formatting output in java using printf

Question

I have this code and I'm trying to format the output as shown below, but when I start the program and reach to printf, it stops and gives error Exception in thread "main" java.util.IllegalFormatConversionException: f != java.lang.String

variables:    
itemcode=integer
selecteditems=string
perkg=double
userkg=string
quantity-integer 
dry=string
total=double

Note: those are changeable variables into for loop.

System.out.printf("%-4d %-13s %8.2f %8.2f %-8d %-10s %8.2f %n", itemcode,
    selecteditems, per_kg, userkg, quantity, dry, total);

It would help to know the values and types of these variables — Daniel Kaplan
– Daniel Kaplan, Commented Oct 7, 2014 at 17:07
possible duplicate of Why am I receiving IllegalFormatConversionException in Java for this code? — Daniel Kaplan
– Daniel Kaplan, Commented Oct 7, 2014 at 17:10
Are you sure that per_kg, userkg total are float or double type? It seems that at leas one of them is String. — Pshemo
– Pshemo, Commented Oct 7, 2014 at 17:11
@Rustam To add line separator dependant of OS (like \r\n on windows). — Pshemo
– Pshemo, Commented Oct 7, 2014 at 17:12

azurefrog · Accepted Answer · 2014-10-07 17:19:28Z

You have defined userkg as a String, but you are trying to print it as a decimal. You need to change the type of the variable to double.

When you define a format string, you are telling java both the way you would like your variable displayed, and what type it should expect.

For instance, %8.2f requires that you give a float or double as an argument.

If instead you pass in a variable of type String, you will get an error:

e.g.

float aFloat = 0;
String notAFloat = "";
System.out.printf("%8.2f %8.2f", aFloat, notAFloat);

...gives the following error:

Exception in thread "main" 
   java.util.IllegalFormatConversionException: f != java.lang.String
at java.util.Formatter$FormatSpecifier.failConversion(Formatter.java:4045)
at java.util.Formatter$FormatSpecifier.printFloat(Formatter.java:2761)
at java.util.Formatter$FormatSpecifier.print(Formatter.java:2708)
at java.util.Formatter.format(Formatter.java:2488)
at java.io.PrintStream.format(PrintStream.java:970)
at java.io.PrintStream.printf(PrintStream.java:871)
at Scratch.main(Scratch.java:9)

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