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When to use Comparable and Comparator
...clear how a comparable would sort, or do you have to resort to reading the javadoc? If it is the latter, odds are every future sorting use case would require a comparator, at which point the implementation of comparable may slow down users of the class, not speed them up.
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Jackson and generic type reference
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This is a well-known problem with Java type erasure: T is just a type variable, and you must indicate actual class, usually as Class argument. Without such information, best that can be done is to use bounds; and plain T is roughly same as 'T extends Object'....
When to use StringBuilder in Java [duplicate]
... generally preferable to use a StringBuilder for string concatenation in Java. Is this always the case?
9 Answers
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java : convert float to String and String to float
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Using Java’s Float class.
float f = Float.parseFloat("25");
String s = Float.toString(25.0f);
To compare it's always better to convert the string to float and compare as two floats. This is because for one float number there a...
Does Java have a HashMap with reverse lookup?
...ame for this type of data structure, and is anything like this included in Java's standard libraries? (or maybe Apache Commons?)
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How to convert a Map to List in Java?
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Using the Java 8 Streams API.
List<Value> values = map.values().stream().collect(Collectors.toList());
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Is null check needed before calling instanceof?
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The expression x instanceof SomeClass is false if x is null.
From the Java Language Specification, section 15.20.2, "Type comparison operator instanceof":
"At run time, the result of the
instanceof operator is true if the
value of the RelationalExpression is
not null and the referenc...
Sprintf equivalent in Java
Printf got added to Java with the 1.5 release but I can't seem to find how to send the output to a string rather than a file (which is what sprintf does in C). Does anyone know how to do this?
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Does JavaScript have the interface type (such as Java's 'interface')?
I'm learning how to make OOP with JavaScript . Does it have the interface concept (such as Java's interface )?
13 Answer...
What's the (hidden) cost of Scala's lazy val?
...he scala mailing list and gives implementation details of lazy in terms of Java code (rather than bytecode):
class LazyTest {
lazy val msg = "Lazy"
}
is compiled to something equivalent to the following Java code:
class LazyTest {
public int bitmap$0;
private String msg;
public String m...