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Why does writeObject throw java.io.NotSerializableException and how do I fix it?
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java.io.NotSerializableException can occur when you serialize an inner class instance because:
serializing such an inner class instance will result in serialization
of its associated outer class instance as well
Serializatio...
What is the “N+1 selects problem” in ORM (Object-Relational Mapping)?
...2.
Most ORM tools give you several ways to prevent N+1 selects.
Reference: Java Persistence with Hibernate, chapter 13.
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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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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'....
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...
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...
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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Any way to declare a size/partial border to a box?
...raw some of the borders.
See here.
Code:
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Responsive partial borders</title>
<style>
/* ungrid without mobile */
.row{width:100%;display:table;table-layout:fi...
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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