DownCasting in Java

Downcasting is allowed when there is a possibility that it suceeds at run time:
Object o = getSomeObject(),
String s = (String) o; // this is allowed because o could reference a String

In some cases this will not succeed:
Object o = new Object();
String s = (String) o; // this will fail at runtime, because o doesn't reference a String

In others it will work:
Object o = "a String";
String s = (String) o; // this will work, since o references a String

Note that some casts will be disallowed at compile time, because they will never succeed at all:
Integer i = getSomeInteger();
String s = (String) i; // the compiler will not allow this, since i can never reference a String.

How to check downcasting is valid or not :
else if (getClass( ) != anObject.getClass())
     return false;

Good reference material is here :
http://www.programmerinterview.com/index.php/java-questions/downcasting-in-java/


Casting between primitive types (like int, float, and double) and

converting between objects and primitive types.

---------------------------------------------------------------------
---------------------------------------------------------------------

  I.  Converting int to float:

      //  The following lines of code WORK ......
  
      int   xInt = 120;
      float xFloat;

         xFloat = xInt;

---------------------------------------------------------------------
---------------------------------------------------------------------

 II.  Converting float to int:
---------------------------------------------------------------------

      //  The following lines of code DO NOT work! ......
  
      int   xInt;
      float xFloat = 3.8644f;

         xInt = xFloat;

      //    During compilation you will get the following ERROR:
      //    "Explicit cast needed to convert float to int."

---------------------------------------------------------------------

      //  The following lines of code WORK ......
  
      int   xInt;

         Float   x = new Float("3.8644");
         xInt      = x.intValue();

      //  Note that the value of xInt will be 3 (not 4) because
      //  the fractional part of the floating point number is
      //  truncated (not rounded) when converting float to int.

---------------------------------------------------------------------

      //  The following lines of code ALSO WORK ......
  
      int   xInt;
      float xFloat = 3.8644f;

         xInt = (int) xFloat;


---------------------------------------------------------------------
---------------------------------------------------------------------

III.  Converting double to float:
---------------------------------------------------------------------

      //  The following lines of code DO NOT work! ......
  
      double   xDouble = 3.8644951;
      float    xFloat;

         xFloat = xDouble;

      //    During compilation you will get the following ERROR:
      //    "Explicit cast needed to convert double to float."

---------------------------------------------------------------------

      //  The following lines of code WORK ......
  
      float    xFloat;

         Double  x = new Double("3.8644951");
         xFloat    = x.floatValue();

---------------------------------------------------------------------

      //  The following lines of code ALSO WORK ......
  
      double   xDouble = 3.8644951;
      float     xFloat;

         xFloat = (float) xDouble;

---------------------------------------------------------------------

      //  Note, also, that the following lines of code DO NOT work! 
  
      float xFloat = 3.8644f;
      float sum;

         sum = 2.0 + xFloat;

      //  They will not work because, by default, in Java the
      //  2.0 on the right-hand-side of the last expression is a
      //  double-precision number, so "xFloat" is first converted
      //  to a double-precision number before it is added to "2.0",
      //  then right-hand-side is of type "double" while the left-
      //  hand-side is of type "float" so you have to perform an
      //  explicit type cast, like....

         sum = (float) (2.0 + xFloat);

      //  or ....

         sum = 2.0f + xFloat;

---------------------------------------------------------------------
---------------------------------------------------------------------

example :

int x = 3, y = 4;
  float z = x * y;
  System.out.println(z);//12.0
  float xF = 3, yF = 4;
  int mult = (int) (xF * yF);
  System.out.println(mult);//12