I would recommend making Rock, Paper and Scissors objects. The objects would have the logic of both translating to/from Strings and also “knowing” what beats what. The Java enum is perfect for this. The parseType method can return null if the String is not a valid type. And you code can check if the value is null and if … Read more
Apart from an understanding of the accesses amongst modules and their respective packages. I believe the crux of it lies in the Module System#Relaxed-strong-encapsulation and I would just cherry-pick the relevant parts of it to try and answer the question. What defines an illegal reflective access and what circumstances trigger the warning? To aid in the migration … Read more
“Exception in thread “main” java.lang.IndexOutOfBoundsException: Index: 0, Size: 0″ is the main error I get when I compile this method: How can I fix this?
The reason behind this is that meanwhile creating your own class, you had also accepted to create a default class as prescribed by your IDE and after writing your code in your own class, you are getting such an error. In order to eliminate this, go to the PROJECT folder → src → Default package. Keep only … Read more
How should I declare main() method in Java? String[] and String… are the same thing internally, i. e., an array of Strings. The difference is that when you use a varargs parameter (String…) you can call the method like: And when you declare the parameter as a String array you MUST call this way: What’s actually the difference between String[] and String… if … Read more
You’ll find one in http://commons.apache.org/lang/ It’s called But it roughly does the same as yours. If you’re in for more precision, use
Is null an instance of anything? No, there is no type which null is an instanceof. 15.20.2 Type Comparison Operator instanceof At run time, the result of the instanceof operator is true if the value of the RelationalExpression is not null and the reference could be cast to the ReferenceType without raising a ClassCastException. Otherwise the result is false. This means that for any type E and R, for any E o, where o == null, o … Read more
Java 8 introduces a String.join(separator, list) method; see Vitalii Federenko’s answer. Before Java 8, using a loop to iterate over the ArrayList was the only option: DO NOT use this code, continue reading to the bottom of this answer to see why it is not desirable, and which code should be used instead: In fact, a string concatenation is going … Read more
Your algorithm is fine. However int is too small for your computations, it fails for this input: At some point integer overflows to negative value and your implementation goes crazy, recursing infinitely. Change int num to long num and you’ll be fine – for some time. Later you’ll need BigInteger. Note that according to Wikipedia on Collatz conjecture (bold mine): The longest progression for … Read more