Create new object using reflection?

Question

Given class Value :

public class Value {      private int xVal1;     private int xVal2;      private double pVal;       // constructor of the Value class       public Value(int _xVal1 ,int _xVal2 , double _pVal)     {         this.xVal1 = _xVal1;         this.xVal2 = _xVal2;         this.pVal = _pVal;     }      public int getX1val()     {         return this.xVal1;     }   ... } 

I'm trying to create a new instance of that class using reflection :

from Main :

    .... // some code      ....     ....     int _xval1 = Integer.parseInt(getCharacterDataFromElement(line));     int _xval2 = Integer.parseInt(getCharacterDataFromElement(line2));     double _pval = Double.parseDouble(getCharacterDataFromElement(line3));       Class c = null;      c = Class.forName("Value");      Object o = c.newInstance(_xval1,_xval2,_pval);  ... 

This doesn't work , Eclipse's output : The method newInstance() in the type Class is not applicable for the arguments (int, int, double)

If so , how can I create a new Value object using reflection , where I invoke the Constructor of Value ?

Thanks

Answer 1

You need to locate the exact constructor for this. Class.newInstance() can only be used to call the nullary constructor. So write

final Value v = Value.class.getConstructor(    int.class, int.class, double.class).newInstance(_xval1,_xval2,_pval); 

Answer 2

The Class.newInstance() method can only invoke a no-arg constructor. If you want to create objects using reflection with parameterized constructor than you need to use Constructor.newInstance(). You can simply write

Constructor<Value> constructor = Value.class.getConstructor(int.class, int.class, double.class); Value obj = constructor.newInstance(_xval1,_xval2,_pval); 

For details you can read Creating objects through Reflection in Java with Example