Is it possible to instantiate objects without constructor in Java

Question

When learning about String literals vs String objects, I came across the fact that there are 2 possible ways to instantiate a variable of type String

//Using literals
String s1 = "text";

//Using constructor
String s2 = new String("text");

I was wondering if it is possible to somehow create an class and instead of instantiating it with a constructor, one could instantiate it using a literal

This is what I mean

class Value {
    int value;
    //Some methods
}

Value val = 10; //Program automatically sets val.value = 10

Java doesn't give you a way to do this. But even where you use literals for objects, constructors and other factory methods end up being invoked under the hood anyway. — ernest_k, Nov 13 '18 at 17:12
related: https://stackoverflow.com/questions/2009228/strings-are-objects-in-java-so-why-dont-we-use-new-to-create-them — Mark Rotteveel, Nov 13 '18 at 17:21

score 1 · Answer 1 · edited Nov 13 '18 at 17:59

1

No, this isn't possible. The closest thing that Java has to this is autoboxing, where you can write something like:

Integer val = 10;

and the compiler automatically turns that assignment into one involving the primitives cache (there is a fixed set of primitive values that are guaranteed cached: boolean true/false, byte and char values 0-127, and int values -128 to 127, As per the spec. Although a JVM may, and almost always does, have a more extensive primitives cache than that).

edited Nov 13 '18 at 17:59

Mike 'Pomax' Kamermans

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answered Nov 13 '18 at 17:13

Richard Fearn

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Nit: that assignment *won't* create a new instance. Owing to caching. – Andy Turner Nov 13 '18 at 17:14
@AndyTurner That's why I said "convert" ;-) – Richard Fearn Nov 13 '18 at 17:16

score 1 · Answer 2 · answered Nov 13 '18 at 17:15

1

No. Although you can write String s1 = "text";, the java compiler automatically creates an object. This may be the reason to misguide you. But it happens inside.

answered Nov 13 '18 at 17:15

dilanSachi

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score 1 · Answer 3 · answered Nov 13 '18 at 17:22

Most of the scenarios its not possible. Creating a String like you have and assigning a int value both are using constructors even we can't see it directly.

How ever there are rare scenarios like this. Please read this. Will be good to add to your knowledge :)

Is it possible to instantiate objects without constructor in Java

3 Answers3