4月8日，DemogetProperties，每日20行。

import java.util.*;
public class DemogetProperties {

    public static void main(String[] args) {
        Properties sp = System.getProperties();
        Enumeration e = sp.propertyNames();
        while(e.hasMoreElements()){
            String key = (String)e.nextElement();
            System.out.println(key + " = " + sp.getProperty(key));
        }
    }

}