float error

[Sagarya Kulkarni]

Float a=new Float(9.0f);
float b=(float)9.0;
System.out.println(b.equals(a));

the output is
Demo.java:7: float cannot be dereferenced
System.out.println(b.equals(a));
^
1 error

WHAT IT MEANS?

[Seetharaman Venkatasamy]

float(b) is different from Float(a)

[Sagarya Kulkarni]

but what 'dereferenced' means?
if i use a.equals(b), it returns true. why is it so?

[Madhu Desai]

Sagarya Kulkarni wrote:Float a=new Float(9.0f);
float b=(float)9.0;
System.out.println(b.equals(a));

the output is
Demo.java:7: float cannot be dereferenced
System.out.println(b.equals(a));
^
1 error

WHAT IT MEANS?

.equals() is only used between objects. Not between primitive and Object.

if you want to check for equality, do the conversion before. like...

class Checks {
	public static void main (String[] args) {
		Float a = new Float(9.0f);
		float b = (float)9.0f;
		
		//1st Method: unwrap Float 'a' to primitive and compare
		System.out.println (b == (a.floatValue())); 
			
		//2nd Method: AutoBox(upgrade) 'b' to wrapper(object) Float
		System.out.println (a.equals(b));
    }
}    

[Seetharaman Venkatasamy]

Sagarya Kulkarni wrote:if i use a.equals(b), it returns true. why is it so?

Because a object has an equals()

[Vishwanath Krishnamurthi]

Sagarya Kulkarni wrote:but what 'dereferenced' means?
if i use a.equals(b), it returns true. why is it so?

a is an object. It has an equals method.
b is not an object. It is just a primitive and so you cannot call do anything like

Sagarya Kulkarni wrote: float b=(float)9.0;
System.out.println(b.equals(a));

Try changing the declaration

float b=(float)9.0;
to
Float b=(float)9.0;

[Jesper de Jong]

Sagarya Kulkarni wrote:but what 'dereferenced' means?
if i use a.equals(b), it returns true. why is it so?

Variables of non-primitive types in Java area really references to objects on the heap. A reference is a pointer: it tells the JVM where on the heap the object is stored. Dereferencing means: looking up the object from the reference. To call a method or access a member variable via a variable that refers to an object, the reference must be dereferenced - the JVM must find the object on the heap.

The type 'float' is a primitive type, it is not a reference, so it can't be dereferenced. You get this error because you are trying to call the equals() method on a float - you can't do that, because the variable is not an object, and doesn't have methods that you can call.