src目录下建三个文件分别为my.properties,my_en_US.properties,my_zh_CN.properties

下面的方法直接在main方法中运行

//获取src目录下my.properties文件中key为first的值
ResourceBundle r1 = ResourceBundle.getBundle("my",new Locale("",""));
//获取src目录下my_en_US.properties文件中key为first的值
ResourceBundle r2 = ResourceBundle.getBundle("my",new Locale("en","US"));
//获取src目录下my_zh_CN.properties文件中key为first的值
ResourceBundle r3 = ResourceBundle.getBundle("my",new Locale("zh","CN"));
System.out.println(r1.getString("first"));