Java queues don’t have enqueue and dequeue methods, these operations are done using the following methods: Enqueuing: add(e): throws exception if it fails to insert the object offer(e): returns false if it fails to insert the object Dequeuing: remove(): throws exception if the queue is empty poll(): returns null if the queue is empty Take … Read more
What is an immutable object? An immutable object is one that will not change state after it is instantiated. How to make an object immutable? In general, an immutable object can be made by defining a class which does not have any of its members exposed, and does not have any setters. The following class … Read more
It looks like your XML document has the root element “Group” instead of “group”. You can: Change the root element on your XML to be “group” Add the annotation @XmlRootElement(name=”Group”) to the Group classs.
I have two questions about Exceptions. Firstly, I got this message from my code… This error message means dividing by zero, such as by doing int a = 5 / 0; A method can throw an Exception class instance, can’t it? But this is an expression. Why can an expression throw an Exception class instance … Read more
I am completely stumped. I took a break for a few hours and I can’t seem to figure this one out. It’s upsetting! I know that I need to check the current element in the array and see if it appears elsewhere in the array. The idea is to output the following: The user is … Read more
From the discussion here, and especially this answer, this is the function I currently use: My own tiny benchmarks (a million bytes a thousand times, 256 bytes 10 million times) showed it to be much faster than any other alternative, about half the time on long arrays. Compared to the answer I took it from, … Read more
You need to use the relational operator == instead of =. Each of the 3 sub-statements within the parentheses of your if statement should represent a boolean. In Java, = is used to assign a value and == is used to check equality. Therefore, you must change your if statement to: Also, rather than incrementing … Read more
Doing debugging is best done with a debugger, NetBeans (what you seem to be using if I look at other questions you have asked) has one. Just click in the left margin of an editor window to set a breakpoint and run the debugger. Program execution will stop at the breakpoint and you can have … Read more
Assuming your array is {10,20,30,40,50,60,70,80,90,100} What your loop does is: Iteration 1: array[1] = array[0]; {10,10,30,40,50,60,70,80,90,100} Iteration 2: array[2] = array[1]; {10,10,10,40,50,60,70,80,90,100} What you should be doing is
You have this error because you are trying to create an instance of abstract class, which is impossible. You have to or