我的第一个Java程序：

import java.util.Date;

import framework.Factory;
import framework.Product;
import idcard.IDCardFactory;

public class Main {
	public static void main(String[] args) {
		System.out.print("Hello It's:");
		System.out.println(new Date());
	}
}
//输出结果
//Hello It's:Thu Jan 17 10:51:58 CST 2019

演示Java的类库多样：

public class Main {
	public static void main(String[] args) {
		//输出系统所有信息
		System.getProperties().list(System.out);
		//输出指定信息
		System.out.println(System.getProperty("os.name"));
	}
}
/* 第一个输出：
-- listing properties --
sun.desktop=windows
awt.toolkit=sun.awt.windows.WToolkit
java.specification.version=10
file.encoding.pkg=sun.io
sun.cpu.isalist=amd64
sun.jnu.encoding=GBK
java.class.path=C:\Users\Administrator\eclipse-worksp...
java.vm.vendor="Oracle Corporation"
sun.arch.data.model=64
user.variant=
java.vendor.url=http://java.oracle.com/
user.timezone=
os.name=Windows 7
java.vm.specification.version=10
sun.java.launcher=SUN_STANDARD
user.country=CN
sun.boot.library.path=D:\JAVA\bin
sun.java.command=Main
jdk.debug=release
sun.cpu.endian=little
user.home=C:\Users\Administrator
user.language=zh
java.specification.vendor=Oracle Corporation
java.version.date=2018-07-17
java.home=D:\JAVA
file.separator=\
java.vm.compressedOopsMode=32-bit
line.separator=

java.specification.name=Java Platform API Specification
java.vm.specification.vendor=Oracle Corporation
java.awt.graphicsenv=sun.awt.Win32GraphicsEnvironment
user.script=
sun.management.compiler=HotSpot 64-Bit Tiered Compilers
java.runtime.version=10.0.2+13
user.name=Administrator
path.separator=;
os.version=6.1
java.runtime.name=Java(TM) SE Runtime Environment
file.encoding=GBK
java.vm.name=Java HotSpot(TM) 64-Bit Server VM
java.vendor.version=18.3
java.vendor.url.bug=http://bugreport.java.com/bugreport/
java.io.tmpdir=C:\Users\ADMINI~1\AppData\Local\Temp\
java.version=10.0.2
user.dir=C:\Users\Administrator\eclipse-worksp...
os.arch=amd64
java.vm.specification.name=Java Virtual Machine Specification
java.awt.printerjob=sun.awt.windows.WPrinterJob
sun.os.patch.level=
java.library.path=D:\JAVA\bin;C:\windows\Sun\Java\bin;C...
java.vendor=Oracle Corporation
java.vm.info=mixed mode
java.vm.version=10.0.2+13
sun.io.unicode.encoding=UnicodeLittle
java.class.version=54.0
*/

//第二个输出   Windows 7