Copy Constructor in Java

Reference:tutorialpoints, Geekforgeeks

The copy constructor is a constructor which creates an object by initializing it with an object of the same class , which has been created previously. The copy constructor is used to:

• Initialize one object from another of the same type.

• Copy an object to pass it as an argument to a function.

• Copy an object to return it from a function.

In C + +, if a copy constructor is not defined in a class, the compiler itself defines one.

Java also supports copy constructor. But, unlike C + +, Java doesn ' t create a default copy constructor if you don ' t write your own.

1 classComplex {2  3     Private DoubleRe, im;4      5     //A normal parametrized constructor6      PublicComplex (DoubleReDoubleim) {7          This. Re =re;8          This. im =im;9     }Ten       One     //copy Constructor A Complex (Complex c) { -System.out.println ("Copy constructor called"); -Re =c.re; theim =c.im; -     } -        -     //overriding the toString of Object class + @Override -      PublicString toString () { +         return"(" + Re + "+" + im + "i)"; A     } at } -   -  Public classMain { -   -      Public Static voidMain (string[] args) { -Complex C1 =NewComplex (10, 15); in           -         //following involves a copy constructor call toComplex C2 =NewComplex (C1);  +   -         //Note that following doesn ' t involve a copy constructor call as the         //non-primitive variables is just references. *Complex C3 =C2;  $  Panax NotoginsengSystem.out.println (C2);//toString () of C2 is called here -     } the}

Output:

Copy Constructor

Called (10.0 + 15.0i)

1 classComplex {2  3     Private DoubleRe, im;4  5      PublicComplex (DoubleReDoubleim) {6          This. Re =re;7          This. im =im;8     }9 }Ten   One  Public classMain { A       -      Public Static voidMain (string[] args) { -Complex C1 =NewComplex (10, 15);  theComplex C2 =NewComplex (C1);//Compiler Error here -     } -}

Compile Error

Copy Constructor in Java