Why conversion of Wrapper Integer to Float is not possible in java

Question

Why Wrapper Float typing doesn't work in java for Wrapper Integer type.

public class Conversion { public static void main(String[] args) { Integer i = 234; Float b = (Float)i; System.out.println(b); } } 

Answer 1

An Integer not a Float . Casting will work with objects if Integer subclass of Float , but it is not.

Java will not automatically decompress Integer into int , drop it to Float , and then automatically to Float when the only code to run this desired behavior is a cast.

Interestingly, this works:

 Float b = (float)i; 

Java will be automatically-unbox i to int , then there will be an explicit cast to Float (a extension of the primitive conversion, JLS 5.1.2 ), then the assignment conversion automatically translates it to Float .

Answer 2

You ask him to do too much. You want it to unpack i, throw it in a float, and then insert it. The compiler cannot guess that unboxing I would help him. If, however, you replace (Float) cast (float) cast, it guesses what I will need to unpack to be great for float, and then happily automatically add it to Float.

Answer 3

Packers must “objectify” the associated primitive types. This type of casting is done at the “object level” to express it in some way, not the actual value of the wrapped primitive type.

Since there is no relationship between Float and Integer (they are associated with Number , but they are just siblings), casting cannot be done directly.

Answer 4

You can rewrite your class to work as you want:

 public class Conversion { public Float intToFloat(Integer i) { return (Float) i.floatValue(); } } 

Answer 5

 public class Conversion { public static void main(String[] args) { Integer i = 234; Float b = i.floatValue(); System.out.println(b); }}