Java finding substring

I have the following String:

oauth_token=safcanhpyuqu96vfhn4w6p9x&**oauth_token_secret=hVhzHVVMHySB**&application_name=Application_Name&login_url=https%3A%开发者_运维技巧2F%2Fapi-user.netflix.com%2Foauth%2Flogin%3Foauth_token%3Dsafcanhpyuqu96vfhn4w6p9x

I am trying to parse out the value for oauth_token_secret. I need everything from the equals sign (=) to the next ampersand sign (&). So I need to parse out: hVhzHVVMHySB

Currently, I have the following code:

Const.OAUTH_TOKEN_SECRET = "oauth_token_secret";

Const.tokenSecret = 
  content.substring(content.indexOf((Const.OAUTH_TOKEN_SECRET + "="))
    + (Const.OAUTH_TOKEN_SECRET + "=").length(), 
      content.length());

This will start at the beginning of the oauth_token_string, but it will not stop at the next ampersand. I am unsure how to specify to stop at the end of the following ampersand. Can anyone help me?

The indexOf() methods allow you to specify an optional fromIndex. This allows you to find the next ampersand:

int oauth = content.indexOf(Const.OAUTH_TOKEN_SECRET);
if (oauth != -1) {
  int start = oath + Const.OATH_TOKEN_SECRET.length(); // or
  //int start = content.indexOf('=', oath) + 1;
  int end = content.indexOf('&', start);
  String tokenSecret = end == -1 ? content.substring(start) : content.substring(start, end);
}

public static Map<String, String> buildQueryMap(String query)  
{  
  String[] params = query.split("&");  
  Map<String, String> map = new HashMap<String, String>();  
  for (String param : params)  
  {
    String[] pair = param.split("=");
    String name = pair[0];  
    String value = pair[1];  
    map.put(name, value);  
  }  
  return map;  
}

// in your code
Map<String, String> queryMap = buildQueryMap("a=1&b=2&c=3....");
String tokenSecret = queryMap.get(Const.OAUTH_TOKEN_SECRET);

Using String.split gives a much cleaner solution.

static String getValue(String key, String content) {
  String[] tokens = content.split("[=&]");
  for(int i = 0; i < tokens.length - 1; ++i) {
    if(tokens[i].equals(key)) {
      return tokens[i+1];
    }
  }
  return null;
}

Click here for a test drive! ;-)

A much better solution is using the Pattern and corresponding Matcher class.

By using a capturing group you can check and "cut out" the the appropriate substring in one step.