The ASCII table is arranged so that the value of the character ‘9’ is nine greater than the value of ‘0’; the value of the character ‘8’ is eight greater than the value of ‘0’; and so on. So you can get the int value of a decimal digit char by subtracting ‘0’.
In simple terms, a stack trace is a list of the method calls that the application was in the middle of when an Exception was thrown. Simple Example With the example given in the question, we can determine exactly where the exception was thrown in the application. Let’s have a look at the stack trace: … Read more
Neither of them. If you define it, it’s not the default. The default constructor is the no-argument constructor automatically generated unless you define another constructor. Any uninitialised fields will be set to their default values. For your example, it would look like this assuming that the types are String, int and int, and that the … Read more
I am porting a C++ library to Java and I need a heap data structure. Is there a standard implementation or will I need to do it myself?
Since Java 5 you can use Arrays.toString(arr) or Arrays.deepToString(arr) for arrays within arrays. Note that the Object[] version calls .toString() on each object in the array. The output is even decorated in the exact way you’re asking. Examples: Simple Array: String[] array = new String[] {“John”, “Mary”, “Bob”}; System.out.println(Arrays.toString(array)); Output: [John, Mary, Bob] Nested Array: … Read more
I’m trying to use the char method isLetter(), which is supposed to return boolean value corresponding to whether the character is a letter. But when I call the method, I get an error stating that “char cannot be dereferenced.” I don’t know what it means to dereference a char or how to fix the error. … Read more
The “common knowledge” of programming is that x += y is an equivalent shorthand notation of x = x + y. As long as x and y are of the same type (for example, both are ints), you may consider the two statements equivalent. However, in Java, x += y is not identical to x … Read more
I have installed an application, when I try to run it (it’s an executable jar) nothing happens. When I run it from the commandline with: java -jar “app.jar” I get the following message: no main manifest attribute, in “app.jar” Normally, if I had created the program myself, I would have added a main class attribute … Read more
In chapter 3.5 , it illustrates the protected modifier with the following words: More precisely, beyond being accessible within the class itself and to code within the same package, a protected member can also be accessed from a class through object references that are of at least the same type as the class that is, … Read more
Actually, probably the “best” way to initialize the ArrayList is the method you wrote, as it does not need to create a new List in any way: The catch is that there is quite a bit of typing required to refer to that list instance. There are alternatives, such as making an anonymous inner class … Read more