Given that String s has been declared, the following 5 lines of code produce the same result:
int i = Integer.valueOf(s);
int y = Integer.parseInt(s);
int j = Integer.valueOf(s).intValue();
Integer x = Integer.valueOf(s);
Integer k = Integer.valueOf(s).intValue();
Are there circumstances where each one would be the preferred code? It appears that int and Integer are interchangeable and that .intValue() is not needed.
If you require an int, use parseInt(), if you require an Integer use valueOf(). Although they're (sort of) interchangeable now, it still makes more sense to use the one that directly returns the data type that you require. (Historically, they weren't interchangeable at all, this was introduced with auto-boxing and unboxing in Java 5.)
The intValue() method you're using is just converting the Integer class type to the int primitive, so using that and valueOf() is the worst possible combination, you never want to use that. (Nothing bad will happen, it's just longer to read, performs slightly worse and is generally more superfluous.)
If you don't care or don't know, then I'd use parseInt(). Especially as a beginner, it's more common that you want the primitive type rather than the class type.
int and Integer are made to look interchangeable by the magic of auto-boxing and auto-unboxing: In many cases where you need one but have the other, the compiler automagically inserts the necessary code to convert them.
This is useful, but if you know about it, you can avoid it in many places which results in slightly faster code (because there's less conversion to do).
Integer.parseInt() returns an int, so you should use it if you need an int
Integer.valueOf() returns an Integer, so you should use it if you need an Integer
Integer.valueOf().intValue() first creates an Integer and then extracts the int value from it. There's no good reason to use this instead of a simple Integer.parseInt().
The decision between int and Integer is easy to do as well:
generally you'd want to use the primitive type (int), if possible
if you need an Object (for example, if you want to put your number in a Collection), then you need to use the wrapper type (Integer), as the primitive type can't be used here.
int and Integer are not interchangeable.Because of Autoboxing feature fron java 5 onwards, int to Integer conversion is taken care by jvm itself.But we should not use Integer class unnecessarily.Primitive data types are always faster.Wrapper classes should be used only required.
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What is the difference between an int and an Integer in Java and C#?
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I have seen many times in code that people use int or Integer to declare variable in beans. I know int is datatype and Integer is wrapper class.
My question is, in which condition int or Integer should be used and is there any advantage of either of them over another?
My question is, in which condition int or Integer should be used and is there any advantage of either of them over another?
Well, you should use the reference type Integer whenever you have to. Integer is nothing more than a boxed int. An Object with a single field containing the specified int value.
Consider this example
public class Ex {
int field1;
Integer field2;
public Ex(){}
}
In this case field1 will be initialized with the value 0 while field2 will be initialized with null. Depending on what the fields represent, both approaches might be advantageous. If field1 represents some kind of UUID, would you want it to be initialized with a zero value?
I wouldn't worry too much about the performance implications of Autoboxing. You can still optimize after you get your code running.
For more information take a look at the documentation
https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/lang/Integer.html
You always use int, pretty much.
Integer should rarely be used; it is an intermediate type that the compiler takes care of for you. The one place where Integer is likely to appear is in generics, as int is simply not legal there. Here is an example:
List<Integer> indices = new ArrayList<Integer>();
int v = 10;
indices.add(v);
The above works: It compiles with no errors and does what you think it would (it adds '10' to a list of integer values).
Note that v is of type int, not Integer. That's the correct usage; you could write Integer here and the code works as well, but it wouldn't be particularly idiomatic java. Integer has no advantages over int, only disadvantages; the only time you'd use it, is if int is straight up illegal. Which is why I wrote List<Integer> and not List<int> as the latter is not legal java code (yet - give it a few versions and it may well be legal then, see Project Valhalla).
Note also that the compiler is silently converting your v here; if you look at the compiled code it is as if javac compiled indices.add(Integer.valueOf(v)) here. But that's fine, let the compiler do its thing. As a rule what the compiler emits and what hotspot optimizes are aligned; trust that what javac emits will be relatively efficient given the situation.
int is a primitive type, a value type for number literals.
it is used whenever and wherever you just want to do some basic arithmetical operation;
it is a value type, so it's stored in the Stack area of the memory, hence operations on it are much faster;
whenever it's needed, compiler implicitly and automatically casts back and forth (a.k.a Boxing and Unboxing) from int to Integer and vice versa;
Integer is a Class, which is a reference type and you instantiate an Object of that type.
you create an object of that class, which means, that you also have some methods and operations on that object;
any time you do some arithmetic operation on the instance of Integer, under the hood, it's still implemented by int primitives, and it's just wrapped into box/container;
it is a reference type / object, which is very important, as you can Serialize or Deserialize it;
it also has some very useful utility factory methods, like Integer.valueOf(..) for example, to parse the String as an integer;
it can be well used into declarations of the generic types and it, as a class, supports the hierarchy as well. For instance, it extends Number, and you can make use of this;
it is stored in the Heap area of the memory.
int is a primitive and Integer is an object .
From an memory footprint point of view , primitive consume less memory than object and also primitives are immutable (since they use pass by value ) .
Here is a good article on when to use what :
https://www.baeldung.com/java-primitives-vs-objects
In java if Integer can be used instead of int and Integer providing extra features then my question is why is int not being deprecated, and why int primitive type so extensively used?
One simple reason why it is not deprecated is that int is faster. And although you can use both but Integer is a better option(some may disagree as Integer introduces an extra overhead of boxing and unboxing), as it can handle null. int null will become 0.
From the docs:
However, very different things are going on under the covers here. An
int is a number; an > Integer is a pointer that can reference an
object that contains a number.
...
An int is not an object and cannot passed to any method that requires
objects. A common case is in using the provided collection classes (
List , Map , Set ) - though it is possible to write versions of these
classes that provide similar capabilities to the object versions. The
wrapper classes ( Integer , Double , etc) are frequently required
whenever introspection is used (such as in the reflection API).
EDIT:- The Joshua Bloch's reason is also good:
// Hideously slow program! Can you spot the object creation? public static void main(String[] args) {
Long sum = 0L;
for (long i = 0; i < Integer.MAX_VALUE; i++) {
sum += i;
}
System.out.println(sum); }
This program gets the right answer, but it is much slower than it should be, due to a one-character
typographical error. The variable sum is declared as a Long instead of
a long, which means that the program constructs about 2^31 unnecessary
Long instances (roughly one for each time the long i is added to the
Long sum). Changing the declaration of sum from Long to long reduces
the runtime from 43 seconds to 6.8 seconds on my machine.
Also check this int versus Integer
Boxed types have poorer performance and require more memory, Primitives are faster. And to avoid creating unnecessary objects.
Integer is an immutable type, once you created, you can't change it, taking much memory and high overhear compare to int
An int is a number; an Integer is a pointer that can reference an
object that contains a number.
int is a primitive type. If not set, the default value assigned is 0. Integer is an object which may contain an int. If the Integer object is not set, the default value is null
If you can use int do so. If the value can be null or is used as an Object e.g. Generics, use Integer
An int is a set construct. For example, only one "int 10" exists and is immutable. Integers on the other hand are full classes that contain an int field among others, have many more methods and are mutible.
int for speed and Integer for versatility.
if you have an method with int as argument, you do not have to nullcheck because it is a primitve type.
I am confused as to why Integer and int can be used interchangeably in Java even though one is a primitive type and the other is an object?
For example:
Integer b = 42;
int a = b;
Or
int d = 12;
Integer c = d;
The first few sentences of the posted article describe it pretty well:
You can’t put an int (or other primitive value) into a collection. Collections can only hold object references, so you have to box primitive values into the appropriate wrapper class (which is Integer in the case of int). When you take the object out of the collection, you get the Integer that you put in; if you need an int, you must unbox the Integer using the intValue method. All of this boxing and unboxing is a pain, and clutters up your code. The autoboxing and unboxing feature automates the process, eliminating the pain and the clutter.
That is basically it in a nutshell. It allows you take advantage of the Collections Framework for primatives without having to do the work yourself.
The primary disadvantage is that it confuses new programmers, and can lead to messy/confusing code if it's not understood and used correctly.
Java supports autoboxing and automatically wraps primitive values into objects and unwraps objects to primitive values for certain types, like char - Character, int - Integer, double - Double, etc.
Note from Oracle Documentation:
So when should you use autoboxing and unboxing? Use them only when there is an “impedance mismatch” between reference types and primitives, for example, when you have to put numerical values into a collection. It is not appropriate to use autoboxing and unboxing for scientific computing, or other performance-sensitive numerical code. An Integer is not a substitute for an int; autoboxing and unboxing blur the distinction between primitive types and reference types, but they do not eliminate it.
Because of autoboxing and autounboxing http://download.oracle.com/javase/1.5.0/docs/guide/language/autoboxing.html
Using an int and an Integer "interchangeably" is called autoboxing. This feature was introduced in Java 5. Before that, your example code wouldn't have compiled. Instead, you would have to write something like this:
Integer b = Integer.valueOf(42); // or new Integer(42);
int a = b.intValue();
or
int d = 12;
Integer c = Integer.valueOf(d); // or new Integer(d);
That's fairly verbose, which is why autoboxing was introduced. It's a bit of compiler magic to make life easier for the coder.
Technically, int and Integer themselves are not interchangeable and one cannot be used where the other is required. However, autoboxing allows implicit conversion between the two.
As a side note, there is one case where autoboxing (specifically unboxing) fails. If your code tries to autounbox a null value, you will get a NullPointerException at runtime, e.g.:
Integer b = null;
int a = b; // NullPointerException here!
Just something to be aware of...
It's called AutoBoxing. That will explain exactly what it is.
In addition to other answers, because Integer is a wrapper class, that lets you box and unbox an int value. Other info here.
The java language specification states that the java virtual machine must perform automatic boxing/unboxing for integers and a few other types.
Since Java 5, we've had boxing/unboxing of primitive types so that int is wrapped to be java.lang.Integer, and so and and so forth.
I see a lot of new Java projects lately (that definitely require a JRE of at least version 5, if not 6) that are using int rather than java.lang.Integer, though it's much more convenient to use the latter, as it has a few helper methods for converting to long values et al.
Why do some still use primitive types in Java? Is there any tangible benefit?
In Joshua Bloch's Effective Java, Item 5: "Avoid creating unnecessary objects", he posts the following code example:
public static void main(String[] args) {
Long sum = 0L; // uses Long, not long
for (long i = 0; i <= Integer.MAX_VALUE; i++) {
sum += i;
}
System.out.println(sum);
}
and it takes 43 seconds to run. Taking the Long into the primitive brings it down to 6.8 seconds... If that's any indication why we use primitives.
The lack of native value equality is also a concern (.equals() is fairly verbose compared to ==)
for biziclop:
class Biziclop {
public static void main(String[] args) {
System.out.println(new Integer(5) == new Integer(5));
System.out.println(new Integer(500) == new Integer(500));
System.out.println(Integer.valueOf(5) == Integer.valueOf(5));
System.out.println(Integer.valueOf(500) == Integer.valueOf(500));
}
}
Results in:
false
false
true
false
EDIT Why does (3) return true and (4) return false?
Because they are two different objects. The 256 integers closest to zero [-128; 127] are cached by the JVM, so they return the same object for those. Beyond that range, though, they aren't cached, so a new object is created. To make things more complicated, the JLS demands that at least 256 flyweights be cached. JVM implementers may add more if they desire, meaning this could run on a system where the nearest 1024 are cached and all of them return true... #awkward
Autounboxing can lead to hard to spot NPEs
Integer in = null;
...
...
int i = in; // NPE at runtime
In most situations the null assignment to in is a lot less obvious than above.
Boxed types have poorer performance and require more memory.
Primitive types:
int x = 1000;
int y = 1000;
Now evaluate:
x == y
It's true. Hardly surprising. Now try the boxed types:
Integer x = 1000;
Integer y = 1000;
Now evaluate:
x == y
It's false. Probably. Depends on the runtime. Is that reason enough?
Besides performance and memory issues, I'd like to come up with another issue: The List interface would be broken without int.
The problem is the overloaded remove() method (remove(int) vs. remove(Object)). remove(Integer) would always resolve to calling the latter, so you could not remove an element by index.
On the other hand, there is a pitfall when trying to add and remove an int:
final int i = 42;
final List<Integer> list = new ArrayList<Integer>();
list.add(i); // add(Object)
list.remove(i); // remove(int) - Ouch!
Can you really imagine a
for (int i=0; i<10000; i++) {
do something
}
loop with java.lang.Integer instead? A java.lang.Integer is immutable, so each increment round the loop would create a new java object on the heap, rather than just increment the int on the stack with a single JVM instruction. The performance would be diabolical.
I would really disagree that it's much mode convenient to use java.lang.Integer than int. On the contrary. Autoboxing means that you can use int where you would otherwise be forced to use Integer, and the java compiler takes care of inserting the code to create the new Integer object for you. Autoboxing is all about allowing you to use an int where an Integer is expected, with the compiler inserting the relevant object construction. It in no way removes or reduces the need for the int in the first place. With autoboxing you get the best of both worlds. You get an Integer created for you automatically when you need a heap based java object, and you get the speed and efficiency of an int when you are just doing arithmetic and local calculations.
Primitive types are much faster:
int i;
i++;
Integer (all Numbers and also a String) is an immutable type: once created it can not be changed. If i was Integer, than i++ would create a new Integer object - much more expensive in terms of memory and processor.
First and foremost, habit. If you've coded in Java for eight years, you accumulate a considerable amount of inertia. Why change if there is no compelling reason to do so? It's not as if using boxed primitives comes with any extra advantages.
The other reason is to assert that null is not a valid option. It would be pointless and misleading to declare the sum of two numbers or a loop variable as Integer.
There's the performance aspect of it too, while the performance difference isn't critical in many cases (though when it is, it's pretty bad), nobody likes to write code that could be written just as easily in a faster way we're already used to.
By the way, Smalltalk has only objects (no primitives), and yet they had optimized their small integers (using not all 32 bits, only 27 or such) to not allocate any heap space, but simply use a special bit pattern. Also other common objects (true, false, null) had special bit patterns here.
So, at least on 64-bit JVMs (with a 64 bit pointer namespace) it should be possible to not have any objects of Integer, Character, Byte, Short, Boolean, Float (and small Long) at all (apart from these created by explicit new ...()), only special bit patterns, which could be manipulated by the normal operators quite efficiently.
I can't believe no one has mentioned what I think is the most important reason:
"int" is so, so much easier to type than "Integer". I think people underestimate the importance of a concise syntax. Performance isn't really a reason to avoid them because most of the time when one is using numbers is in loop indexes, and incrementing and comparing those costs nothing in any non-trivial loop (whether you're using int or Integer).
The other given reason was that you can get NPEs but that's extremely easy to avoid with boxed types (and it is guaranteed to be avoided as long as you always initialize them to non-null values).
The other reason was that (new Long(1000))==(new Long(1000)) is false, but that's just another way of saying that ".equals" has no syntactic support for boxed types (unlike the operators <, >, =, etc), so we come back to the "simpler syntax" reason.
I think Steve Yegge's non-primitive loop example illustrates my point very well:
http://sites.google.com/site/steveyegge2/language-trickery-and-ejb
Think about this: how often do you use function types in languages that have good syntax for them (like any functional language, python, ruby, and even C) compared to java where you have to simulate them using interfaces such as Runnable and Callable and nameless classes.
Couple of reasons not to get rid of primitives:
Backwards compatability.
If it's eliminated, any old programs wouldn't even run.
JVM rewrite.
The entire JVM would have to be rewritten to support this new thing.
Larger memory footprint.
You'd need to store the value and the reference, which uses more memory. If you have a huge array of bytes, using byte's is significantly smaller than using Byte's.
Null pointer issues.
Declaring int i then doing stuff with i would result in no issues, but declaring Integer i and then doing the same would result in an NPE.
Equality issues.
Consider this code:
Integer i1 = 5;
Integer i2 = 5;
i1 == i2; // Currently would be false.
Would be false. Operators would have to be overloaded, and that would result in a major rewrite of stuff.
Slow
Object wrappers are significantly slower than their primitive counterparts.
Objects are much more heavyweight than primitive types, so primitive types are much more efficient than instances of wrapper classes.
Primitive types are very simple: for example an int is 32 bits and takes up exactly 32 bits in memory, and can be manipulated directly. An Integer object is a complete object, which (like any object) has to be stored on the heap, and can only be accessed via a reference (pointer) to it. It most likely also takes up more than 32 bits (4 bytes) of memory.
That said, the fact that Java has a distinction between primitive and non-primitive types is also a sign of age of the Java programming language. Newer programming languages don't have this distinction; the compiler of such a language is smart enough to figure out by itself if you're using simple values or more complex objects.
For example, in Scala there are no primitive types; there is a class Int for integers, and an Int is a real object (that you can methods on etc.). When the compiler compiles your code, it uses primitive ints behind the scenes, so using an Int is just as efficient as using a primitive int in Java.
In addition to what others have said, primitive local variables are not allocated from the heap, but instead on the stack. But objects are allocated from the heap and thus have to be garbage collected.
It's hard to know what kind of optimizations are going on under the covers.
For local use, when the compiler has enough information to make optimizations excluding the possibility of the null value, I expect the performance to be the same or similar.
However, arrays of primitives are apparently very different from collections of boxed primitives. This makes sense given that very few optimizations are possible deep within a collection.
Furthermore, Integer has a much higher logical overhead as compared with int: now you have to worry about about whether or not int a = b + c; throws an exception.
I'd use the primitives as much as possible and rely on the factory methods and autoboxing to give me the more semantically powerful boxed types when they are needed.
int loops = 100000000;
long start = System.currentTimeMillis();
for (Long l = new Long(0); l<loops;l++) {
//System.out.println("Long: "+l);
}
System.out.println("Milliseconds taken to loop '"+loops+"' times around Long: "+ (System.currentTimeMillis()- start));
start = System.currentTimeMillis();
for (long l = 0; l<loops;l++) {
//System.out.println("long: "+l);
}
System.out.println("Milliseconds taken to loop '"+loops+"' times around long: "+ (System.currentTimeMillis()- start));
Milliseconds taken to loop '100000000' times around Long: 468
Milliseconds taken to loop '100000000' times around long: 31
On a side note, I wouldn't mind seeing something like this find it's way into Java.
Integer loop1 = new Integer(0);
for (loop1.lessThan(1000)) {
...
}
Where the for loop automatically increments loop1 from 0 to 1000
or
Integer loop1 = new Integer(1000);
for (loop1.greaterThan(0)) {
...
}
Where the for loop automatically decrements loop1 1000 to 0.
Primitive types have many advantages:
Simpler code to write
Performance is better since you are not instantiating an object for the variable
Since they do not represent a reference to an object there is no need to check for nulls
Use primitive types unless you need to take advantage of the boxing features.
You need primitives for doing mathematical operations
Primitives takes less memory as answered above and better performing
You should ask why Class/Object type is required
Reason for having Object type is to make our life easier when we deal with Collections. Primitives cannot be added directly to List/Map rather you need to write a wrapper class. Readymade Integer kind of Classes helps you here plus it has many utility methods like Integer.pareseInt(str)
I agree with previous answers, using primitives wrapper objects can be expensive.
But, if performance is not critical in your application, you avoid overflows when using objects. For example:
long bigNumber = Integer.MAX_VALUE + 2;
The value of bigNumber is -2147483647, and you would expect it to be 2147483649. It's a bug in the code that would be fixed by doing:
long bigNumber = Integer.MAX_VALUE + 2l; // note that '2' is a long now (it is '2L').
And bigNumber would be 2147483649. These kind of bugs sometimes are easy to be missed and can lead to unknown behavior or vulnerabilities (see CWE-190).
If you use wrapper objects, the equivalent code won't compile.
Long bigNumber = Integer.MAX_VALUE + 2; // Not compiling
So it's easier to stop these kind of issues by using primitives wrapper objects.
Your question is so answered already, that I reply just to add a little bit more information not mentioned before.
Because JAVA performs all mathematical operations in primitive types. Consider this example:
public static int sumEven(List<Integer> li) {
int sum = 0;
for (Integer i: li)
if (i % 2 == 0)
sum += i;
return sum;
}
Here, reminder and unary plus operations can not be applied on Integer(Reference) type, compiler performs unboxing and do the operations.
So, make sure how many autoboxing and unboxing operations happen in java program. Since, It takes time to perform this operations.
Generally, it is better to keep arguments of type Reference and result of primitive type.
The primitive types are much faster and require much less memory. Therefore, we might want to prefer using them.
On the other hand, current Java language specification doesn’t allow usage of primitive types in the parameterized types (generics), in the Java collections or the Reflection API.
When our application needs collections with a big number of elements, we should consider using arrays with as more “economical” type as possible.
*For detailed info see the source: https://www.baeldung.com/java-primitives-vs-objects
To be brief: primitive types are faster and require less memory than boxed ones
in wrapper classes we have two types of methods parseXxx() and valueOf() in every wrapper class for interconversion between primitive and wrapper objects.recently java 1.5 introduced auto boxing and boxing.so why they didn't deprecate those methods.
Because Autoboxing and Auto Unboxing are just compile time features. Try writing something like this in your source file and then have a look at the decompiled code:
Integer i = 10;
Decompiled code:
Integer i = Integer.valueOf(10);
Similarly,
int i = new Integer(100);
will give you the below when decompiled:
int i = (new Integer(100)).intValue();
Thus, the JVM still heavily relies on these methods at runtime, though it's masked when you write the code.
Well, parseXxx() is entirely unlike boxing; it turns a String into a primitive object. valueOf(), on the other hand, is actually used in boxing -- it either constructs a new wrapper object, or it fetches an existing one from a cache, depending on the value. The Java compiler generates a call to valueOf(), and that's precisely what boxing means.
1. There can be value sometimes in explicitly stating some conversion (for the clarity of e.g. some unobvious/obscure case).
2. Wouldn't that deprecation result in old programs becoming excessively littered with deprecation warnings?
As the command line arguments are treated as String Array, but given the condition when you are expecting command line argument other than String datatype(that may be primitives) i.e. boolean, int, byte, short, long, float, double, char than you need to parse the argument into the one what your program expects and here you use parseXXX() methods, to be precise parseXXX method take String argument and return the appropriate data type which you are trying to parse into.