//如果在程序中要频繁的改变整数值，则不要用Integer，
//而应该使用int
//得到JVM的属性集
Properties pro=System.getProperties();
Set set=pro.keySet();
Iterator it=set.iterator();
while(it.hasNext()){
Object obj=it.next();
System.out.println(obj+"="+pro.get(obj));
}
System.out.println("========================");
//得到操作系统的环境变量
Map map=System.getenv();
Set set2=map.keySet();
Iterator it2=set2.iterator();
while(it2.hasNext()){
Object obj=it2.next();
System.out.println(obj+"="+map.get(obj));
}
Set set=map.keySet();
Iterator it=set.iterator();
while(it.hasNext()){
Object key=it.next();
System.out.println(key+":"+map.get(key));
}
System.out.println("======================");
Set set2=map.entrySet();
Iterator it2=set2.iterator();
while(it2.hasNext()){
Object obj=it2.next();
Map.Entry ent=(Map.Entry)obj;
System.out.println(ent.getKey()+":"+ent.getValue());
}