Questions tagged [java]
Java is a high-level object-oriented programming language. Use this tag when you're having problems using or understanding the language itself. This tag is frequently used alongside other tags for libraries and/or frameworks used by Java developers.
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Why is processing a sorted array faster than processing an unsorted array?
In this C++ code, sorting the data (before the timed region) makes the primary loop ~6x faster:
#include <algorithm>
#include <ctime>
#include <iostream>
int main()
{
// ...
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Is Java "pass-by-reference" or "pass-by-value"?
I always thought Java uses pass-by-reference. However, I read a blog post which claims that Java uses pass-by-value. I don't think I understand the distinction the author is making.
What is the ...
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Why is subtracting these two epoch-milli Times (in year 1927) giving a strange result?
If I run the following program, which parses two date strings referencing times 1 second apart and compares them:
public static void main(String[] args) throws ParseException {
SimpleDateFormat sf ...
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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 have an InputStream that contains text data, and I want to convert it to a String, so for ...
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How do I avoid checking for nulls in Java?
I use x != null to avoid NullPointerException. Is there an alternative?
if (x != null) {
// ...
}
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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 applications?
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Create ArrayList from array
Element[] array = {new Element(1), new Element(2), new Element(3)};
How do I convert the above variable of type Element[] into a variable of type ArrayList<Element>?
ArrayList<Element> ...
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How do I generate random integers within a specific range in Java?
How do I generate a random int value in a specific range?
The following methods have bugs related to integer overflow:
randomNum = minimum + (int)(Math.random() * maximum);
// Bug: `randomNum` can be ...
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Proper use cases for Android UserManager.isUserAGoat()?
I was looking at the new APIs introduced in Android 4.2.
While looking at the UserManager class I came across the following method:
public boolean isUserAGoat()
Used to determine whether the ...
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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 within it, what is the most efficient way of going through the map?
Will the ordering of ...
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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:
int i = 5;
long j = 8;
Then i = i + j; will not compile but i += j; will compile fine.
...
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Why is char[] preferred over String for passwords?
In Swing, the password field has a getPassword() (returns char[]) method instead of the usual getText() (returns String) method. Similarly, I have come across a suggestion not to use String to handle ...
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Iterate through a HashMap [duplicate]
What's the best way to iterate over the items in a HashMap?
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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 dumb, having no idea how to start creating one.
What would an example be?
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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), public, protected and private, while making class and interface and dealing with ...
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