Why am I receiving IllegalFormatConversionException in Java for this code?

Question

I am currently working on a code that takes data from the network and print it out on a JTextArea. In between, I am trying to alignment the number based on the decimal position. This is the code that works before implementing the decimal alignment:

private static final String NewLine = System.getProperty("line.separator");
String NetString = "";
byte[] data = p.getData();
NewString += "SID:     " + BuildShort(data,4) + NewLine;
NewString += "DID:     " + BuildShort(data,6) + NewLine;

And this is the new one

NewString += String.format("%-8s%11.5f" + NewLine, "SID    : ", BuildShort(data,4));
NewString += String.format("%-8s%11.5f" + NewLine, "DID    : ", BuildShort(data,6));

which I received the error message

Exception in thread "Thread-2" java.util.IllegalFormatConversionException: f != java.lang.Integer
at java.util.Formatter$FormatSpecifier.failConversion(Unknown Source)
at java.util.Formatter$FormatSpecifier.printFloat(Unknown Source)
at java.util.Formatter$FormatSpecifier.print(Unknown Source)
at java.util.Formatter.format(Unknown Source)
at java.util.Formatter.format(Unknown Source)
at java.lang.String.format(Unknown Source)
at MT302.ParsePacket(MT302.java:97)
at MK20_DataView.run(MK20_DataView.java:261)
at java.lang.Thread.run(Unknown Source)

Do you know why I am receiving this error?

Solution 1

You are receiving the error because your BuildShort method returns an integer, and you're giving it a format pattern for a float. Just stick a double cast in front of it, it should be fine:

NewString += String.format("%-8s%11.5f" + NewLine, "SID    : ", (double)BuildShort(data,4));

Solution 2

you are formatting a floating point and not an integer. insert a %d instead of the %f and it should work

Solution 3

The error message for these format conversion errors are very poorly written by Oracle and I can't for the life of me figure out why they would have written it in such a way. Like already stated above, it means that you were trying to format an integer using a float format token.

Comments

[user1590710]

thank you, i didn't know the input value can only accept double value only

[Charles]

It doesn't have to take a double, you just told it to expect one.

[Steve Kroon]

But why doesn't the integer get promoted to a double automatically?