Problem with the Wrapper Conversion

[Faisal Fuad]

Guys...I was reading the Wapper Conversion rules and was trying to do the following, which is now giving me NumberFormatException. May be the basic part for Wrapper Class I am missing here to understand correctly. Can any one please help me to be on the right side?

public class ParseTest {
 public static void main(String []args){
	 
	//String to a Primitive
	 Double d4 = Double.parseDouble("3.14");
	 System.out.println("d4 ="+d4);
	 
	 //String to a Wrapper
	 Integer d5=Integer.valueOf("3.14");
	 System.out.println("d5 ="+d5);
 }
}

OUTPUT:

d4 =3.14
Exception in thread "main" java.lang.NumberFormatException: For input string: "3.14"
	at java.lang.NumberFormatException.forInputString(NumberFormatException.java:59)
	at java.lang.Integer.parseInt(Integer.java:467)
	at java.lang.Integer.valueOf(Integer.java:564)
	at ParseTest.main(ParseTest.java:10)

Best wishes

[dennis deems]

You are trying to create an Integer with a double value. Similar to if you had tried

int d5 = 3.14;

[Faisal Fuad]

But why that is not Widening the value for me? Isn't it an automatic process in Java? Or what i was trying to do is illegal in Java ! I know that Wrapper's second big function is convering stuff....so why can't i do that here?

Can you please show me a good example on converting a String to a Wrapper?

Thanks

[Muhammad Saifuddin]

Yes, its illegal in Java, and you can check yourself.

int d5 = 3.14;

see if you're able to compile above code?

[Faisal Fuad]

Thanks both Dennis and Muhammad...yes...certainly i can't compile that above code....but here trying to under stand how particularly Wrapper can help me, though it's second best function is to conver.

[Faisal Fuad]

Ok...let me share this...the following is clear:

//Example: Wrapped Numeric to Primitive

public class DoValueChange {
	public static void main (String [] args){
		//Creating a Wrapper Object
		Integer i2 = new Integer (42);
		
		//Converting numeric to primitive
		byte b=i2.byteValue();
		short s=i2.shortValue();
		double d = i2.doubleValue();
		
		//Print the primitive values
		System.out.println("Byte: "+b);
		System.out.println("Short: "+s);
		System.out.println("Double: "+d);
	}
}

Is there any Good example for Wrapped String to Primitive? (In this case Integer)

[John de Michele]

Faisal:

Strings aren't wrapped. If you look at the JavaDoc for Integer.valueOf(String s), you'll see that it's quite clear that if the String doesn't represent an integer value, you'll see the NumberFormatException you got. If you want to convert a String representing a floating point number, you'll have to add an intermediate step.

John.

[Campbell Ritchie]

Faisal Fuad wrote:But why that is not Widening the value for me?. . .

I know it’s late, but that is not widening. It’s narrowing. More details in the Java Language Specification.