java错误非静态方法encode（byte []）不能从静态上下文中引用

Question

package com.cordys.report;
import java.io.FileInputStream; 
import org.apache.commons.codec.binary.Base64;

public class Encode 
{
    public static String encodeFileStream(String filePath) //file path ex : C:\Program Files\Cordys\Web\reports\I0001180.pdf
    {    
        try 
        {
            FileInputStream fin = new FileInputStream("E:/CSS Document/Test.pdf");
            StringBuffer sb = new StringBuffer();
            int lineLength = 72;
            byte[] buf = new byte[lineLength/4*3];

            while (true) 
            {
                int len = fin.read(buf);
                if (len <= 0) {
                    break;
                }

                //new Base64().encode(byte);
                sb.append(Base64.encode(buf));
                //sb.append(Base64.encodeBase64(buf));

                return sb.toString();
            }
        }  
        catch(Exception e) 
        {
            return e.getMessage();
        }
    }
}