Wrapper arguments

[Uttara Rishi]

Hi Ranchers,

Please consider the following code.

 
   Short sho = new Short("-1");
   Short sh = new Short("0x1");  // Line 1
   Float f = new Float("0x10");  // Line 2
   Float f1 = new Float("100L");  //Line 3
 
  

I am getting a runtime exception on line 1 ,2 and 3.


C:\exercises\JavaExercises>java a

Exception in thread "main" java.lang.NumberFormatException: For input string: "0x1"
at java.lang.NumberFormatException.forInputString(NumberFormatException.java:48)
at java.lang.Integer.parseInt(Integer.java:456)
at java.lang.Short.parseShort(Short.java:120)
at java.lang.Short.<init>(Short.java:331)
at a.main(a.java:15)


Can somebody please explain?
What are all the legal arguments for all the Wrapper objects?
Are signs allowed?

Thanks in advance.
Uttara Rishi.

[ March 10, 2008: Message edited by: Uttara Rishi ]
[ March 10, 2008: Message edited by: Uttara Rishi ]

[Uttara Rishi]

Hi Ranchers,

I have another doubt regarding autoboxing. Please consider the following code.

 
        Integer as = 303;
Integer lo=303;
System.out.println(as==lo);// False
   

The above code compiles while the following one doesnt.

 
        Integer as = 303;
long lo=303l;
System.out.println(as==lo); // Line 1
 
   

I am getting a compiler error on line 1. Can somebody please explain?

Thanks in advance.

Uttara Rishi.

[Gaurav Arora]

0x1 only works when the jvm autoboxes the value.

  Short s = 0x1;  

will work.

I can only guess that the JVM internally parses the value to a 'short' and then calls the Short(short value) constructor.

Other than that, i'm sure you can find out the default constructors from the docs. Docs

[Gaurav Arora]

Originally posted by Uttara Rishi:
Hi Ranchers,
The above code compiles while the following one doesnt.

 
        Integer as = 303;
long lo=303l;
System.out.println(as==lo); // Line 1
 
   

I am getting a compiler error on line 1. Can somebody please explain?

Thanks in advance.

Uttara Rishi.

Compiles for me, check your compiler compliance level and try to compile manually using the -source switch.

[Uttara Rishi]

Yeah it compiles for me too. Sorry .


Uttara Rishi.

[Uttara Rishi]

Hi all,
I have one more doubt.

  
 
        Integer as = 30;
Long lo=30L;
System.out.println("==" +(as==lo)); // compiler error
System.out.println(".equals" + (as.equals(lo))); // False
 

Why are we getting a compiler error and .equals output as false.
What goes on in the equals method?

Can somebody please explain?

Thanks in advance.

Uttara Rishi.

[Rohit Garg]

Hi,
If you are trying to compare two objects then there will be no autoboxing happening. This is because of a wise decision by Sun that the code originally written without using autoboxing should not be affected.

That's the reason compiler gives an error when you try to compare the two objects which are incomparable.

Hope this helps!

Regards.

[Nabila Mohammad]

Hey in the question Uttarishi had asked..
which he thought wasnt compiling...

Can we compare an object and a primitive variable with == operator.

[Rohit Garg]

In java 1.5, yes we can compare an object and a primitive

[Rohit Garg]

but we can't compare a non wrapper with a primitive

[Gaurav Joshi]

Hi Uttara Rishi,

Integer as = 303;
long lo=303l;
System.out.println(as==lo); // Line 1

The compiler will throw error in line 1 as compiler cannot unbox Integer and Type case it to Long at the same time.

Integer as = 30;
Long lo=30L;
System.out.println("==" +(as==lo)); Line 1// compiler error
System.out.println(".equals" + (as.equals(lo))); // False
will not compile as well as Integer and Long are two different classes Although both classes extends the Number Classs you cannot equate them using ==.

[Murali Kakarla]

Hi Gaurav

Integer as = 303;
long lo=303l;
System.out.println(as==lo); // Line 1

The compiler will throw error in line 1 as compiler cannot unbox Integer and Type case it to Long at the same time.

Have you tried to compile the above code? There is no issue with the above code and it compiles without any errors and prints o/p: true

Murali...

[Uttara Rishi]

Thanks Rohit. That helped.

Murali wrote....
Integer as = 303;
long lo=303l;
System.out.println(as==lo); // Line 1

The compiler will throw error in line 1 as compiler cannot unbox Integer and Type case it to Long at the same time.

Have you tried to compile the above code? There is no issue with the above code and it compiles without any errors and prints o/p: true

Here we are talking about Integer and Long objects not the primitive long.
Hope that cleared it .


Uttara Rishi.