.bug=http://java.sun.com/cgi-bin/bugreport...
//		sun.cpu.endian=little
//		sun.io.unicode.encoding=UnicodeLittle
//		sun.desktop=windows
//		sun.cpu.isalist=pentium_pro+mmx pentium_pro pentium+m...
	}

}

 

gc

package SystemTest;

class Person{
	private String name ;
	private int age ;
	public Person(String name,int age){
		this.name = name ;
		this.age = age;
	}
	public String toString(){	// 覆写toString()方法
		return "姓名：" + this.name + "，年龄：" + this.age ;
	}
	public void finalize() throws Throwable{	// 对象释放空间时默认调用此方法
		System.out.println("对象被释放 --> " + this) ;
	}
};
public class SystemDemo04{
	public static void main(String args[]){
		Person per = new Person("张三",30) ;
		per = null ;	// 断开引用
		System.gc() ;		// 强制性释放空间
	}
};