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How can I count occurrences with groupBy?
...h each group... and then Collectors.counting() to do the counting:
import java.util.*;
import java.util.stream.*;
class Test {
public static void main(String[] args) {
List<String> list = new ArrayList<>();
list.add("Hello");
list.add("Hello");
list...
R: += (plus equals) and ++ (plus plus) equivalent from c++/c#/java, etc.?
Does R have a concept of += (plus equals) or ++ (plus plus) as c++/c#/others do?
8 Answers
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What does “var FOO = FOO || {}” (assign a variable or an empty object to that variable) mean in Java
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i like to say it's the #ifndef/#define for javascript :)
– Darren Kopp
Jun 22 '11 at 17:15
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Simplest way to serve static data from outside the application server in a Java web application
I have a Java web application running on Tomcat. I want to load static images that will be shown both on the Web UI and in PDF files generated by the application. Also new images will be added and saved by uploading via the Web UI.
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Missing return statement in a non-void method compiles
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The Java compiler is smart enough to find the unreachable code ( the code after while loop)
and since its unreachable, there is no point in adding a return statement there (after while ends)
same goes with conditional if
publi...
Difference between matches() and find() in Java Regex
... {
Pattern p = Pattern.compile("\\d");
String candidate = "Java123";
Matcher m = p.matcher(candidate);
if (m != null){
System.out.println(m.find());//true
System.out.println(m.matches());//false
}
}
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Converting BigDecimal to Integer
...red Oct 28 '10 at 14:01
willcodejavaforfoodwillcodejavaforfood
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Check if a value exists in ArrayList
... HashSet than an ArrayList when you are checking for existence of a value.
Java docs for HashSet says: "This class offers constant time performance for the basic operations (add, remove, contains and size)"
ArrayList.contains() might have to iterate the whole list to find the instance you are looki...
Sorting arraylist in alphabetical order (case insensitive)
... return s1.compareToIgnoreCase(s2);
}
});
Or if you are using Java 8:
list.sort(String::compareToIgnoreCase);
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When would you use a WeakHashMap or a WeakReference?
... Article now at web.archive.org/web/20061130103858/http://weblogs.java.net/blog/…
– mjn42
Jan 30 '19 at 8:38
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