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How can we match a^n b^n with Java regex?
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The answer is, needless to say, YES! You can most certainly write a Java regex pattern to match anbn. It uses a positive lookahead for assertion, and one nested reference for "counting".
Rather than immediately giving out the pattern, this answer will guide readers through the process of deri...
Type safety: Unchecked cast
...re would not be a warning in the first case, I'm not sure how pedantic the Java compiler is with warnings for Java 5). However, you are converting it to a HashMap<String, String>.
HashMaps are really maps that take an object as a key and have an object as a value, HashMap<Object, Object>...
How do I make HttpURLConnection use a proxy?
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Since java 1.5 you can also pass a java.net.Proxy instance to the openConnection(proxy) method:
//Proxy instance, proxy ip = 10.0.0.1 with port 8080
Proxy proxy = new Proxy(Proxy.Type.HTTP, new InetSocketAddress("10.0.0.1", 8080))...
Declaring and initializing variables within Java switches
I have a crazy question about Java switches.
6 Answers
6
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Why do this() and super() have to be the first statement in a constructor?
Java requires that if you call this() or super() in a constructor, it must be the first statement. Why?
19 Answers
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Pretty-Print JSON in Java
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If you are using a Java API for JSON Processing (JSR-353) implementation then you can specify the JsonGenerator.PRETTY_PRINTING property when you create a JsonGeneratorFactory.
The following example has been originally published on my blog pos...
Google Gson - deserialize list object? (generic type)
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Method to deserialize generic collection:
import java.lang.reflect.Type;
import com.google.gson.reflect.TypeToken;
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Type listType = new TypeToken<ArrayList<YourClass>>(){}.getType();
List<YourClass> yourClassList = new Gson().fromJson(jsonArray, listT...
How to round a number to n decimal places in Java
... first looked at the DecimalFormat class is that it was only introduced in Java 1.6. Unfortunately I'm restricted to using 1.5 but it will be useful to know for the future.
– Alex Spurling
Oct 1 '08 at 13:07
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PatternSyntaxException: Illegal Repetition when using regex in Java
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The { and } are special in Java's regex dialect (and most other dialects for that matter): they are the opening and closing tokens for the repetition quantifier {n,m} where n and m are integers. Hence the error message: "Illegal repetition".
You shoul...
Cannot issue data manipulation statements with executeQuery()
...() rather than executeQuery().
Here's an extract from the executeUpdate() javadoc which is already an answer at its own:
Executes the given SQL statement, which may be an INSERT, UPDATE, or DELETE statement or an SQL statement that returns nothing, such as an SQL DDL statement.
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