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Thread: how do you know what parameters go inside the parentheses when creating a new object?

  1. #1
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    Default how do you know what parameters go inside the parentheses when creating a new object?

    i am beginning to learn programming and started java.
    so sometimes i see codes like:


      Shape ball= new Shape();.// takes no parameter
        Shape ball= new Shape(1,2); //takes parameter

    So if there's like more than one constructor(or methods) in the subclass, how do you know which parameters to take?


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    Default Re: how do you know what parameters go inside the parentheses when creating a new object?

    Do you mean how does the programmer/user know which overloaded function to call, or how does the compiler know which function to call?

    The programmer/user knows by either reading the documentation, or by reading the source code.

    The compiler "knows" iff (if and only if) the type of the parameters can be unambiguously matched with one of the overloads. Note that the return type is not included in this calculation! So in your example:

    Shape ball = new Shape(); // will call Shape's constructor with no arguments.
    Shape ball = new Shape(1, 2); // will try to call new Shape(int, int) first, if it doesn't exists look for a function which ints can be implicitly casted to.

  3. The Following User Says Thank You to helloworld922 For This Useful Post:

    bango (July 19th, 2013)

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    Default Re: how do you know what parameters go inside the parentheses when creating a new object?

    Yeah I figured it out after I learnt about constructor overloading. Thank you

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