Unboxing Long in java

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In some code I see this:

private void compute(Long a, Long b, Long c) {
        long result = a-(b+c);
...

It seems a bit strange that the result is stored in a primitive long instead of a Long object corresponding to its operands.

Are there any reason that a result should be stored as a primitive?

Unboxing Long in java, It seems a bit strange that the result is stored in a primitive long instead of a Long object corresponding to its operands. No, what is "strange" is� The Java compiler applies unboxing when an object of a wrapper class is: Passed as a parameter to a method that expects a value of the corresponding primitive type. Assigned to a variable of the corresponding primitive type.

The reason is obvious: result is declared as primitive.

Autoboxing and Unboxing in Java, Unboxing: Converting an object of a wrapper type to its corresponding primitive value is called unboxing. For example conversion of Integer to int. The Java compiler applies unboxing when an object of a wrapper class is: Passed as a parameter to a method that expects a value of the corresponding primitive type. Converting an object of a wrapper type (Integer) to its corresponding primitive (int) value is called unboxing. The Java compiler applies unboxing when an object of a wrapper class is: Passed as a parameter to a method that expects a value of the corresponding primitive type. Assigned to a variable of the corresponding primitive type.

The arithmetic operators + and - are not defined for boxed types (e.g. Long) but for primitive types (e.g. long).

The result is also a long. See Autoboxing and Unboxing tutorial

Autoboxing this into a Long would result in a small performance cost. It is also unnecessary because

  1. We know it will be non-null (if a, b or c were null, a NullPointerException would occur).
  2. It would be autoboxed implicitly if we use it later where a Long is required.

Java Autoboxing and Unboxing with examples, Unboxing: It is just the reverse process of autoboxing. Automatically converting an object of a wrapper class to its corresponding primitive type is known as unboxing. For example – conversion of Integer to int, Long to long, Double to double etc. Podcast: We chat with Major League Hacking about all-nighters, cup stacking, and therapy dogs. Listen now..

Based on your needs.I mean the decelaration.

Autoboxing and unboxing can happen anywhere where an object is expected and primitive type is available

Autoboxing and Unboxing in Java, Java provides eight built-in names for primitive data types: byte, short, int, long, char, Boolean and double, according to the type of value they� Unboxing in Java is an automatic conversion of an object of a wrapper class to the value of its respective primitive data type by the compiler. It is the opposite technique of Autoboxing. For example converting Integer class to int datatype, converting Double class into double data type, etc. When Unboxing in Java occurs?

Usually you should prefer using primitives, especially if you are certain they cannot be null. If you insist on using the boxed types always think extra hard about what happens when it is null. Java will do the boxing and unboxing automatically for you, but staring at an int and wondering why you got a NullPointerException can be fun.

Java Performance Notes: Autoboxing / Unboxing, What would you think if I said "We can run the following code snippet 5 times faster after changing just 1 character"? long t = System. Introduction to Autoboxing and Unboxing in Java. Autoboxing is the automatic conversion that the Java compiler makes between the primitive types and their corresponding object wrapper classes, i.e. conversion from int to Integer, double to Double, etc. Unboxing is the automatic conversion from wrapper class objects to their equivalent primitives i.e. Integer to int etc.

In this article, we will discuss what is auto-boxing and unboxing with examples. Autoboxing is the automatic conversion that the Java compiler makes between the primitive types and their corresponding object wrapper classes. For example, converting an int to an Integer, a double to a Double, and so on. The reverse i.e Unwrapping the object into corresponding primitive data is called Unboxing.

In the java.lang package java provides a separate class for each of the primitive data type namely Byte, Character, Double, Integer, Float, Long, Short. Converting primitive datatype to object is called boxing. Example Integer obj = new Integer ("2526"); Whereas, converting an object into corresponding primitive datatype is known as unboxing. Example

Simple Example of Unboxing in java: The automatic conversion of wrapper class type into corresponding primitive type, is known as Unboxing. Let's see the example of unboxing: class UnboxingExample1 {. public static void main (String args []) {. Integer i=new Integer (50);

Comments
  • A more serious question is why Long has been used at all. It is far less efficient.
  • It is stored as a primitive because you have declared it as a primitive.
  • Perhaps you can find some clues here link
  • @dmiller2117 I suppose what he meant is that he is reading someone else's code and wondering, why this someone used the primitive type there.
  • It's also funny that a void method has a local variable called "result" ... but I guess it would mean something else :P
  • That's actually not the reason.
  • I don't see why this is not the reason. If under "result" you understand the declared variable, then this is the reason. If under "result" you understand the result of the operation "a-(b+c)", then the reason is that the addition operation is defined for primitives and this is why the Longs are auto-unboxed before being added.
  • Hey there, firstly your answer is not really an answer, as the mechanism you are explaining here (autoboxing & unboxing), converting Long objects to long primitives, could also convert the result to a Long object if it was Long result = a-(b+c);. Secondly and lastly, your post is poorly formatted, the 1/2/3 structure makes no sense at all.
  • Sure Sir if your claiming this as wrong then please enlighten me with Correct analysis. and more ever if Long result there then again there will be an auto-boxing step
  • I won't, because that's not why I was here. I am simply reviewing late answers. I'm just saying that your answer isn't helpful, as it is just saying the same stuffs as the answer by Michael Borgwardt, which was posted the same day as the question. But his is better formatted, explained / developed. If you want to help others, answer questions that needs to be, and care about the helpfulness and formatting of it.
  • Thank You for the reply .Sure Will take of your advise in future