Question

I am using this code to read data from a webpage :

public class ReadLatex {
public static void main(String[] args) throws IOException {
    String urltext = "http://chart.apis.google.com/chart?cht=tx&chl=1+2%20\frac{3}{4}";
    URL url = new URL(urltext);
    BufferedReader in = new BufferedReader(new InputStreamReader(url
            .openStream()));
    String inputLine;

    while ((inputLine = in.readLine()) != null) {
        // Process each line.
        System.out.println(inputLine);
    }
    in.close();
   }
}

The webpage gives the image for a latex code in the URL.

I am getting this exception:

Exception in thread "main" java.io.IOException: Server returned HTTP response code: 400 for URL: http://chart.apis.google.com/chart?
at sun.net.www.protocol.http.HttpURLConnection.getInputStream(Unknown Source)
at java.net.URL.openStream(Unknown Source)
at ReadLatex.main(ReadLatex.java:11)

Can anyone tell why I am having this problem and what should be the solution for this?

Answer 1

Your problem is that you are using a \ (backslash) in a string which in Java is a escape character. To get an actual \ you need to have two of them in your string. So:

Wanted text: part1\part2

you need to have

String theString = "part1\\part2";

So you actually want

String urltext = "http://chart.apis.google.com/chart?cht=tx&chl=1+2%20\\frac{3}{4}";

Also, when you succeed with your request you get back an image (png) which should not be read with a reader which will try to interpret the bytes as characters using some encoding and this will break the image data. Instead, use the input stream and write the content (bytes) to a file.

A simple example without error handling

public static void main(String[] args) throws IOException {
    String urltext = "http://chart.apis.google.com/chart?cht=tx&chl=1+2%20\\frac{3}{4}";
    URL url = new URL(urltext);

    InputStream in = url.openStream();
    FileOutputStream out = new FileOutputStream("TheImage.png");

    byte[] buffer = new byte[8*1024];
    int readSize;
    while ( (readSize = in.read(buffer)) != -1) {
        out.write(buffer, 0, readSize);
    }
    out.close();
    in.close();
}