Properties pro = new Properties();
FileInputStream in = new FileInputStream("a.properties");
pro.load(in);
in.close();

FileOutputStream oFile = new FileOutputStream(file, "a.properties");
pro.store(oFile, "Comment");
oFile.close();

import java.io.BufferedInputStream;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.InputStream; 
import java.util.Iterator;
import java.util.Properties; 

public class PropertyTest {
  public static void main(String[] args) { 
    Properties prop = new Properties();   
    try{
      //读取属性文件a.properties
      InputStream in = new BufferedInputStream (new FileInputStream("a.properties"));
      prop.load(in);   ///加载属性列表
      Iterator<String> it=prop.stringPropertyNames().iterator();
      while(it.hasNext()){
        String key=it.next();
        System.out.println(key+":"+prop.getProperty(key));
      }
      in.close();
      
      ///保存属性到b.properties文件
      FileOutputStream oFile = new FileOutputStream("b.properties", true);//true表示追加打开
      prop.setProperty("phone", "10086");
      prop.store(oFile, "The New properties file");
      oFile.close();
    }
    catch(Exception e){
      System.out.println(e);
    }
  } 
}