import java.util.*;class SystemDemo {public static void main(String[] args) {Properties prop=System.getProperties();for (Object obj:prop.keySet() ){ String value=(String)prop.get(obj);System.out.println(obj+":"+value);}}}

import java.util.*;class SystemDemo {public static void main(String[] args) {Properties prop=System.getProperties();for (Object obj:prop.keySet() ){ String value=(String)prop.get(obj);System.out.println(obj+":"+value);}}}
import java.util.*;
class SystemDemo
{
public static void main(String[] args)
{
Properties prop=System.getProperties();
for (Object obj:prop.keySet() )
{
String value=(String)prop.get(obj);
System.out.println(obj+":"+value);
}
}
}

import java.util.*;class SystemDemo {public static void main(String[] args) {Properties prop=System.getProperties();for (Object obj:prop.keySet() ){ String value=(String)prop.get(obj);System.out.println(obj+":"+value);}}}
一个介词,在中文里相当于“为”“为了”“属于谁的.”

for+一段时间
eg:I am staying for a week.