Question

Given:

public static final String XML_POLICY =
            "<?xml version="1.0"?>"
            +"<!DOCTYPE cross-domain-policy SYSTEM "/xml/dtds/cross-domain-policy.dtd">"
            + "<cross-domain-policy>"
            + "<allow-access-from domain="*" to-ports="*" />"
            + "</cross-domain-policy>";

I am getting compile errors on the

"<?xml version="1.0"?>"

it says ‘;‘ expected.

and on

+"<!DOCTYPE cross-domain-policy SYSTEM "/xml/dtds/cross-domain-policy.dtd">"

it says “cannot find symbol, symbol: class xml and class dtds”

What could be the possible cause? IDE is Netbeans 6.8 Beta.

Answer 1

You need to escape the double quotes – and it’s not just the first line, either. The doctype and allow-access-from lines require it too.

// Reformatted slightly to avoid scrolling :)
public static final String XML_POLICY =
  "<?xml version=\"1.0\"?>"
  + "<!DOCTYPE cross-domain-policy SYSTEM \"/xml/dtds/cross-domain-policy.dtd\">"
  + "<cross-domain-policy>"
  + "<allow-access-from domain=\"*\" to-ports=\"*\" />"
  + "</cross-domain-policy>";

An alternative it to use single quotes within the XML, which is fine in most places, and makes the code simpler to read:

public static final String XML_POLICY =
    "<?xml version='1.0'?>"
    +"<!DOCTYPE cross-domain-policy SYSTEM '/xml/dtds/cross-domain-policy.dtd'>"
    + "<cross-domain-policy>"
    + "<allow-access-from domain='*' to-ports='*' />"
    + "</cross-domain-policy>";

Note that there’s nothing Netbeans or XML-specific about this. A double quote is used to indicate the start and end of a string, which is why you need to escape it if you want one in the middle. For example:

String x = "I said, \"Hello.\" The child laughed.";

There are various other escape sequences in Java – see section 3.10.6 of the language specification for more details.