56
votes
3
answers
1.8K
views
Why is printing "B" dramatically slower than printing "#"?
I generated two matrices of 1000 x 1000: First Matrix: O and #. Second Matrix: O and B. Using the following
59
votes
30
answers
1.1K
views
How do I test a private function or a class that has private methods, fields or inner classes?
How do I unit test (using xUnit) a class that has internal private methods, fields or nested classes? Or a fun
63
votes
30
answers
2.2K
views
Initialization of an ArrayList in one line
I wanted to create a list of options for testing purposes. At first, I did this: ArrayList<String> plac
52
votes
26
answers
716
views
What is a serialVersionUID and why should I use it?
Eclipse issues warnings when a serialVersionUID is missing. The serializable class Foo does not declare
52
votes
30
answers
2.6K
views
How do I convert a String to an int in Java?
How can I convert a String to an int in Java? My String contains only numbers, and I want to return the numbe
54
votes
30
answers
918
views
When to use LinkedList over ArrayList in Java?
I've always been one to simply use: List<String> names = new ArrayList<>(); I use the inte
57
votes
29
answers
2K
views
What is the difference between public, protected, package-private and private in Java?
In Java, are there clear rules on when to use each of access modifiers, namely the default (package private),
53
votes
30
answers
2.2K
views
How can I create a memory leak in Java?
I just had an interview where I was asked to create a memory leak with Java. Needless to say, I felt pretty du
67
votes
30
answers
829
views
How do I efficiently iterate over each entry in a Java Map?
If I have an object implementing the Map interface in Java and I wish to iterate over every pair contained wit
60
votes
18
answers
440
views
Why is char[] preferred over String for passwords?
In Swing, the password field has a getPassword() (returns char[]) method instead of the usual getText() (retur
64
votes
11
answers
978
views
Why don't Java's +=, -=, *=, /= compound assignment operators require casting?
Until today, I thought that for example: i += j; Was just a shortcut for: i = i + j; But if we try this:
55
votes
30
answers
2.2K
views
How do I generate random integers within a specific range in Java?
How do I generate a random int value in a specific range? I have tried the following, but those do not work: A
58
votes
11
answers
2.2K
views
60
votes
30
answers
340
views
Create ArrayList from array
I have an array that is initialized like: Element[] array = {new Element(1), new Element(2), new Element(3)};
60
votes
30
answers
2.4K
views
What are the differences between a HashMap and a Hashtable in Java?
What are the differences between a HashMap and a Hashtable in Java? Which is more efficient for non-threaded
50
votes
30
answers
2.6K
views
Avoiding NullPointerException in Java
I use object != null a lot to avoid NullPointerException. What is an alternative to: if (someobject != null) {
55
votes
30
answers
2K
views
How do I read / convert an InputStream into a String in Java?
If you have a java.io.InputStream object, how should you process that object and produce a String? Suppose I
52
votes
30
answers
2.2K
views
Is Java "pass-by-reference" or "pass-by-value"?
I always thought Java uses pass-by-reference. However, I've seen a blog post that claims that Java uses p
53
votes
10
answers
1.5K
views
Why is subtracting these two times (in 1927) giving a strange result?
If I run the following program, which parses two date strings referencing times 1 second apart and compares th
63
votes
27
answers
2.9K
views
Why is processing a sorted array faster than processing an unsorted array?
Here is a piece of C++ code that shows some very peculiar behavior. For some strange reason, sorting the data
