Thinking in Java里这段代码的意思是什么？

import java.util.*;
public class Property {
public static void main(String[] args){
System.out.println(new Date());
Properties p = System.getProperties();
p.list(System.out);
System.out.println("--- Memory Usage:");
Runtime rt = Runtime.getRuntime();
System.out.println("Total Memory = "
+ rt.totalMemory()
+ " Free Memory = "
+ rt.freeMemory());
}
}
希望能分析一下每一句的作用和意思，谢谢！

import java.util.*;
public class Property {
public static void main(String[] args){
System.out.println(new Date());
Properties p = System.getProperties();
p.list(System.out);
System.out.println("--- Memory Usage:");
Runtime rt = Runtime.getRuntime();
System.out.println("Total Memory = "
+ rt.totalMemory()
+ " Free Memory = "
+ rt.freeMemory());
}