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What is the advantage of using abstract classes instead of traits?
... have constructor parameters
Abstract classes are fully interoperable with Java. You can call them from Java code without any wrappers. Traits are fully interoperable only if they do not contain any implementation code
shar...
InputStream from a URL
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Use java.net.URL#openStream() with a proper URL (including the protocol!). E.g.
InputStream input = new URL("http://www.somewebsite.com/a.txt").openStream();
// ...
See also:
Using java.net.URLConnection to fire and handle H...
Is there a Java equivalent or methodology for the typedef keyword in C++?
...redibly helpful. Do you know of a way to achieve similar functionality in Java, whether that be a Java mechanism, pattern, or some other effective way you have used?
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what's the correct way to send a file from REST web service to client?
...ts that I don't know where I should even begin. My REST service is made on Java and I'm using Jersey, I'm sending all the data using the JSON format.
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Can a java file have more than one class?
What is the purpose of having more than one class in a Java file ? I am new to Java.
18 Answers
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Java List.contains(Object with field value equal to x)
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Streams
If you are using Java 8, perhaps you could try something like this:
public boolean containsName(final List<MyObject> list, final String name){
return list.stream().filter(o -> o.getName().equals(name)).findFirst().isPresent();
}...
Best way to encode text data for XML in Java?
Very similar to this question , except for Java.
21 Answers
21
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Why is 128==128 false but 127==127 is true when comparing Integer wrappers in Java?
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When you compile a number literal in Java and assign it to a Integer (capital I) the compiler emits:
Integer b2 =Integer.valueOf(127)
This line of code is also generated when you use autoboxing.
valueOf is implemented such that certain numbers are "pooled", ...
Strings are objects in Java, so why don't we use 'new' to create them?
...ring literals [ie, Strings like "abcd" but not like new String("abcd")] in Java are interned - this means that every time you refer to "abcd", you get a reference to a single String instance, rather than a new one each time. So you will have:
String a = "abcd";
String b = "abcd";
a == b; //True
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At runtime, find all classes in a Java application that extend a base class
...n, InstantiationException {
Reflections reflections = new Reflections("java.util");
Set<Class<? extends List>> classes = reflections.getSubTypesOf(java.util.List.class);
for (Class<? extends List> aClass : classes) {
System.out.println(aClass.getName());
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