java 基础之枚举

public enum SingletonPropsByEnum {
    INSTANCE;
    
    private Properties properties;
    private InputStream in;
    
    private SingletonPropsByEnum(){
        in = this.getClass().getResourceAsStream("/System.properties");  //注意,这里不能改成参数的形式!!!,因为会初始化一次.
        properties = new Properties();                                    
    }
    
    public Properties getProperties() throws IOException{
        properties.load(in);
        return properties;
    }
}