import java.io.InputStream;
import java.net.URL;
import sun.misc.BASE64Encoder;

public class Main {
    
    public static void main(String[] args) {
        String imageUrl = "https://ebanking1.ccb.com.cn/NCCB_Encoder/Encoder?CODE=EjnWhSHHlQplStLLUQ1SQZHvEA1lQmXcoA11R2nglvVgR66ChUmGWF3OIV6xS1HdEl4USJHCkc1VQWXdUn5ERrHhg0DdkI";
        try{
            String encoder = "data:image/jpg;base64,";
            URL url = new URL(imageUrl);
            InputStream inputStream = url.openStream();
            int length = inputStream.available();
            byte[] byteArr = new byte[length];
            inputStream.read(byteArr);
            inputStream.close();
            
            BASE64Encoder base64Encoder = new BASE64Encoder();
            encoder = base64Encoder.encode(byteArr);
            System.out.println(encoder);
        }catch(Exception e){
            e.printStackTrace();
        }
    }
}

import java.io.InputStream;
import java.net.URL;
import java.util.Base64;

public class Main {

    public static void main(String[] args) {
        String imageUrl = "https://ebanking1.ccb.com.cn/NCCB_Encoder/Encoder?CODE=EjnWhSHHlQplStLLUQ1SQZHvEA1lQmXcoA11R2nglvVgR66ChUmGWF3OIV6xS1HdEl4USJHCkc1VQWXdUn5ERrHhg0DdkI";
        try{
            String pre = "data:image/jpg;base64,";
            URL url = new URL(imageUrl);
            InputStream inputStream = url.openStream();
            int length = inputStream.available();
            byte[] byteArr = new byte[length];
            inputStream.read(byteArr);
            inputStream.close();
            Base64.Encoder encoder = Base64.getEncoder();
            // 将字节数组转换base64
            String encodeToString = encoder.encodeToString(byteArr);
            System.out.println(pre+encodeToString);
        }catch(Exception e){
            e.printStackTrace();
        }
    }
}