Properties类的简单问题

Question

程序不能编译：出现1个错误prop.setProperty("property1"+"newValue1");知道的帮忙看下，谢谢
import java.util.*;
import java.io.*;
public class LoadProperty
{public static void main(String args[]) throws Exception
{Properties prop=new Properties();
FileInputStream fis=new FileInputStream("properties.txt");
prop.load(fis);
prop.list(System.out);
System.out.println("The property1 property:"+prop.getProperty("property1"));
prop.setProperty("property1"+"newValue1");
System.out.println("after set new value");
System.out.println("The property1 new property:"+prop.getProperty("property1"));
        }
}

Answer 1

prop.setProperty("property1"+"newValue1");
==>
prop.setProperty("property1","newValue1");